Relevant bibliographies by topics / Pyrochlore

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Academic literature on the topic 'Pyrochlore'

Author: Grafiati
Published: 4 June 2021
Last updated: 25 May 2024

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Journal articles on the topic "Pyrochlore"

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Parshukova, K. N., E. P. Rylchenko, V. A. Muraviev, K. A. Badanina, B. A. Makeev, R. I. Korolev, and N. A. Zhuk. "SYNTHESIS OF MULTICOMPONENT COMPOUNDS WITH A PIROCHLORE-TYPE STRUCTURE." Steklo i Keramika, no. 10 (October 2022): 34–39. http://dx.doi.org/10.14489/glc.2022.10.pp.034-039.

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The possibility of solid-phase synthesis of multicomponent bismuth niobates and tantalates with pyrochlore-type structure (sp. gr. Fd-3m), containing atoms of transition 3d-elements in equimolar quantities is shown. The composition of this type pyrochlores can be described by stoichiometric formula Bi2Cr1/6Mn1/6Fe1/6Co1/6Ni1/6Cu1/6Ta(Nb)2O9 ± ?. A feature of synthesis of pyrochlores is a multi-stage high-temperature heat treatment process at a temperature of 650, 850, 950, 1050 °С for 60 hours. In the case of bismuth tantalate based pyrochlore, impurity phase of triclinic bismuth orthotantalate ?-BiTaO4 (sp. gr. P-1) is formed in trace amounts (? 8 mol.%). Complex pyrochlore based on bismuth niobate is characterized by a dense, low-porous microstructure in contrast to loose, porous tantalum pyrochlore with an average grain size of ? 2 µm. The unit cell parameter for pyrochlores containing niobium and tantalum is 10.4927(10.4922) ?, respectively.
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Rushton, M. J. D., Robin W. Grimes, C. R. Stanek, and Scott Owens. "Predicted pyrochlore to fluorite disorder temperature for A2Zr2O7 compositions." Journal of Materials Research 19, no. 6 (June 2004): 1603–4. http://dx.doi.org/10.1557/jmr.2004.0231.

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In a previous publication the order–disorder pyrochlore to fluorite transformation temperatures for a series of A2Hf2O7 pyrochlores were predicted [C.R. Stanek and R.W. Grimes: Prediction of rare-earth A2Hf2O7 pyrochlore phases. J. Am. Ceram. Soc. 2002, 85, p. 2139]. This was facilitated by establishing a relationship between these temperatures and the energy required to introduce a specific defect structure into the perfect pyrochlore lattice. Here an equivalent relationship for A2Zr2O7 pyrochlores was generated, and from this the disorder temperatures for a number of compositions including Eu2Zr2O7 were predicted.
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Mitchell, Roger H., Rudy Wahl, and Anthony Cohen. "Mineralogy and genesis of pyrochlore apatitite from The Good Hope Carbonatite, Ontario: A potential niobium deposit." Mineralogical Magazine 84, no. 1 (October 4, 2019): 81–91. http://dx.doi.org/10.1180/mgm.2019.64.

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AbstractThe Good Hope carbonatite is located adjacent to the Prairie Lake alkaline rock and carbonatite complex in northwestern Ontario. The occurrence is a heterolithic breccia consisting of diverse calcite, dolomite and ferrodolomite carbonatites containing clasts of magnesio-arfvedsonite + potassium feldspar, phlogopite + potassium feldspar together with pyrochlore-bearing apatitite clasts. The apatitite occurs as angular, boudinaged and schlieren clasts up to 5 cm in maximum dimensions. In these pyrochlore occurs principally as euhedral single crystals (0.1–1.5 cm) and can comprise up to 25 vol.% of the clasts. Individual clasts contain compositionally- and texturally-distinct suites of pyrochlore. The pyrochlores are hosted by small prismatic crystals of apatite (~100–500 μm × 10–25 μm) that are commonly flow-aligned and in some instances occur as folds. Allotriogranular cumulate textures are not evident in the apatitites. The fluorapatite does not exhibit compositional zonation under back-scattered electron spectroscopy, although ultraviolet and cathodoluminescence imagery shows distinct cores with thin (<50 μm) overgrowths. Apatite lacks fluid or solid inclusions of other minerals. The apatite is rich in Sr (7030–13,000 ppm) and rare earth elements and exhibits depletions in La, Ce, Pr and Nd (La/NdCN ratios (0.73–1.14) relative to apatite in cumulate apatitites (La/NdCN > 1.5) in the adjacent Prairie Lake complex. The pyrochlore are primarily Na–Ca pyrochlore of relatively uniform composition and minor Sr contents (<2 wt.% SrO). Irregular resorbed cores of some pyrochlores are A-site deficient (>50%) and enriched in Sr (6–10 wt.% SrO), BaO (0.5–3.5 wt.%), Ta2O5 (1–2 wt.%) and UO2 (0.5–2 wt.%). Many of the pyrochlores exhibit oscillatory zoning. Experimental data on the phase relationships of haplocarbonatite melts predicts the formation of apatite and pyrochlore as the initial liquidus phases in such systems. However, the texture of the clasts indicates that pyrochlore and apatite did not crystallise together and it is concluded that pyrochlores formed in one magma have been mechanically mixed with a different apatite-rich magma. Segregation of the apatite–pyrochlore assemblage followed by lithification resulted in the apatitites, which were disrupted and fragmented by subsequent batches of diverse carbonatites. The genesis of the pyrochlore apatitites is considered to be a process of magma mixing and not simple in situ crystallisation.
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Gunn, David S. D., John A. Purton, and Ilian T. Todorov. "Simulating Radiation-Induced Defect Formation in Pyrochlores." MRS Proceedings 1514 (2013): 15–20. http://dx.doi.org/10.1557/opl.2013.197.

