Journal articles: 'Microwave dielectric ceramics'

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Zhou, Huanfu, Hong Wang, Minghuia Zhang, and Haibo Yang. "Microwave dielectric properties and compatibility with silver of low-fired Ba5Nb4O15 ceramics by BaCu(B2O5) addition." Journal of Materials Research 25, no. 9 (September 2010): 1793–98. http://dx.doi.org/10.1557/jmr.2010.0216.

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The influence of BaCu(B2O5) (BCB) addition on the sintering temperature and microwave dielectric properties of Ba5Nb4O15 ceramics has been investigated. The addition of small amount of BCB can effectively lower the sintering temperature of Ba5Nb4O15 ceramics from 1400 to 875 °C and induce no obvious degradation of the microwave dielectric properties. The reduced sintering temperature was attributed to the BCB liquid phase. Typically, the 1.5 wt% BCB-added Ba5Nb4O15 ceramic sintered at 875 °C for 2 h exhibited good microwave dielectric properties of Q × f = 28,655 GHz, εr = 40.2, and τf = 60 ppm/°C. The dielectric ceramic demonstrated stability against the reaction with the Ag electrode, which suggests that the ceramics could be applied in multilayer microwave devices requiring low sintering temperatures.

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Li, Yue Ming, Zong Yang Shen, Zhu Mei Wang, Hua Zhang, Yan Hong, and Run Hua Liao. "Structure and Microwave Dielectric Properties of (Ca_0.9375Sr_0.0625)_0.25 (Li_0.5Sm_0.5)_0.75TiO₃ Ceramics with B₂O₃-CuO Sintering Aids." Advanced Materials Research 284-286 (July 2011): 1442–46. http://dx.doi.org/10.4028/www.scientific.net/amr.284-286.1442.

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The B2O3-CuO oxide mixture (abbreviated as BC) was selected to lower the sintering temperature of (Ca0.9375Sr0.0625)0.25(Li0.5Sm0.5)0.75TiO3 (abbreviated as CSLST) microwave dielectric ceramics by solid sate reaction technique. The effects of BC doping amounts on the crystal structure, microstructure and microwave dielectric properties of the ceramics were investigated. For the ceramic sample with the composition of CSLST + 5 wt% BC, its sintering temperature was reduced to 1000 °C as compared to 1200 °C for pure CSLST. In addition to the obtained good microwave dielectric properties as follows: εr = 80.4, Q×f = 1380 GHz, τf = -32.89 ×10-6/°C, this ceramic was a desirable high-permittivity microwave dielectric candidate for low-temperature cofired ceramic (LTCC) applications.

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Kanareykin, Alexei D. "Low Loss Microwave Ceramic and other Microwave Dielectric Materials for Beam Physics Applications." Journal of the Russian Universities. Radioelectronics 22, no. 4 (October 1, 2019): 66–74. http://dx.doi.org/10.32603/1993-8985-2019-22-4-66-74.

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Introduction. Relativistic, high intensity and small emittance electron bunches are the basis of a future linear collider and free electron laser projects. Drive beam generation in a wakefield structure employing for power extraction and acceleration low loss dielectrics like microwave ceramics, fused silica and Chemical Vapor Deposition (CVD) diamond were considered.Objective. We report here our experimental testing of a ceramic material with extremely low loss tangent at GHz frequency ranges allowing the realization of high efficiency wakefield acceleration. We also present Barium Strontium Titanium oxides (BST) ferroelectric material, which is a critical tuning element of the 400 MHz superconducting radiofrequency (RF) tuner developed and tested by the CERN/Euclid Techlabs collaboration. The materials discussed here also include quartz and CVD diamonds that are capable of supporting the high RF electric fields generated by electron beams or pulsed high power microwaves. These materials have been optimized or specially designed for accelerator applications.Materials and methods. The ceramic materials for accelerators, commonly used for the dielectric based accelerating structures, have to withstand high gradient accelerating fields, and prevent potential charging by electron beams. Correspondingly, the ceramic materials, fused silica and CVD diamond were tested with high power wakefield accelerating structures at Argonne Wakefield Accelerator of Argonne National Laboratory. Some of the presented here ceramic materials were tested at X-band 11.4 GHz magnicon high power source.Results. Low loss microwave ceramics, fused silica, and CVD diamonds have been considered as materials for dielectric based accelerating structures to study of the physical limitations encountered driving > 100 MV/m at microwave and ~ GV/m at THz frequencies in a dielectric based wakefield accelerator. Various ceramic compositions were high power and electron beam tested at X-band 11.4 GHz magnicon power source and Argonne Wakefield Accelerator correspondingly. Special attention was paid to the CVD diamond cylindrical Ka-band 35 GHz wakefield structure development. Finally, the dielectric based structure tuning was demonstrated by varying the permittivity of the BST ferroelectric layer by temperature changes and by applying an external direct current electric field across the ferroelectric. This allows us to control the effective dielectric constant of the composite system and therefore, to control the structure frequency during operation. The same type of ferroelectric material was used for the Ferroelectric Fast Reactive tuner (FE-FRT) development. In a world first, CERN has tested the prototype FE-FRT with a superconducting cavity, and frequency tuning has been successfully demonstrated.Conclusion. Recent results on the development and experimental testing of advanced dielectric materials for accelerator applications are presented. Low loss microwave ceramics, quartz and CVD diamond are considered. We presented our experimental results on wakefield generation in microwave frequency ranges with the dielectric based accelerating structures. Special attention was paid to the experimental results on high power testing at X-band of the externally powered dielectric based components. Finally, we present here first experimental demonstration of ferroelectric tunable microwave ceramic for accelerator application, which includes both tunable dielectric wakefield accelerating structure and ferroelectric based fast high power tuner for superconducting cavities. The experimental results presented here are critical for the advanced dielectric wakefield accelerating structures and other components development intended for the future linear collider projects.

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Zeng, Qun, and Yong Heng Zhou. "Studies on Structural, Microwave Dielectric Properties, and Low-Temperature Sintering of 1.52Li₂O-0.36Nb₂O₅-1.34TiO₂ Ceramic." Key Engineering Materials 512-515 (June 2012): 1226–30. http://dx.doi.org/10.4028/www.scientific.net/kem.512-515.1226.

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The structure, microwave dielectric properties and low-temperature sintering of a new Li2O-Nb2O5-TiO2 system ceramic with the Li2O: Nb2O5: TiO2 mole ratio of 1.52: 0.36: 1.34 have been investigated in this study. The 1.52Li2O-0.36Nb2O5-1.34TiO2 (LNT) ceramic is composed of two phases, the “M-Phase” and Li2TiO3 solid solution (Li2TiO3ss) phase. This new microwave dielectric ceramic has low intrinsic sintering temperature ( ~ 1100 oC ) and good microwave dielectric properties of middle permittivity (εr ~38.6), high Q×f value up to 7712 GHz, and near zero τf value (~ 4.64 ppm/oC). In addition, the sintering temperature of the LNT ceramics could be lowered down effectively from 1100 oC to 900 oC by adding 1 wt.% B2O3. Good microwave dielectric properties of εr = 42.5, Q*f =6819 GHz and τf = 2.7 ppm/oC could be obtained at 900 oC, which indicate the ceramics would be promising candidates for low-temperature co-fired ceramics (LTCC) applications.

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Souza, José Vitor C., Pedro José Castro, Maria do Carmo de Andrade Nono, and Sergio Luiz Mineiro. "Sintering Temperature Influence on Microwave Dielectric Properties of TiO₂-ZrO₂ Ceramics." Materials Science Forum 660-661 (October 2010): 646–51. http://dx.doi.org/10.4028/www.scientific.net/msf.660-661.646.

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Dielectric ceramics have been widely investigated and used for microwave applications such as resonators and filters. The present study deals with the influence of sintering temperature on microwave dielectric properties of TiO2 ceramics with 10, 20, and 30 wt% ZrO2. Three compositions have been developed through mixing procedures and then tested for each sintering temperature: 1500 and 1400 °C. X-ray diffraction and scanning electron microscopy are carried out aiming to explain the ceramic behavior of each sample. The dielectric constants of different ceramics for both temperatures varied from 85.4 to 62.6, while their quality factor due to dielectric losses varied from 3110 to 1630. The Q decrease is attributed to the non uniform grain growth and to the obtained crystalline phases. The best microwave parameters were obtained for the ceramics sintered at 1400 °C, which can be applied in microwave circuits as dielectric resonators.

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Nono, Maria do Carmo de Andrade, Pedro José Castro, E. G. L. Rangel, and Sergio Luiz Mineiro. "Ga₂O₃-Doped ZnO-Nb₂O₅-TiO₂ Dielectric Resonators for Terrestrial and Space Telecommunications Applications." Materials Science Forum 869 (August 2016): 79–84. http://dx.doi.org/10.4028/www.scientific.net/msf.869.79.

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Dielectric ceramics find application as dielectric resonators (DRs) in communications systems operating at microwave frequencies. RDs for this application require a unique set of properties: high value of the dielectric constant, low dielectric loss and high frequency stability. This paper presents an investigation of the correlation between the dielectric properties, the characteristics of microstructure and the crystalline phases of Ga2O3-doped ZnO-Nb2O5-TiO2 ceramic system. The ceramics sintered at 1200 °C were characterized as for density, crystalline phases, microstructure and microwave dielectric properties. The results showed that these dielectric ceramics, obtained from the TiO2 anatase crystalline structure, present dielectric constant and quality factor (Q) values appropriate for their use as dielectric resonators in microwave circuits. According to the experiments, as the gallium doping has raised, the dielectric constant increased, the Q factor decreased and the temperature coefficient had a tendency to decrease to a certain extent.

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Xiong, Zhao Xian, M. Y. Zhou, Hao Xue, Hong Qiu, and F. Xiao. "Characterization of Microwave Ceramics with Low Permittivity and High Quality Factors." Key Engineering Materials 434-435 (March 2010): 244–46. http://dx.doi.org/10.4028/www.scientific.net/kem.434-435.244.

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A new type of porous ceramics, Mg2SiO4, for microwave application with low permittivity and high quality factors were prepared via gel-casting processing in this paper. Microstructure of the ceramics was observed and crystal structure of the samples was also identified. Moreover, emphasis was paid on the characterization of the microwave ceramics. Dielectric properties of the ceramics were measured by an automatic system of microwave measurement, resulting in dielectric constant of 3.51 and quality factor of 11,774 for the ceramic sample at frequency about 10GHz. Mechanical performance of the samples were also evaluated with maximal bending strength of 140MPa.

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Yang, Shuwei, Bingliang Liang, Changhong Liu, Jin Liu, Caisheng Fang, and Yunlong Ai. "Microwave Sintering and Microwave Dielectric Properties of (1–x)Ca0.61La0.26TiO3-xNd(Mg0.5Ti0.5)O3 Ceramics." Materials 14, no. 2 (January 17, 2021): 438. http://dx.doi.org/10.3390/ma14020438.

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The (1–x)Ca0.61La0.26TiO3-xNd(Mg0.5Ti0.5)O3 [(1–x)CLT-xNMT, x = 0.35~0.60] ceramics were prepared via microwave sintering. The effects of sintering temperature and composition on the phase formation, microstructure, and microwave dielectric properties were investigated. The results show that the microwave sintering process requires a lower sintering temperature and shorter sintering time of (1–x)CLT-xNMT ceramics than conventional heating methods. All of the (1–x)CLT-xNMT ceramics possess a single perovskite structure. With the increase of x, the dielectric constant (ε) shows a downward trend; the quality factor (Qf) drops first and then rises significantly; the resonance frequency temperature coefficient (τf) keeps decreasing. With excellent microwave dielectric properties (ε = 51.3, Qf = 13,852 GHz, τf = −1.9 × 10−6/°C), the 0.65CLT-0.35NMT ceramic can be applied to the field of mobile communications.

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Cai, Wei, Chun Lin Fu, Gang Chen, Xiao Ling Deng, and Kai Hua Liu. "Effects of Microwave Sintering Time on Microstructure, Dielectric, Ferroelectric Properties of Barium Zirconate Titanate Ceramics." Key Engineering Materials 602-603 (March 2014): 786–90. http://dx.doi.org/10.4028/www.scientific.net/kem.602-603.786.

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Barium zirconate titanate ceramics were prepared by microwave sintering. Effects of microwave sintering time at 2.5kW on microstructure, dielectric and ferroelectric properties of barium zirconate titanate ceramics have been investigated. The result shows that the ceramic samples sintered at 2.5kW for 15~30min are single phase perovskite structure and there is no secondary phase observed. The degree of crystallinity increases with the increase of microwave sintering time. As the microwave sintering time increases, barium zirconate titanate ceramics become more uniform and the grain size increases. The Curie temperature of the samples sintered at 2.5kW for 15min, 20min and 30min is-20°C, -10°C and-15°C, respectively. As the microwave sintering time increases, the dielectric constant of barium zirconate titanate ceramics decreases initially and then increases, and the dielectric loss decreases. Moreover, the remnant polarization of the sample increases initially and then decreases, and the coercive electric field decreases as the microwave sintering time increases.

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10

Li, Yue Ming, Ting Ting Song, Fei Hu, Run Hua Liao, and Bin Zhang. "Microwave Dielectric Properties of Ca_1-x(Li_1/2Sm_1/2)_xTiO₃ Ceramics." Advanced Materials Research 105-106 (April 2010): 238–41. http://dx.doi.org/10.4028/www.scientific.net/amr.105-106.238.

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Ca1-x(Li1/2Sm1/2)xTiO3 microwave dielectric ceramics in the x range of 0.70 ~ 0.80 were prepared by conventional ceramics fabrication technique. The crystal structure, microstructure and microwave dielectric properties were investigated. The results showed that a single orthorhombic perovskite structure formed within this x range, and the substitution of (Li1/2Sm1/2)2+ ion for Ca2+ ion in A-site has a significant influence on the microwave dielectric properties of the ceramics. With the increase of substitution of (Li1/2Sm1/2)2+ ion with 0.75, the temperature coefficient of resonant frequency τf reaches zero, and it could be attributed that the Sm and Li have a polarizability effect according to its microstructure. The Ca0.25(Li1/2Sm1/2)0.75TiO3 ceramic had a good performance with microwave dielectric properties of τf = 0 ppm/°C, εr = 105.83, and Qf = 3170 GHz.

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Peng, Rui, Yuan Xun Li, Hua Su, Yong Cheng Lu, Xue Ying Wang, Gong Wen Gan, and Gang Wang. "Relationship between the Different Amount of LMZBS Glass and Dielectric Properties of Li₂(Mg_0.96Ni_0.04)SiO₄Ceramics." Materials Science Forum 1027 (April 2021): 10–14. http://dx.doi.org/10.4028/www.scientific.net/msf.1027.10.