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ABSTRACTThe accuracy and robustness of new Buckingham potentials for the pyrochlores Gd2Ti2O7 and Gd2Zr2O7 is demonstrated by calculating and comparing values for a selection of point defects with those calculated using a selection of other published potentials and our own ab inito values. Frenkel pair defect formation energies are substantially lowered in the presence of a small amount of local cation disorder. The activation energy for oxygen vacancy migration between adjacent O48f sites is calculated for Ti and Zr pyrochlores with the energy found to be lower for the non-defective Ti than for the Zr pyrochlore by ∼0.1 eV. The effect of local cation disorder on the VO48f → VO48f migration energy is minimal for Gd2Ti2O7, while the migration energy is lowered typically by ∼43 % for Gd2Zr2O7. As the healing mechanisms of these pyrochlores are likely to rely upon the availability of oxygen vacancies, the healing of a defective Zr pyrochlore is predicted to be faster than for the equivalent Ti pyrochlore.
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Livshits, Tatiana, Sergey Yudintsev, Sergey V. Stefanovsky, and Rodney Charles Ewing. "New Actinide Waste Forms with Pyrochlore and Garnet Structures." Advances in Science and Technology 73 (October 2010): 142–47. http://dx.doi.org/10.4028/www.scientific.net/ast.73.142.

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Cubic oxides with pyrochlore and garnet structures are promising matrices for long-lived actinides immobilization. Their isomorphic capacity with respect to An and REE was determined. To predict the long-term behavior of these matrices under their underground disposal radiation stability of synthetic pyrochlores and garnets was studied. Most of titanate phases have the critical (amorphization) doses close to 0.2 displacements per atom at 298 K. This value is significantly higher for Sn- and Zr-rich pyrochlores. Corrosion behavior of the pyrochlore- and garnet-composed matrices was investigated. The lowest actinides leach rates were observed in water and alkaline solutions most typical for underground waste repositories. Amorphization of the phases has a low influence on their corrosion behavior in solutions. Possibility for joint incorporation of actinides and Tc into zirconate- and titanate-based matrices with the pyrochlore structure is discussed.
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Khanvilkar, M. B., A. K. Nikumbh, S. M. Patange, R. A. Pawar, N. J. Karale, D. V. Nighot, P. A. Nagwade, M. D. Sangale, and G. S. Gugale. "Structural, electrical and magnetic properties of substituted pyrochlore oxide nanoparticles synthesized by the co-precipitation method." Physics and Chemistry of Solid State 22, no. 2 (June 16, 2021): 353–71. http://dx.doi.org/10.15330/pcss.22.2.353-371.