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The effect of different amount of LMZBS glass on the sintering behavior, microstructure and microwave dielectric properties of the Li2(Mg0.96Ni0.04)SiO4 ceramics was investigated. The synthesis of materials was based on the solid-state reaction method. The micromorphology of the composite ceramics was confirmed using scanning electron microscopy. The microwave dielectric parameters were measured by the network analyzer. The mechanism of heat transfer coming from LMZBS glass lower the densification temperature of matrix ceramic from 1150°C down to 900°C. Excellent microwave dielectric properties were obtained with 1.2 wt% LMZBS glass sintered at 900°C for 4h (εr=5.77 and Q×f=29,558 GHz at 16 GHz, τf=-14.5 ppm/°C). There was a compatibility between the composite ceramic and Ag. Therefore, the aimed ceramic has great potential value of application in the field of low temperature co-fired ceramics of millimeter-wave devices.

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Zhang, Zhi Li, Chun Xu, and Qiu Ping Liu. "Microwave Dielectric Properties of RENbO₄ (RE=Y, Yb,Ce) Ceramics." Key Engineering Materials 434-435 (March 2010): 217–20. http://dx.doi.org/10.4028/www.scientific.net/kem.434-435.217.

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In the search of more microwave dielectric materials with high-quality factor (Qf ) and high relative dielectric constant (r), RENbO4 (where RE = Y, Ce, Yb) niobate ceramics were synthesized from a solid-state ceramic route, their sintering behavior and microwave dielectric properties were investigated. All of the RENbO4 ceramics formed a single-phase fergusonite-type structure (monoclinic, with space group I2/c), except CeNbO4. They all have an excellent quality factor and dielectric constant value in range of 20 – 28, and the inherent reasons were analyzed.

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Wei, Peng Fei. "Dielectric Properties of Na₂O Doped Cao-B₂O₃-SiO₂ System Glass-Ceramics." Advanced Materials Research 750-752 (August 2013): 492–96. http://dx.doi.org/10.4028/www.scientific.net/amr.750-752.492.

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The behavior of dielectric and microwave properties against sintering temperature was been carried out on CaO-B2O3-SiO2glass-ceramics with Na2O addition by XRD and SEM. The results show that 0.5 wt.% Na2O addition is advantageous to improve the dielectric and microwave properties due to increasing the major crystalline CaSiO3. With further increasing Na2O content, α-SiO2is the predominant crystalline phase instead of CaSiO3. The CBS glass-ceramics with 0.5 wt.% Na2O sintered at 875°C has a bulk density of 2.51g·cm-3, and which possesses good dielectric properties:εr=6.2,tanδ=1.9×10-3(10 MHz) and low dielectric constant below 2×10-3over a wide frequency range. The proposed dielectrics can find applications in microwave devices, which require low dielectric loss and low dielectric constant.

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Luo, J., Z. Y. Pang, Y. S. Lin, and Zhao Xian Xiong. "Influences of MnCO₃ Doping on Processing Parameters and Dielectric Properties of ZnNb₂O₆ Microwave Ceramics." Key Engineering Materials 280-283 (February 2007): 23–26. http://dx.doi.org/10.4028/www.scientific.net/kem.280-283.23.

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MnCO3 was added into ZnNb2O6 ceramics to obtain excellent microwave dielectric properties. The samples were prepared by conventional solid-state reaction method. The effects of the amount of MnCO3 on sintering temperatures, ceramic densities and contraction were systematically investigated. The crystalline structure of ceramic body was analyzed by XRD. The ceramic microstructure was observed by SEM. The dielectric properties of ZnNb2O6 ceramics were measured by a vector network analyzer at microwave frequency, which showed: er = 22.65, Q×f = 36700 GHz (loaded value) and tf = -40 ppm/°C.

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Peng, Sen, Chen Li, Chao Tang, Sheng Liu, Shengxiang Huang, Leilei Qiu, and Lianwen Deng. "Crystal Structures and Microwave Dielectric Properties of Novel MgCu2Nb2O8 Ceramics Prepared by Two-Step Sintering Technique." Materials 15, no. 22 (November 15, 2022): 8053. http://dx.doi.org/10.3390/ma15228053.

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In this work, novel MgCu2Nb2O8 (MCN) ceramics were synthesized by the two-step sintering (TSS) technique, and the phase composition, crystal structures, and microwave dielectric properties were comprehensively studied. X-ray diffraction (XRD) and Raman analysis demonstrated that MCN ceramics are multi-phase ceramics consisting of MgNb2O6 and CuO phases. X-ray photoelectron spectroscopy (XPS) was utilized to investigate the chemical composition and element valence of MgCu2Nb2O8 ceramics. Scanning electron microscopy (SEM) analysis demonstrated dense microstructures in the MCN ceramics prepared at a sintering temperature of 925 °C. The microwave dielectric properties were largely affected by the lattice vibrational modes and densification level of the ceramics. The outstanding microwave dielectric properties of εr = 17.15, Q × f = 34.355 GHz, and τf = −22.5 ppm/°C were obtained for the MCN ceramics sintered at 925 °C, which are results that hold promise for low temperature co-fired ceramic (LTCC) applications.

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VARGHESE, JOBIN, MATHEU PRESUME, KUZHICHALIL PEETHAMBHARAN SURENDRAN, and MAILADIL THOMAS SEBASTIAN. "A NOVEL DIELECTRIC CERAMIC FOR MICROWAVE PASSIVE CIRCUITS." International Journal of Modern Physics: Conference Series 22 (January 2013): 153–58. http://dx.doi.org/10.1142/s2010194513010040.

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The tetragonal Ca 9 Nd 2 W 4 O 24 (CNW) ceramic was prepared by the conventional solid state ceramic route and their dielectric properties were investigated in the radio and microwave frequencies. The CNW ceramics sintered at 1450 °C for 4 h showed a densification 92 % with εr = 16 and tanδ = 0.004 at 15.1 GHz. The thermal conductivity of ceramic at room temperature was found to be 1.6 W m−1K−1 and coefficent of thermal expansion of CNW ceramics was 4.2 ppm/°C measured in the range of 25 to 600 °C. The dielectric and thermal properties of CNW ceramic are reported for the first time.

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Xu, Shangrui, Juan Jiang, Zelai Cheng, Xiangyi Chen, Shikuan Sun, Dawei Wang, and Tianjin Zhang. "Temperature Stable, High-Quality Factor Li2TiO3-Li4NbO4F Microwave Dielectric Ceramics." Crystals 11, no. 7 (June 25, 2021): 741. http://dx.doi.org/10.3390/cryst11070741.

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In this work, (1-x)Li2TiO3-xLi4NbO4F ceramics were prepared by the conventional solid-state ceramic route. With the increase of Li4NbO4F content, the phase structure transformed from ordered monoclinic to disordered cubic. By increasing Li3NbO4F content, the temperature coefficient of resonant frequency (τf) was successfully adjusted closer to zero, while the dielectric constant (εr) and microwave quality factor (Qf) decreased to some degree. Outstanding microwave dielectric properties with a εr = 18.7, Qf = 61,388 GHz (6.264 GHz), and τf = 0.9 ppm/°C were obtained for 0.9Li2TiO3-0.1Li4NbO4F ceramics sintered at 1050 °C for 2 h, which indicated that these ceramics are suitable for practical applications in the field of microwave substrates and components.

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Souza, José Vitor C., Pedro José Castro, Maria do Carmo de Andrade Nono, and A. R. Siqueira. "Study of ZrO₂-TiO₂ Ceramics with SnO₂, SrO₂ and Nb₂O₅ Additives for Dielectric Resonator Application." Materials Science Forum 591-593 (August 2008): 381–86. http://dx.doi.org/10.4028/www.scientific.net/msf.591-593.381.