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Five substituted pyrochlore nanooxides such as Nd1.9Ho0.1Zr1.8Ce0.2O7, La1.95Ce0.05Zr0.29Ce1.71O7, Y1.79Pr0.21Ru1.99Pr0.01O7, Dy1.9Yb0.1Mn1.93Cu0.07O7 and Dy1.99Sr0.01Sn2O7 were synthesized by coprecipitation method. These precursors were monitored by thermal studies (TGA-DTA). The prepared nanosized substituted pyrochlore oxides were characterized by EDS, XRD, SEM, TEM, d. c. electrical conductivity, Thermoelectric power, Hall effect measurement, dielectric properties and magnetization measurements. XRD confirmed the formation of a single phase crystalline substituted pyrochlores with a cubic nature of nanoparticles. All substituted compounds were adopted a stable pyrochlore structure with rA3+/rB4+ = 1.395 except La1.95Ce0.05Zr0.29Ce1.71O7 compound, which has rA3+/rB4+ = 1.175 indicate disorder pyrochlore structure (i.e. fluorite structure). The temperature dependence of d. c. electrical conductivity for all substituted pyrochlores exhibits two distinct slopes with a break. This discontinuity can be attributed to extrinsic to intrinsic semiconducting properties. The thermoelectric power and Hall effect measurements for all compounds were confirmed the p-type semiconductivity except Y1.79Pr0.21Ru1.99Pr0.01O7 compound and which showed n-type semiconductivity. The dielectric constant (ε’) and dielectric loss (tan δ) i. e dissipation factor decreases with an increase in frequencies and reaching constant at particular frequencies. The applied field dependence of magnetization curve at room temperature (300 K) for Nd1.9Ho0.1Zr1.8Ce0.2O7, Y1.79Pr0.21Ru1.99Pr0.01O7 and Dy1.9Yb0.1Mn1.93Cu0.07O7, showed hysteresis loop with a small kink around the origin and which can be attributed to small but definite ferromagnetic ordering along with significant paramagnetic and superparamagnetic components. The magnetization at 2K showed a clear hysteresis loop for Dy1.9Yb0.1Mn1.93Cu0.07O7 and Dy1.99Sr0.01Sn2O7 pyrochlores are soft (weak) ferromagnets.
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Hase, I., Y. Higashi, and T. Yanagisawa. "Quasi-Flat-Band in s1/s2 Pyrochlore Oxides and the Effect of Spin-Orbit Interaction." Journal of Physics: Conference Series 2164, no. 1 (March 1, 2022): 012063. http://dx.doi.org/10.1088/1742-6596/2164/1/012063.

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Abstract An isotropic tight-binding model with the nearest-neighbour hopping on a pyrochlore lattice gives a rich variety of physical properties due to the emergence of the flat-band. Moreover, by introducing spin-orbit coupling into this model, the topological properties of the system changes significantly. This model is well applicable to some pyrochlore oxides called s1/s2 pyrochlores. In this paper we apply this model to an s2 pyrochlore oxide Pb2Ta2O7 and found a characteristic quadratic touching of the quasi-flat band and dispersive band. Furthermore, when a ferromagnetic order appears due to this quasi-flat band, a pair of Weyl points appears in that direction.
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Xue, Yuan, Ningyue Sun, and Guowu Li. "Evolution of Nb–Ta Oxide Minerals and Their Relationship to the Magmatic-Hydrothermal Processes of the Nb–Ta Mineralized Syenitic Dikes in the Panxi Region, SW China." Minerals 11, no. 11 (October 29, 2021): 1204. http://dx.doi.org/10.3390/min11111204.

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Previous geochemical and petrological studies have concluded that initially magmatic Nb–Ta mineralization is often modified by post-magmatic hydrothermal fluids; however, there is still a lack of mineralogical evidence for the syenite-related Nb–Ta deposit. From the perspective of Nb–Ta minerals, the pyrochlore supergroup minerals have significance for indicating the fluid evolution of alkaline rock or related carbonatite type Nb–Ta deposits. The Panzhihua–Xichang (Panxi) region is a famous polymetallic metallogenic belt in southwestern China, abound with a huge amount of Nb–Ta mineralized syenitic dikes. This study focuses on the mineral textures and chemical compositions of the main Nb–Ta oxide minerals (including columbite-(Fe), fersmite, fergusonite-(Y), and especially pyrochlore group minerals) in samples from the Baicao and Xiaoheiqing deposits, in the Huili area, Panxi region, to reveal the magma evolution process of syenitic-dike-related Nb–Ta deposits. The Nb–Ta oxides in the Huili syenites are commonly characterized by a specific two-stage texture on the crystal scale, exhibiting a complex metasomatic structure and compositional zoning. Four types of pyrochlore group minerals (pyrochlores I, II, III, and IV) formed in different stages were identified. The euhedral columbite-(Fe), fersmite, and pyrochlores I and II minerals formed in the magmatic fractional crystallization stage. Anhedral pyrochlore III minerals are linked to the activity of magma-derived hydrothermal fluids at the late stages of magma evolution. The pyrochlore IV minerals and fergusonite-(Y) tend to be more concentrated in areas that have undergone strong albitization, which is a typical phenomenon of hydrothermal alteration. These mineralogical phenomena provide strong evidences that the magmatic-hydrothermal transitional stage is the favored model for explaining the Nb–Ta mineralization process. It is also concluded that the changes in chemical composition and texture characteristics for pyrochlore group minerals could serve as a proxy for syenite-related Nb–Ta mineralization processes.
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Wang, Yuhao, Chong Jing, Zhao-Ying Ding, Yun-Zhuo Zhang, Tao Wei, Jia-Hu Ouyang, Zhan-Guo Liu, Yu-Jin Wang, and Ya-Ming Wang. "The Structure, Property, and Ion Irradiation Effects of Pyrochlores: A Comprehensive Review." Crystals 13, no. 1 (January 13, 2023): 143. http://dx.doi.org/10.3390/cryst13010143.

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Since the beginning of the use of nuclear energy, humans have been faced with the problem of radionuclide disposal. At present, a large amount of waste is stored in pools or dry tanks at reactor sites. With the development of the nuclear power generation industry worldwide, the high storage cost (including building, maintaining, and operating storage pools) is overwhelming and serious, and urgent radionuclide disposal problems have become increasingly difficult. Safe and economical strategies are urgently needed for long-term storage and disposal of nuclear waste, which has become among the core issues in the utilization of nuclear energy. Pyrochlore ceramics are able to immobilize a variety of radionuclides and have excellent irradiation stability, so they have received extensive attention as hosts of radionuclides waste. This review summarizes the structure, composition, synthesis process, properties, and irradiation stability of pyrochlore ceramics, focusing on the ion irradiation effect of pyrochlore. In general, the cation radii ratio rA/rB is a key parameter related to various properties of pyrochlores. Zirconate pyrochlore is more easily transformed from pyrochlore to defective fluorite, and leads to better irradiation resistance.
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Talanov, Mikhail V., and Valeriy M. Talanov. "Formation of breathing pyrochlore lattices: structural, thermodynamic and crystal chemical aspects." CrystEngComm 22, no. 7 (2020): 1176–87. http://dx.doi.org/10.1039/c9ce01635j.

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Dissertations / Theses on the topic "Pyrochlore"

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Disseler, Steven Michael Thomas. "Magnetic Order in the Pyrochlore Iridates." Thesis, Boston College, 2013. http://hdl.handle.net/2345/3148.

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Thesis advisor: Michael J. Graf
This thesis is concerned with experimentally determining the magnetic and electronic states in a unique class of transition metal oxides known as the pyrochlore iridates, A₂Ir₂O₇ (A = Y or Rare earth). The extended nature of the 5d Ir orbitals in the iridates places these materials in a regime of intermediate electron correlation and large spin-orbit interaction such that this system may host several novel or topological states of matter which may be perturbed by incorporating different A-species. Additionally, the pyrochlore structure is geometrically frustrated and has been long been studied as a potential host of a number of exotic magnetic phenomenon. However, even after years of intense theoretical and experimental interest many fundamental questions still remain about the nature of the magnetic ground sates in this series which are of vital importance in understanding the roles of various interactions and potential of such novel phenomenon. The primary aim of this thesis is therefore to determine how magnetic order develops on the Ir sublattice in this series, particularly how it is perturbed through variation of the crystalline structure, magnetism of the A-site ions, and presence of mobile charges. This thesis is the first comprehensive experimental study of these effects which has utilized several complementary experimental probes of both bulk and local magnetism in a number of compounds. The techniques presented in this work include magnetotransport, bulk magnetization, elastic neutron scattering, and muon spin relaxation (µSR) measurements. All of the three compounds studied in this work (A = Y, Yb, and Nd) are shown to definitively exhibit long-range magnetic order on the Ir sublattice, which has previously only been inferred based on studies of other compounds. The compounds Y₂Ir₂O₇ and Yb₂Ir₂O₇ are correlated insulators at low temperature and are found to have identical configuration of the Ir moments, despite the presence of the large localized Yb³⁺. Numerical investigations presented here have provided the first conclusive evidence that this order is of the `all-in/all-out' type, consistent with recent resonant x-ray studies; additionally, we have shown that this order exists for all insulating compounds regardless of structural parameters or properties of the A-ion. On the other hand, Nd₂Ir₂O₇ is weakly metallic with Kondo-like behavior at low temperature, with long-range order only on the Ir site, in disagreement with previous results from neutron scattering. Measurements of the field dependent magnetization and Hall effect reveal a large anomalous Hall component, suggesting that the Nd3+ may exhibit a spin-ice state with very short correlation length, while the Ir sublattice is likely in the `all-in/all-out' state. From this, it is determined that Nd₂Ir₂O₇ lies at an important cross-over point in the series in which correlation energy and conduction bandwidth yield chiral order with features akin to both the metallic unordered Pr₂Ir₂O₇ and those of the magnetically ordered insulators. These results are discussed with regard to recent theoretical models exploring the role of electron correlation, frustration and various exchange interactions in these materials
Thesis (PhD) — Boston College, 2013
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Physics
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Wilde, Peter Joseph. "The defect chemistry of pyrochlore structured oxides." Thesis, University College London (University of London), 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309471.