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This paper presents a systematic study about ceramics made of zirconium oxide and titanium oxide (ZrO2-TiO2) doped with tin oxide (SnO2), strontium oxide (SrO2) and niobium oxide (Nb2O5). These ceramics can be applied as dielectric resonators in microwave systems for telecommunications. For a good microwave performance, these ceramics must reach some parameter values as high dielectric constant and high quality factor due to the dielectric losses. The ceramics were manufactured using suitable powder mixtures of ZrO2-TiO2 with additions of 1 % of SnO2, SrO2 and Nb2O5, resulting in four different kinds of samples for analysis. The samples were compacted by an uniaxial (190 MPa) and an isostatic (300 MPa) pressing, sintered at 1200 °C for 3 hours, characterized in the chemical compound formation using X-ray Diffraction (XRD) and scanned for microstructure densification degree and grain distribution analysis in Scanning Electron Microscopy (SEM). The dielectric parameters were measured using a microwave system. The main goal of present procedure is manufacture ceramic materials for promising application as dielectric resonators.

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He, Tiancheng, Caihuan Lv, Wenhao Li, Guohua Huang, Zhihui Hu, and Jianmei Xu. "The Dielectric Constant of Ba6−3x(Sm1−yNdy)8+2xTi18O54 (x = 2/3) Ceramics for Microwave Communication by Linear Regression Analysis." Materials 13, no. 24 (December 16, 2020): 5733. http://dx.doi.org/10.3390/ma13245733.

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The electronics related to the fifth generation mobile communication technology (5G) are projected to possess significant market potential. High dielectric constant microwave ceramics used as filters and resonators in 5G have thus attracted great attention. The Ba6−3x(Sm1−yNdy)8+2xTi18O54 (x = 2/3) ceramic system has aroused people’s interest due to its underlying excellent microwave dielectric properties. In this paper, the relationships between the dielectric constant, Nd-doped content, sintering temperature and the density of Ba6−3x(Sm1−yNdy)8+2xTi18O54 (x = 2/3) ceramics were studied. The linear regression equation was established by statistical product and service solution (SPSS) data analysis software, and the factors affecting the dielectric constant have been analyzed by using the enter and stepwise methods, respectively. It is found that the model established by the stepwise method is practically significant with Y = −71.168 + 6.946x1 + 25.799x3, where Y, x1 and x3 represent the dielectric constant, Nd content and the density, respectively. According to this model, the influence of density on the dielectric constant is greater than that of Nd doping concentration. We bring the linear regression analysis method into the research field of microwave dielectric ceramics, hoping to provide an instructive for the optimization of ceramic technology.

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RAMANA, M. VENKATA, S. ROOPAS KIRAN, N. RAMAMANOHAR REDDY, K. V. SIVA KUMAR, V. R. K. MURTHY, and B. S. MURTY. "SYNTHESIS OF LEAD FREE SODIUM BISMUTH TITANATE (NBT) CERAMIC BY CONVENTIONAL AND MICROWAVE SINTERING METHODS." Journal of Advanced Dielectrics 01, no. 01 (January 2011): 71–77. http://dx.doi.org/10.1142/s2010135x11000094.

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Dielectric studies were carried out on a lead free Sodium Bismuth Titanate, NBT, ( Na 0.5 Bi 0.5 TiO 3) composition. The material was synthesized by conventional ceramic method (CS) and microwave sintering (MS). The presence of single phase has been confirmed by X-ray diffraction and scanning electron microscopy of NBT ceramic. The later technique (MS) resulted in material with high density, dielectric properties and improved microstructure. The transition temperature was observed slightly higher for microwave sintered (MS) material. Longitudinal modulus measurements are very sensitive property to identify the phase transitions in ceramics. Longitudinal modulus (L) measurements were also employed on these samples in the frequency 136 kHz and can be studied in the wide temperature range 30°C to 400°C. The elastic behavior (L) showed a break at two temperatures (~200°C and 350°C) in both the conventional and microwave sintered ceramics. In NBT ceramics, permittivity anomalies are connected to modulus anomalies. The results are correlated with the dielectric measurements. This behavior explained in the light of structural phase transitions in the ferroelectric ceramics.

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Miao, Xi Geng, Fabrizia Ghezzo, Jing Jing Liu, Zhi Ya Zhao, and Ruo Peng Liu. "Use of a Dielectric Glass to Join Dielectric Ceramics for Microwave Filters." Advanced Materials Research 787 (September 2013): 316–21. http://dx.doi.org/10.4028/www.scientific.net/amr.787.316.

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Joining of ceramics with glasses has been widely used for artificial teeth, solid oxide fuel cells, electrical devices, high temperature ceramic filters, structural ceramic components for aeronautic engineering, nuclear reactors, and other applications. This study aimed to explore the possibility of using a dielectric glass to connect a dielectric ceramic resonator to a dielectric ceramic support, in order to make miniaturized microwave filters characterized by higher temperature and environmental stability and low dielectric loss. A mixed powder having Bi2O3-SiO2-Al2O3-MgO-ZnO-CaO glass as a matrix and SiO2-Al2O3-MgO as a ceramic filler was used to join the dielectric ceramic resonators made of the CaTiO3-NdAlO3-Al2O3 system to the dielectric ceramic supports made of the ZnO-TiO2-Al2O3-MgO system. In spite of the strong interfacial bonding obtained, microcracks were observed in the joined bodies, suggesting that not only the dielectric loss of the bonding layer but also the match of the thermal expansion coefficients of the components to be joined should be carefully considered and tailored.

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Thomazini, Daniel, Maria Virginia Gelfuso, Gabriel Moreira Lima, and José Antônio Eiras. "Microstructural and Dielectric Properties of Conventional and Microwave Sintered CaCu₃Ti₄O₁₂ Ceramics." Materials Science Forum 727-728 (August 2012): 1063–68. http://dx.doi.org/10.4028/www.scientific.net/msf.727-728.1063.

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ts well known that CaCu3Ti4O12(CCTO) ceramic presents high dielectric constants, which makes it a strong candidate to be used in microelectronic devices. Several routes were proposed to obtain CCTO crystalline phase, influencing in microstructure and sintering conditions of the ceramics. In this study CCTO powders were produced by a new chemical route, providing reduction on hold time and sintering temperature. Furthermore, the sintering was performed in conventional and microwave oven that produced different microstructures. In this way, the microstructure and dielectric properties of these ceramics were evaluated and compared, showing the higher values of dielectric constant due to lower grain size and reduced copper-rich phase on grain boundary presented by microwave sintered ceramics.

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Gu, Yong Jun, Jin Liang Huang, Wei Hu, Qian Li, Li Hua Li, and Hui Xu. "Low Temperature Sintering of Ca_0.6La_0.8/3TiO₃-Li_0.5Nd_0.5TiO₃ Ceramics with ZnO-B₂O₃-SiO₂ Glass Addition." Advanced Materials Research 335-336 (September 2011): 956–59. http://dx.doi.org/10.4028/www.scientific.net/amr.335-336.956.

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The sintering behaviors and microwave dielectric properties of the Ca0.6La0.8/3TiO3-Li0.5Nd0.5TiO3 (abbreviated CLLNT) ceramics doped by small amounts of ZnO-B2O3-SiO2 glass were investigated in this paper. The adding of ZnO-B2O3-SiO2 glass improved the densifications of the CLLNT ceramics and the sintering temperature of the CLLNT ceramic had been efficiently lowered to 1050°C. Especially, the 8wt% ZnO-B2O3-SiO2 glass doped CLLNT ceramic sintered at 1050°C for 3 h has optimum microwave dielectric properties of Kr=89, Q×f=1445GHz, and TCF=11.4 ppm/°C and it should be a suitable candidate for LTCC applications.

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Xiong, Zhao Xian, X. Xue, Hong Qiu, C. Zhang, C. Fang, J. Luo, D. Y. Bao, et al. "Microwave Dielectric Ceramics and Devices for Wireless Technologies." Key Engineering Materials 368-372 (February 2008): 154–58. http://dx.doi.org/10.4028/www.scientific.net/kem.368-372.154.

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In this paper, several kinds of synthesis techniques were adopted; not only conventional solidstate reaction method but also solution synthesis techniques, including co-precipitation and hydrothermal synthesis, in addition to the gel-casting for complex shape of ceramic components and tape-casting of large scale thin plate for microwave IC. Different kinds of microwave ceramics were prepared, such as materials with low permittivity and high quality factor, moderate permittivity and good quality factor, and, high permittivity and reasonable quality factor, in addition to near zero of temperature coefficient of resonance frequency. Series of microwave devices were developed, for examples, dielectric resonators, dielectric filters, GPS antennas, communication connectors, and thin substrates for microwave IC.

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Xu, Jian Mei, Dong Xiang Zhou, Dao Li Zhang, Guo Hua Huang, and Shu Ping Gong. "Microwave Dielectric Properties of Mn-Doped Ba_4.5Sm₉Ti₁₈O₅₄ Ceramics." Key Engineering Materials 280-283 (February 2007): 5–8. http://dx.doi.org/10.4028/www.scientific.net/kem.280-283.5.

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The different amounts of manganese dioxide were doped to Ba4.5Sm9Ti18O54 (BST)ceramics. It was found that the doping sequence of Mn had serious influences on the microwave dielectric properties of the BST ceramics. When manganese dioxide was added before the mixtures were calcined, the dielectric properties of ceramics were poor and decreased with the increase of the Mn content. When the Mn content was between 2.0wt% and 3.0wt%, the BST ceramics had no microwave characteristic. But adding manganese dioxide in a range of 0.0 to 1.0wt% after the mixtures were calcined enhanced the microwave dielectric properties of the BST ceramics. When the Mn content changed from 0 to 1.0wt%, the microwave properties of the BST ceramics increased, but the microwave properties decreased while the Mn content was over 1.0wt%. The ceramics with 3.0wt% Mn content had also no microwave characteristic. The optimum microwave dielectric properties were as follows: εr=76, Q·f=7280,τf=-3.6ppm/k.

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Palaimiene, Edita, Jan Macutkevič, Jūras Banys, Algirdas Selskis, Natalia Apanasevich, Alexander Kudlash, Aliaksei Sokal, and Konstantin Lapko. "Phosphate Ceramics with Silver Nanoparticles for Electromagnetic Shielding Applications." Materials 15, no. 20 (October 13, 2022): 7100. http://dx.doi.org/10.3390/ma15207100.

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Ceramic composites with nanoparticles are intensively investigated due to their unique thermal, mechanic and electromagnetic properties. In this work, dielectric properties of phosphate ceramics with round silver nanoparticles of various sizes were studied in the wide frequency range of 20 Hz–40 GHz for microwave shielding applications. The percolation threshold in ceramics is close to 30 wt.% of Ag nanoparticles content and it is higher for bigger-sized nanoparticles. The microwave complex dielectric permittivity of ceramics above the percolation threshold is rather high (ε′ = 10 and ε″ = 10 at 30 GHz for ceramics with 50 wt.% inclusions of 30–50 nm size, it corresponds to almost 61% absorption of 2 mm-thickness plate) therefore these ceramics are suitable for microwave shielding applications. Moreover, the microwave absorption is bigger for ceramics with a larger concentration of fillers. In addition, it was demonstrated that the electrical transport in ceramics is thermally activated above room temperature and the potential barrier is almost independent of the concentration of nanoparticles. At very low temperature, the electrical transport in ceramics can be related to electron tunneling.

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27

Park, Min Kyu, Ha Neul Kim, Kee Sung Lee, Seung Su Baek, Eul Son Kang, Do Kyung Kim, and Yong Kee Baek. "Effect of Microstructure on Dielectric Properties of Si₃N₄ at Microwave Frequency." Key Engineering Materials 287 (June 2005): 247–52. http://dx.doi.org/10.4028/www.scientific.net/kem.287.247.

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Silicon nitride (Si3N4) has been researched intensively because of superior mechanical properties up to high temperature. The mechanical properties of Si3N4 are strongly related to microstructure. The microstructure control of silicon nitride is well known to be a key issue for tailoring the mechanical properties of structural ceramics. This work was performed to reveal the effect of microstructure on dielectric properties at microwave frequency. Three starting powders were used fine, course a-Si3N4 and b-Si3N4. Sintering additives, 5 wt.% Y2O3, 2 wt.% Al2O3 and 1 wt.% MgO were mixed with each starting powder. Si3N4 ceramic with different b/a phase specimen were obtained by hot pressing. The post-resonator method was used for the measurement of dielectric properties, dielectric constant (e′) and dielectric loss (tand), at microwave frequency range. Silicon nitride ceramics show dielectric constant of 8.1 – 8.6 and dielectric loss 1.1 x 10-3 – 5.6 x 10-3. The effect of grain size and the role of phase on microwave dielectric properties are discussed.

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Song, Kai Xin, Zhi Hua Ying, Liang Zheng, Zheng Liu, and Hui Bin Qin. "Phase Evolution and Microwave Dielectric Properites in the Systems of (Mg_1-xCa_x)₂SiO₄ Ceramics." Advanced Materials Research 152-153 (October 2010): 801–4. http://dx.doi.org/10.4028/www.scientific.net/amr.152-153.801.

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In this paper, the microwave dielectric properties in the systems of nominal chemical composition (Mg1-xCax)2SiO4 (0≤x≤0.5)ceramics were investigated, together with their phase evolution. With the increase of x value, the major phase in the ceramic systems gradually changes from Mg2SiO4 to MgCaSiO4, besides with the some secondary phase of MgSiO3 and Ca2MgSi2O7, The relative dielectric constant in the systems of ceramics gradually increased from 6.8 to 8.7. The quality factor of value was well improved, and especially, the absolute value of the ceramic resonant frequency of temperature coefficients was optimized to reach zero, from -61 to +3 . The best optimum chemical composition was equal to 0.4, where the microwave dielectric properties was = 7.2, = 24,170 GHz, = +5 .

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29

Xiao, Yuan, Xiao Gu Huang, and Qi Tu Zhang. "Studies on BaO-CeO₂-TiO₂ Microwave Dielectric Ceramics." Advanced Materials Research 197-198 (February 2011): 323–27. http://dx.doi.org/10.4028/www.scientific.net/amr.197-198.323.

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BaO-CeO2-TiO2 microwave dielectric ceramics with the different content of TiO2 were fabricated by a solid-state reaction method using BaCO3, CeO2, TiO2 powders as starting materials in view of the dispute. The sintering characteristics, phase composition, micro-structures and microwave dielectric properties of BaO-CeO2-nTiO2 microwave dielectric ceramics with different n values sintered at different temperatures were investigated. The results showed that the sintering temperature of BaO-CeO2-nTiO2 microwave dielectric ceramics was lower (< 1300°C), and CeO2 didn’t tend to form polynary compounds. When n = 3, the sintered ceramics had excellent dielectric properties: εr ≈40.3, tanδ ≈1.02×10-3 (1 MHz); εr ≈ 41.2, Q•f =19922GHz (6.865 GHz), τf = +22 ppm/°C .

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Zhang, Qin, Hua Su, and Xiaoli Tang. "Effects of Cu substitution on microstructures and microwave dielectric properties of Li₂ZnSiO₄ ceramics." MATEC Web of Conferences 355 (2022): 01025. http://dx.doi.org/10.1051/matecconf/202235501025.