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Mostaed, Ali. "Atomic structure study of pyrochlore ytterbium titanate." Thesis, University of Warwick, 2017. http://wrap.warwick.ac.uk/96357/.

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There has been great interest in the magnetic behaviour of pyrochlore oxides with the general formula A2B2O7, in which rare-earth (A), and transition metal (B) cations are ordered on separate interpenetrating lattices of corner-sharing tetrahedra. Such materials exhibit behaviours including quantum spin-ice, (quantum) spin-liquid, and ordered magnetic ground states. Yb2Ti2O7 lies on the boundary between a number of competing magnetic ground states. Features in the low-temperature specific heat capacity that vary in sharpness and temperature from sample to sample suggest that in some cases the magnetic moments order, while in others the moments remain dynamic down to temperatures as low as ~16 mK. In this work, three different Yb2Ti2O7 single crystal samples, all grown by the optical floating zone technique but exhibiting quite different heat capacity behaviour, are studied by aberration-corrected scanning transmission microscopy (STEM). Atomic-scale energy-dispersive X-ray (EDX) analysis shows that a crystal with no specific heat anomaly has substitution of Yb atoms on Ti sites (“stuffing"). In fact, EDX analysis shows for the first time that “stuffing” of Yb (A) cations onto Ti (B) sites in the lattice can be observed directly in the pyrochlore structure. Moreover, I show that the detailed intensity distribution around the visible atom columns in annular dark field STEM images is sensitive to the presence of nearby atoms of low atomic number (in this case oxygen) and find significant differences between the samples that correlates both with their magnetic behaviour and measurements of Ti oxidation state using electron energy loss spectroscopy. These measurements support the view that the magnetic ground state of Yb2Ti2O7 is extremely sensitive to disorder. On the other hand, structural modification of ytterbium titanate by deviation from stoichiometry as well as electron irradiation is studied in this work. I show that Ti excess is accommodated by Yb cation vacancies while Yb excess is compensated by Yb interstitials. Furthermore, two MATLAB programs, Detect Columns and BurgersVectors, to analyse STEM images and calculate the dislocation density tensor of STEM images as well as their Burgers vector(s) are respectively introduced in this work.
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Simon, Charles Francis. "The synthesis and characterisation of pyrochlore frameworks." Thesis, University of Southampton, 2010. https://eprints.soton.ac.uk/203757/.

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Structural studies have been undertaken on a wide range of pyrochlore phases, with a focus on garnering a better understanding of the factors determining the formation and behavior of these materials. Extensive structural characterisation has been undertaken primarily using powder X-ray and powder neutron diffraction techniques to explore the subtle structural changes that occur as a result of changes in composition on the two interlocking networks that make up the pyrochlore structure. Particular attention has been paid to hydrated beta-pyrochlore materials, using high resolution TOF and constant wavelength PND to accurately determine the location and orientation of the water molecules within the structure. The location of these molecules has been shown to be directly correlated to the overall lattice dimensions of the pyrochlore framework, with the subsequent molecular orientation and internal bond angles changing to provide an optimum stabilization effect on the A-site cation. Investigation into the effects of hydration upon the superconducting beta-pyrochlore series AOs2O6.nH2O (where A = K, Rb and Cs) has also been investigated; with a correlation between the structural changes, the degree of hydration and the onset of the superconducting state being discussed. Also presented is work seeking to determine the scope and effects of ion-exchange on the A2O’ network of the pyrochlore framework, with several new phases synthesised and other known phases extensively characterized along with a discussion regarding the limits of what may be included in the pyrochlore framework.
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Champion, John Dickon Mathison. "Theoretical and experimental investigations of frustrated pyrochlore magnets." Thesis, University College London (University of London), 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249647.

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Eberman, Kevin W. (Kevin Wilmot) 1971. "Crystallographic origins of fast-ion conduction in pyrochlore." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/50456.

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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1998.
Includes bibliographical references (p. 129-132).
We have examined the crystallographic origins of fast-ion conduction in oxides with the pyrochlore structure-type, ideally A2B2O7, a superstructure of (A,B)20 3.5 defect fluorite-like array. These materials have technological promise for use in electrochemical devices such as oxygen sensors and solid-oxide fuel-cells. The pathway for ion conduction proposed by several authors has been a jump between equivalent nearest-neighbor oxygen sites through the tetrahedral edges of the relatively-immobile cation array. Substitution of a third cation species in slid-solution in the B site, A2(B-yB'y)2O7, results in a marked change in the structure and properties of the materials which is not fully understood. As the average radius of the cations occupying the B-site increases (with changing composition) towards that of the larger average radius of the cations occupying the Asite, a tendency for increasing disorder has been observed, where complete disorder corresponds to the fluorite structure. A decrease in Frenkel-defect formation-energy and an increase in the migration enthalpy accompanies the disordering. We have executed several studies of pyrochlore structures employing neutron and x-ray powder diffraction. In particular, we have focused on high-temperature in-situ experiments that should better correspond to the structure for which the conductivity measurements were made at elevated temperature ...
by Kevin W. Eberman.
Ph.D.
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Pirzada, Mohsin Tanveer-Ul-Haq Farouqi. "Atomic scale computer simulations of pyrochlore and spinel oxides." Thesis, Imperial College London, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.406556.

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Galati, Rosa. "Synthesis, structure and properties of heavy metal pyrochlore oxides." Thesis, University of Southampton, 2010. https://eprints.soton.ac.uk/173963/.

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Many interesting and often exotic magnetic phenomena have been observed over the past twenty years in the family of the heavy metal pyrochlore oxides, A2B2O6O’. In these systems, competing interactions are common and tend to emerge mainly at low temperatures. Magnetic properties are related to the contribution of d orbitals that transition metal (TM) offer and their interplay with the positive contribution coming from the cation sitting on the A site. The work described in this thesis explores the effects of chemical substitution of the A site cation on the symmetry and the properties of a number of pyrochlores containing TM of the second and third transition row, such as Ir, Ru, Mo and Os. Depending if this site is fully occupied and on the radius size the behaviour of the resulting material can change significantly. The defect pyrochlore family AOs2O6 (A = Cs, Rb, K) was studied in detail following the attention that its members attracted for having been the first materials, belonging to this subgroup, to exhibit superconducting properties [1, 2, 3] and for the diversity in their properties. In these compounds, the smaller the ionic radius of an element, the weaker is the bond to the structure. As a result, the temperature dependence of their energy becomes quite different from normal lattice vibrations and gives interesting low temperature behaviours. The effect of replacing the weak bonded potassium ions on the structures and superconducting properties of the AOs2O6 phases has also been studied. The ability to exchange the A-type in pyrochlores is well known and leads to applications for example in nuclear clean-up. Thus the ion exchange of K+ by smaller cations such as Li+ or Na+ has been investigated with the aim of synthesising compounds which cannot be obtained by direct synthesis. New defect pyrochlore materials, AA’Os2O6 (A’ = Li+, Na+) have been synthesised together with hydrated derivatives, AA’OsO6.nH2O. Parent materials were obtained by ion exchange in non-aqueous solvents under strictly dry conditions. A Ba-based osmium oxide pyrochlore, Ba(Os2O6)2.H2O was also synthesised, for the first time, from the K-osmate starting material by ion-exchange methods in aqueous medium. In this work, diffraction techniques, X- ray and neutron powder diffraction, were employed and found suitable for detecting the change in cation and anion location and general structure investigation.These structural descriptions are correlated with the measured superconducting properties and theoretical descriptions of variations in the Tc in these systems as a function of cation size and rattling.
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Porter, Spencer H. "Perovskite and Pyrochlore Tantalum Oxide Nitrides: Synthesis and Characterization." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1332499280.

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Benton, John Owen. "Classical and quantum spin liquids on the pyrochlore lattice." Thesis, University of Bristol, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.681486.