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Herein, the influence of Cu2+ substitution on the phase composition, bulk density, microstructures, and microwave dielectric properties of Li2CuxZn1−xSiO4 (0 ≤ x ≤ 0.06) ceramics prepared by a solid-state reaction were investigated. The results of XRD and mapping showed that Cu2+ substitution can avoid the influence of secondary phase on the properties of samples. According to the analysis of bulk density, microstructure and microwave dielectric properties, a proper amount of Cu substitution not only improved the sintering characteristics of Li2CuxZn1−xSiO4 ceramics, reduced the densification temperature from 1250 °C to 950 °C, but also increased the Q×f value. Furthermore, Cu2+ substitution also improved the temperature stability of the samples. Particularly, the Li2Cu0.04Zn0.96SiO4 ceramics sintered at 950 °C for 5 h possessed excellent microwave dielectric properties: εr = 5.624, Q×f = 12,764 GHz, and τf = −77 ppm/°C, exhibiting a potential for the low temperature co-fired ceramic applications.

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31

Luo, Chunya, Zhichao Ma, Laisheng Hu, Mingzhe Hu, and Xiaomin Huang. "Research on sintering behavior and microwave dielectric property of (Mg0.95Ca0.05)TiO3 ceramics for cross coupling filter." Modern Physics Letters B 29, no. 34 (December 20, 2015): 1550220. http://dx.doi.org/10.1142/s0217984915502206.

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The microwave dielectric properties of [Formula: see text]–[Formula: see text] (abbreviated as 95MCT hereafter) ceramics have been studied for application in dielectric cross coupling filters. [Formula: see text] and [Formula: see text] were selected as liquid sintering aids to lower the sintering temperature and enhance the Qf value of 95MCT and simultaneously we varied the mole ratio of [Formula: see text] to tune the microwave dielectric properties of 95MCT. When the [Formula: see text] mole ratio was 1.5 and the co-doping content was 0.25 wt.%, the optimal sintering temperature of 95MCT ceramic could be lowered from [Formula: see text] to [Formula: see text] and the Qf value could be improved by about 7.7%. The optimal microwave dielectric properties obtained under this condition were Qf = 72730 GHz (6.8 GHz), [Formula: see text] and [Formula: see text], which demonstrated great potential usage in ceramic industry. High values of Qf ceramic were used to design the dielectric cross coupling filter. The dielectric filter measured at 2.35 GHz exhibited a 6.7% bandwidth (insert loss [Formula: see text] dB) of center frequency.

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32

Li, Jia-mao, and Tai Qiu. "Microwave sintering of Ca0.6La0.2667TiO3 microwave dielectric ceramics." International Journal of Minerals, Metallurgy, and Materials 19, no. 3 (March 2012): 245–51. http://dx.doi.org/10.1007/s12613-012-0546-x.

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33

GEORGE, S., V. K. SAJITH, M. T. SEBASTIAN, S. RAMAN, and P. MOHANAN. "SYNTHESIS AND MICROWAVE DIELECTRIC PROPERTIES OF Li2MgSiO4 CERAMICS PREPARED USING CITRATE GEL ROUTE." Journal of Advanced Dielectrics 01, no. 02 (April 2011): 209–13. http://dx.doi.org/10.1142/s2010135x11000203.

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The comparison of the low temperature sintering and the microwave dielectric properties of Li2MgSiO4 (LMS) ceramics prepared by citrate gel (CG) route and solid state (SS) ceramic route are discussed in this paper. The LMS prepared using CG route sintered at 1175°C/2 h has εr = 5.3 and tan δ = 1 × 10−3 at 9 GHz. The sintering temperature of LMS is lowered to 950°C with the addition of 5 wt% lithium magnesium zinc borosilicate glass and has εr = 5.6 and tan δ = 2 × 10-3 at 9 GHz. The amount of glass required to lower the sintering temperature of ceramics prepared using CG are slightly higher than that of SS ceramic route. The LMS ceramics prepared using SS ceramic route shows excellent microwave dielectric properties with low sintering temperature compared to CG route.

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34

Tang, Bin, Xing Zhang, Zixuan Fang, Qinglin Liu, and Shuren Zhang. "Preparation and characterization of (Co0:3Zn0:7)(Ti1–xSnx)Nb2O8 microwave dielectric ceramics." Materials Science-Poland 35, no. 2 (July 26, 2017): 405–11. http://dx.doi.org/10.1515/msp-2017-0042.

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Abstract Zn0.7Co0.3(Ti1-xSnx)Nb2O8 (x = 0.1, 0.15, 0.2, 0.25, 0.3, 0.35) microwave ceramics were prepared by traditional solidstate reaction method. The influences of Sn substituted for Ti on the phase constitution, crystal structure and microwave dielectric properties of Zn0.7Co0.3(Ti1-xSnx)Nb2O8 ceramics were discussed. The XRD patterns revealed the main phase of ZnTiNb2O8 and little content of Zn0.17Ti0.5Nb0.33O2 secondary phase. With further substitution of Sn, the lattice constant, volume and apparent density of the ceramics increased, the ceramic structure reached a maximal compactness at x = 0.2 which was shown on SEM. Tremendous improvement of Q × f and a declining trend of Ɛr and τf were obtained with increasing x value. Appropriate substitution value (x = 0.10) would ensure excellent microwave dielectric properties (Ɛr = 34.1, Q × f = 40562 GHz, τf =-5 ppm/°C) of the ceramics sintered at 1080 °C.

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Gu, Yong Jun, Jin Liang Huang, Xiang Ju Han, Qian Li, Xiao Wang, and Hui Xu. "Effects of LiF on Sintering Temperature and Microwave Dielectric Properties of (Ca_0.3La_0.4/3)(Li_0.25Nd_0.25)TiO₃ Ceramics Doped by ZnO-B₂O₃- SiO₂ Glass." Materials Science Forum 675-677 (February 2011): 155–58. http://dx.doi.org/10.4028/www.scientific.net/msf.675-677.155.

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The sintering behaviors and microwave dielectric properties of the (Ca0.3La0.4/3)(Li0.25Nd0.25)TiO3 (abbreviated CLLNT) ceramics doped by small amounts of ZnOB2O3- SiO2 glass and LiF were investigated in this paper. The combination adding of ZnO-B2O3- SiO2 glass and LiF improved the densifications of the CLLNT ceramics and the sintering temperature of the CLLNT ceramics were efficiently lowered from 1400°C to 1000°C. Especially, the 4.0wt% ZnO-B2O3-SiO2 glass and 1.0wt% LiF doped CLLNT ceramic sintered at 1000°C for 3h has optimum microwave dielectric properties of Kr=97, Q×f=1286GHz, and TCF=43 ppm/°C, which enable it a suitable candidate for LTCC applications.

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Li, Chunchun, Xiaoyong Wei, Haixue Yan, and Michael J. Reece. "Effects of zinc substitution on the dielectric properties of Ca5Nb4TiO17 microwave ceramics." Journal of Advanced Dielectrics 03, no. 04 (October 2013): 1320003. http://dx.doi.org/10.1142/s2010135x13200038.

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Ca 5-x Zn x Nb 4 TiO 17 ceramics with 0 ≤ x ≤ 0.4 were prepared through a solid-state reaction method. Effects of zinc substitution on sintering behavior and microwave dielectric properties of Ca 5 Nb 4 TiO 17 ceramics were investigated. The sintering temperature was significantly lowered from 1480°C for pure Ca 5 Nb 4 TiO 17 to 1260°C for x = 0.4. The microwave dielectric properties are strongly correlated with the composition. It is worth noting that the temperature coefficient of resonant frequency (τf) displays a tendency toward positive value, ranging from −126.4 ppm/°C to −8.6 ppm/°C. A temperature stable microwave ceramic with dielectric constant of 52 and Q × f value of 9937 GHz is achieved at x = 0.4 and is a potential candidate for application as cores in dielectrically loaded antennas.

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37

Wu, Mengjuan, Jundan Chen, and Yingchun Zhang. "Crystal structure and microwave dielectric characteristics of Zr-substituted Ni0.5Ti0.5NbO4 ceramic." Functional Materials Letters 12, no. 03 (May 16, 2019): 1950020. http://dx.doi.org/10.1142/s1793604719500206.

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Ni[Formula: see text](Ti[Formula: see text]Zrx)NbO4 microwave dielectric ceramics were prepared via the conventional solid-state reaction route. The phase transitions and microstructure were analyzed using X-ray powder diffraction and scanning electron microscopy. For [Formula: see text], the Ni[Formula: see text](Ti[Formula: see text]Zrx)NbO4 ceramics exhibited coexistence of rutile and wolframite phase. The microwave dielectric properties were strongly related to the density, sintering condition, and chemical composition of samples. The Zr-substitution could inhibit the abnormal grain growth effectively which reduced the ceramic dielectric loss. When [Formula: see text] increased from 0 to 0.3, the [Formula: see text] values of Ni[Formula: see text](Ti[Formula: see text]Zrx)NbO4 ceramics increased from 7294[Formula: see text]GHz to 21798[Formula: see text]GHz, but the second phase caused the decrease of dielectric constant to 35.73. For Ni[Formula: see text](Ti[Formula: see text]Zr[Formula: see text]NbO4 ceramics, [Formula: see text] can be achieved when [Formula: see text].

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Chen, Guo Zhi, Guo Tong Chen, Jian Sun, and Jing Miao. "Research on Mechanical Design with Beidou GPS Navigation Antenna Design Terminal." Applied Mechanics and Materials 345 (August 2013): 416–20. http://dx.doi.org/10.4028/www.scientific.net/amm.345.416.

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With advances in technology and machinery manufacturing technology, the satellite navigation system plays a more and more important role in the modern society. People demand increasingly for satellite navigation. Satellite navigation is increasingly used in military systems, so military and civilian value is higher and higher. For the satellite signal reception, microstrip antenna plays an indispensable role. As the mechanical design of microstrip antenna is simple, easy manufacture, low cost, smaller size, lighter weight, with the overall unity of active devices and integrated circuit, etc. The successful development of high dielectric constant ceramic material enables the area of microstrip antenna to narrow several times. Microwave dielectric ceramics material has some merits such as high dielectric constant, thermal stability and excellent characteristics of small dielectric loss. Different dielectric constant substrate can be prepared through changing and doping modification of process parameters, including the relative dielectric constant of microwave dielectric ceramics for more than a few dozens which can be used for different microwave frequencies. Those are important reasons for promoting the development of microstrip antenna.

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Ouchi, Hiromu, and Syunichiro Kawashima. "Dielectric Ceramics for Microwave Application." Japanese Journal of Applied Physics 24, S2 (January 1, 1985): 60. http://dx.doi.org/10.7567/jjaps.24s2.60.

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Nenasheva, E. A., and N. F. Kartenko. "High dielectric constant microwave ceramics." Journal of the European Ceramic Society 21, no. 15 (January 2001): 2697–701. http://dx.doi.org/10.1016/s0955-2219(01)00348-x.

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Shi, Liang, Cheng Liu, and Huaiwu Zhang. "Effects of W6+ substitution on the microwave dielectric properties of Ce2Zr3(MoO4)9 ceramics." Journal of Advanced Dielectrics 09, no. 06 (December 2019): 1950049. http://dx.doi.org/10.1142/s2010135x19500498.

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Low temperature sintered Ce2Zr3([Formula: see text][Formula: see text][Formula: see text] (marked as CZMW) ceramics were synthesized via the conventional solid-state reaction method. X-ray diffraction results showed that the CZMW ceramics belonged to a Trigonal system with R-3C space group, and without any impure phase formation. The experimental facts revealed that the density and grain morphology greatly affected the microwave dielectric properties. The samples sintered at 825∘C exhibited good microwave dielectric properties: [Formula: see text], [Formula: see text][Formula: see text]GHz (at 11.3[Formula: see text]GHz) and a satisfactory [Formula: see text] ([Formula: see text]1.5[Formula: see text]ppm/∘C) value. It is suggested that the CZMW ceramics are suitable for low-temperature co-fired ceramic (LTCC) applications in microwave devices.

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Nishimura, Yutsuki, Masaki Yasuoka, Takaaki Nagaoka, Yoshiaki Kinemuchi, and Koji Watari. "Microwave Sintering BaTiO₃ Ceramics Using Liquid Phase Sintering." Key Engineering Materials 317-318 (August 2006): 131–34. http://dx.doi.org/10.4028/www.scientific.net/kem.317-318.131.

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Microwave sintering is a process in which target materials absorb microwaves and heat themselves from the inside. When microwave energy is effectively absorbed by the material, energy consumption for the sintering can be reduced. Our study is focused on the microwave sintering of BaTiO3 to more rapidly obtain dense ceramics with specific characteristics. For BaTiO3-based electronic components, the sintering temperature is too high for manufacture, so various additives are used to decrease the sintering temperature without undue worsening of the electrical characteristics. In this work, during microwave sintering, BaCO3, H3BO3, BaB2O4 and LiF were added to form a liquid. The effects of the amount of liquid phase on density and dielectric properties were investigated. BaTiO3 sintered with BaCO3 and H3BO3 showed dielectric properties, whereas BaTiO3 sintered with BaB2O4 had semiconducting properties with PTCR characteristics. Also, LiF-added BaTiO3 indicated a dielectric constant in which the peak shifts to lower temperatures with higher LiF concentrations.

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Miao, Xi Geng, Jing Jing Liu, Fabrizia Ghezzo, Xiao Wei Fang, Zhi Ya Zhao, and Ruo Peng Liu. "Brief Introduction of Microwave Ceramics Developed in our Labs for Dielectric Resonators." Advanced Materials Research 887-888 (February 2014): 294–98. http://dx.doi.org/10.4028/www.scientific.net/amr.887-888.294.

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Microwave filters require dielectric ceramic resonators attached to ceramic supports via joining. Among the BaTiO3, CaTiO3, and Ba2Ti9O20based-dielectric ceramics prepared in our labs., the CaTiO3ceramics modified with NdAlO3and Al2O3gave satisfactory dielectric properties: dielectric constant DK = 40.69, quality factor Qxf = 18842 GHz (fo = 6.551 GHz), and frequency temperature coefficient tf= 2.542 ppm °C-1. For replacing the hard-to-sinter Al2O3based-ceramic supports, a glass-ceramic of the SiO2-B2O3-P2O5-ZnO system was developed, leading to a low sintering temperature of 900 °C, and a low dielectric constant (<4). Finally, a Bi2O3-ZnO-SiO2-Al2O3-CaO glass was used as a sealing agent to replace the traditional gluing consisting of an adhesive. The present work hinters that with proper sintering aids, one can produce multilayered and integrated resonators with and without embedded passive elements.

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Weng, Min-Hang, Chihng-Tsung Liauh, Shueei-Muh Lin, Hung-Hsiang Wang, and Ru-Yuan Yang. "Sintering Behaviors, Microstructure, and Microwave Dielectric Properties of CaTiO3–LaAlO3 Ceramics Using CuO/B2O3 Additions." Materials 12, no. 24 (December 13, 2019): 4187. http://dx.doi.org/10.3390/ma12244187.