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The study of frustrated magnetism sits at the frontier of modern condensed matter physics, offering the possibility to discover new states of matter with exotic excitations. A textbook example of this is seen in the rare earth pyrochlore oxides H02Ti20 7 and DY2Ti207, better known as "spin ice". These magnets exhibit a classical spin liquid state with emergent magnetic monopole excitations. Inspired by this, we explore in this thesis a wide landscape of possibilities for novel magnetic behaviour on the pyrochlore lattice. Starting from the most general model for anisotropic nearest neighbour exchange interactions we show that the full zero temperature classical phase diagram can be obtained simply by considering the symmetries of a tetralledron. In the process of doing this we obtain an exact rewriting of the model in terms of a set of local order parameter fields defined on tetrahedra. After classifying and describing the ordered phases of this model we turn to give consideration to the novel physics which may be found near the boundaries where phases with different symmetry meet. We find that interesting properties of several materials can be traced back to the "accidental" degeneracies which arise on these boundaries. These include the "order by disorder" in Er2Ti207, the "dimensional-reduction" observed in Yb2Ti207, and the suppression of The observation that the physics of the phase boundaries manifests itself throughout the nearby regions of the phase diagram leads us to a systematic analysis of all of the phase boundaries of the model. In several cases dipole order persists at the phase boundary, stabilised by fluctuations. By constructing the ground state manifolds in each case we identify those configurations which are favoured by fluctuations. We also identify two limits of the phase diagram in which dipolar order vanishes to be replaced by spin nematic order. At certain phase boundaries we find that magnetic order vanishes entirely. This leads to the discovery of a new classical spin liquid on the pyrochlore lattice- the anisotropic Coulomb liquid. This spin liquid, like the Coulomb phase observed in spin ice, possesses algebraic correlations and conserved fluxes but also presents several new features including an anisotropic Coulomb interaction between its excitations. A long-wavelength theory of this spin liquid is derived from the microscopic model by coarse graining the fluctuations of the local order-parameter fields. Homing in on a different limit of the phase diagram, we move on to consider the effects of quantum fluctuations on a spin ice material and in particular how these effects would manifest themselves in neutron scattering experiments. We explore the correlations of the U(I) spin liquid which arises in this limit by explicitly constructing a basis of photon operators on the pyrochlore lattice and calculating the associated dispersion relation and correlation functions. This enables us to quantitatively describe how these unusual excitations would manifest themselves in neutron scattering experiments. We find that "pinch points," which are the signal feature of a classical spin ice, fade away as a quantum ice is cooled to its quantum spin liquid ground state.
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Books on the topic "Pyrochlore"

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Fukina, Diana G., Artem S. Belousov, and Evgeny V. Suleimanov, eds. Pyrochlore Oxides. Cham: Springer Nature Switzerland, 2024. http://dx.doi.org/10.1007/978-3-031-46764-6.

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Wang, Runzhi. Many-body theory of pyrochlore iridates and related materials. [New York, N.Y.?]: [publisher not identified], 2018.

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Pyrochlore Ceramics. Elsevier, 2022. http://dx.doi.org/10.1016/c2020-0-03299-8.

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Night, Starla. Onyx Dragons: Pyrochlore. XQS, 2018.

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Pyrochlore Ceramics: Properties, Processing, and Applications. Elsevier, 2022.

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Chowdury, Anirban. Pyrochlore Ceramics: Properties, Processing, and Applications. Elsevier, 2022.

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Thorogood, Gordon James, Sarah C. Finkeldei, Maik Kurt Lang, and David Simeone, eds. Ordered and Disordered Cubic Systems: Pyrochlore to Fluorite, Now and the Horizon. Frontiers Media SA, 2022. http://dx.doi.org/10.3389/978-2-88974-425-1.

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Beckett, Martyn Frank. Phase relations in synthetic alkali-bearing dolomite carbonatites and the effect of alkalinity and fluorine content on the solubility of pyrochlore and the formation of nobium deposits in carbonatites. 1987.

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Book chapters on the topic "Pyrochlore"

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Gordon, R. S. "Perovskite and Pyrochlore Oxides." In Inorganic Reactions and Methods, 218–19. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2007. http://dx.doi.org/10.1002/9780470145333.ch151.

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Castroviejo, Ricardo. "Pyrochlore (pyc/koppite, columbomicrolite)." In A Practical Guide to Ore Microscopy—Volume 1, 603–6. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-12654-3_100.

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Gaulin, Bruce D., and Jason S. Gardner. "Experimental Studies of Pyrochlore Antiferromagnets." In Introduction to Frustrated Magnetism, 177–206. Berlin, Heidelberg: Springer Berlin Heidelberg, 2010. http://dx.doi.org/10.1007/978-3-642-10589-0_8.

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Prabhakaran, D. "Crystal Growth of Pyrochlore Compounds." In Springer Series in Solid-State Sciences, 19–35. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-70860-3_2.

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Fukina, D. G., and E. V. Suleimanov. "Structural Type of α-Pyrochlore Oxides." In Green Chemistry and Sustainable Technology, 1–36. Cham: Springer Nature Switzerland, 2023. http://dx.doi.org/10.1007/978-3-031-46764-6_1.

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Matsuhira, K., and S. Nakatsuji. "Anomalous Transport Properties of Pyrochlore Iridates." In Springer Series in Solid-State Sciences, 399–418. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-70860-3_14.

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Azarnova, Liudmila. "Bolshetagninskoe Deposit Microcline–Pyrochlore Ore Process Mineralogy." In Springer Geochemistry/Mineralogy, 223–32. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-13948-7_23.