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The effect of CuO/B2O3 additions on the sintering behaviors, microstructures, and microwave dielectric properties of 0.95LaAlO3–0.05CaTiO3 ceramics is investigated. It is found that the sintering temperatures are lowered efficiently from 1600 °C to 1350 °C, as 1 wt % CuO, 1 wt % B2O3, and 0.5 wt % CuO +0.5 wt % B2O3 are used as the sintering aids due to the appearance of the liquid phase sintering. The microwave dielectric properties of 0.95LaAlO3–0.05CaTiO3 ceramics with the sintering aid additions are strongly related to the densification and the microstructure of the sintered ceramics. At the sintering temperature of 1300 °C, the 0.95LaAlO3–0.05CaTiO3 ceramic with 0.5 wt % CuO + 0.5 wt % B2O3 addition shows the best dielectric properties, including a dielectric constant (εr) of 21, approximate quality factor (Q × f) of 22,500 GHz, and a temperature coefficient of the resonant frequency (τf) of −3 ppm/°C.

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Davies, P. K. "Polytypic intergrowths in barium polytitanate dielectric ceramics." Proceedings, annual meeting, Electron Microscopy Society of America 44 (August 1986): 456–59. http://dx.doi.org/10.1017/s0424820100143857.

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Over the past ten years several new ceramic materials have been developed for incorporation in high quality microwave integrated filters. A suitable ceramic dielectric microwave resonator material must have low loss in the microwave region, a low temperature coefficient of dielectric constant, and a high dielectric constant, typically 35-40. Most of the research conducted on the ceramic systems has focused upon phases in the BaO-TiO2 system. Many of the barium polytitanates have dielectric properties suited toward their use in microwave filters. Ba2Ti9O2O and BaTi4O9 are used commercially in the communications industry, and BaTi5O11 may also be a potential candidate for use in these systems.

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Hsu, Cheng Hsing, Chia Hao Chang, Wen Shiush Chen, Jenn Sen Lin, and Chun Hung Lai. "Effect of Sintering Behavior on Microwave Properties of (Ca_0.8Sr_0.2)ZrO₃ Ceramics for Resonators." Materials Science Forum 787 (April 2014): 338–41. http://dx.doi.org/10.4028/www.scientific.net/msf.787.338.

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Microwave dielectric properties and microstructures of (Ca0.8Sr0.2)ZrO3 ceramics prepared by the conventional solid-state route have been studied. The values of the dielectric constant (εr) were 22-26. The Q×f values of 10400–11500 GHz were obtained when the sintering temperatures were in the range of 1400–1490°C. The temperature coefficient of the resonant frequency τf was not sensitive to the sintering temperature. The εr value of 26, the Q×f value of 11500 GHz, and the τf value of-9 ppm/°C were obtained for (Ca0.8Sr0.2)ZrO3 ceramics sintering at 1490°C. The ceramic, (Ca0.8Sr0.2)ZrO3 is proposed as a suitable candidate material for application in highly selective microwave ceramic passive components.

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47

Bijumon, Pazhoor Varghese, and Mailadil Thomas Sebastian. "Temperature-stable microwave dielectric ceramics in the Ca5A2Ti1-xZrxO12 (A = Nb, Ta) system." Journal of Materials Research 19, no. 10 (October 1, 2004): 2922–28. http://dx.doi.org/10.1557/jmr.2004.0405.

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Ca5A2Ti1−xZrxO12 (A = Nb, Ta) ceramics were prepared through conventional solid-state ceramic route for 0 ⩽ x ⩽ 1. The crystal structures of the ceramics were studied by x-ray diffraction techniques, and dielectric properties were measured at microwave frequencies. In the Ca5Nb2Ti1−xZrxO12 system as x increases from 0 to 1, ϵr decreases from 48 to 25, Qu× f from 26,000 to 19,000 GHz, and τf from +40 to −21 ppm/°C. In Ca5Ta2Ti1−xZrxO12 ceramics, ϵr varies from 38 to 22, Quxf from 33,000 to 24,000 GHz, and τf from +10 to −26 ppm/°C as x is changed from 0 to 1. The variation of microwave dielectric properties with bond valence and electronegativity in the two systems were also investigated. Ca5Nb2Ti0.2Zr0.8O12 and Ca5Ta2Ti0.7Zr0.3O12 dielectric ceramics were found to have stable resonant frequency with temperature and are potential candidates for applications in personal and satellite communication systems in the S and C band (2–8 GHz).

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Ohsato, Hitoshi, Toshiyuki Ohhashi, Kazuhiko Sumiya, Shinya Suzuki, and Takashi Okuda. "Lattice Parameters of Bronze-Type 3BaO·2R2O3·9TiO2 (R=Sm and Nd) Solid Solutions for Microwave Dielectric Ceramics." Advances in X-ray Analysis 37 (1993): 79–85. http://dx.doi.org/10.1154/s0376030800015536.

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Microwave dielectric ceramics with high quality have received attention due to the rapid progress in microwave telecommunication and satellite broadcasting. The desirable properties in microwave dielectric resonators are a high dielectric constant (εr), low dielectric loss (tanδ) (i.e. high Q (Q =1/tanδ)), and low temperature coefficient of the resonant frequency(τf). Properties of dielectric ceramics in the TiO2-rich region of the BaO-Nd2O3-TiO2 ternary system (Fig. 1) were reported to have excellent dielectric constants, low dielectric losses and low temperature coefficients of capacitance by Kolar et al. (1978).

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Yao, Guo Guang, Hong Ma, and Xiu Lao Tian. "Synthesis and Microwave Dielectric Properties of Mg₅Nb₄TiO₁₇ Ceramics." Key Engineering Materials 538 (January 2013): 229–32. http://dx.doi.org/10.4028/www.scientific.net/kem.538.229.

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Mg5Nb4TiO17 ceramic was prepared by the conventional solid-state route for the first time and its microwave dielectric properties were investigated. The crystal structure and microstructure were analyzed using X-ray diffraction and scanning electron microscopy techniques. With increasing sintering temperature, the dielectric constant (εr) and quality factor (Q×f) increased firstly and then decreased, while the τf nearly unchanged. Mg5(NbTi)4O15-MgNb2O6 composite ceramics sintered at 1200 oC exhibits microwave dielectric properties of εr=15.1, Q×f=34,266.6 GHz (at 8.5GHz), τf=-63.8 ppm/oC.

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Nono, M. C. A., Pedro José Castro, E. G. L. Rangel, and S. L. Mineiro. "ZnO-Nb₂O₅-TiO₂ Dielectric Resonators and Porosity Influence on Dielectric Constant Values." Materials Science Forum 820 (June 2015): 193–98. http://dx.doi.org/10.4028/www.scientific.net/msf.820.193.

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The dielectric resonator (DR) is a ceramic component used in electronic circuits that can operate in microwave frequency range, where it plays the role of resonant element and enables the construction of high selective filters and oscillators. The dielectric properties of a ceramic resonator are influenced by their microstructure characteristics as pores amount. This work shows a study of the influence of pores amount (porosity) on the dielectric constant values of ceramics from ZnO-Nb2O5-TiO2 system. Mixtures of Nb2O5, ZnO, and TiO2 powders were compacted by uniaxial (100 MPa) and isostatic (300 MPa) pressing and sintered at 1100, 1200, and 1250°C. The experimental dielectric constant values of the sintered ceramics were corrected to eliminate the porosity influence. The results showed that the porosity, the type and quantities of crystalline chemical compounds in the ceramics influence the dielectric constant values.

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Journal articles on the topic 'Microwave dielectric ceramics'

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