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Ishizuka, Hiroaki. "Spin-Cluster State in a Pyrochlore Lattice." In Magnetism and Transport Phenomena in Spin-Charge Coupled Systems on Frustrated Lattices, 103–14. Tokyo: Springer Japan, 2015. http://dx.doi.org/10.1007/978-4-431-55663-3_8.

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Wang, Honglong, Emily Tarwater, Xinxing Zhang, Xinxing Zhang, Zhizhi Sheng, and Jeffrey W. Fergus. "Pyrochlore Lanthanide Zirconates for Thermal Barrier Coatings." In Processing and Properties of Advanced Ceramics and Composites VII, 417–24. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2015. http://dx.doi.org/10.1002/9781119183860.ch39.

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Fukina, D. G., and E. V. Suleimanov. "Structural Type of β-Pyrochlore Oxides AM2O6." In Green Chemistry and Sustainable Technology, 37–59. Cham: Springer Nature Switzerland, 2023. http://dx.doi.org/10.1007/978-3-031-46764-6_2.

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Conference papers on the topic "Pyrochlore"

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Tucker, David, Ayyakkannu Manivannan, Dan Haynes, Harry Abernathy, Nick Miller, Karon Wynne, and Angine´s Matos. "Evaluating Methods for Infiltration of LSCF Cathodes With Mixed Electric/Ionic Conductors for Improved Oxygen Exchange." In ASME 2010 8th International Conference on Fuel Cell Science, Engineering and Technology. ASMEDC, 2010. http://dx.doi.org/10.1115/fuelcell2010-33214.

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Infiltration methods for improving lanthanum strontium cobalt ferrite (LSCF) cathode performance through catalyst surface modification were evaluated at the U.S. Department of Energy, National Energy Technology Laboratory. Infiltration of mixed conductors into LSCF cathodes of solid oxide fuel cells promises a low cost method of improving oxygen exchange and performance in these materials at lower temperatures. LSCF cathodes on Nickel-Yttria Stabilized Zirconia (Ni-YSZ) anode supported cells were infiltrated with strontium-doped lanthanum zirconate (LSZ) pyrochlores using two methods. An aqueous solution of nitrate salts was vacuum infiltrated into the cathodes of anode supported button cells, and the cells were heated to form the pyrochlore phase in-situ. This was compared to the efficacy of infiltrating a suspension of pyrochlore nanoparticles. Different dispersants were used to prepare the nanoparticle suspensions at varying concentrations and pH levels, and the results are compared.
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Xu, Huifang. "Microstructure and Composition of a Ce-pyrochlore: A Chemical Analog for Pu-pyrochlore." In PLUTONIUM FUTURES - THE SCIENCE: Third Topical Conference on Plutonium and Actinides. AIP, 2003. http://dx.doi.org/10.1063/1.1594615.

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Wang, S. X. "Radiation resistance of gadolinium zirconate pyrochlore." In Plutonium futures-The science (Topical conference on Plutonium and actinides). AIP, 2000. http://dx.doi.org/10.1063/1.1292183.

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Lian, J., R. C. Ewing, S. V. Yudintsev, and S. V. Stefanovsky. "Radiation Stability of Melted Titanate Waste Forms for Actinide Immobilization." In ASME 2001 8th International Conference on Radioactive Waste Management and Environmental Remediation. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/icem2001-1316.

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Abstract Radiation stability of titanate ceramics suggested for actinide-bearing waste immobilization was studied. The major actinide (uranium) hosts in the samples prepared by melting followed by crystallization in a resistive furnace and in a cold crucible are phases with fluorite-related structure (zirconolite, pyrochlore, murataite) as well as brannerite. Critical amorphization doses at room temperature for these phases irradiated with 1 MeV Kr+ ions were (× 1018 ions/m2) ∼3, 1.8–2.4, 1.7–1.9, and 1.4 for zirconolite, pyrochlore, murataite, and brannerite, respectively. Murataite varieties with three-, five-, and eight-fold fluorite cells have the similar radiation stability. Recalculation of critical amorphization dose to dpa estimates a time required for murataite amorphization as 600–700 years at 10 wt.% 239Pu content. Similar values have been established previously for pyrochlore-structured titanates proposed for plutonium immobilization (because there will be also some commercial Pu issue).
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Kumar, Harish, and A. K. Pramanik. "Glass-like behavior in pyrochlore iridate Y2Ir2O7." In DAE SOLID STATE PHYSICS SYMPOSIUM 2015. Author(s), 2016. http://dx.doi.org/10.1063/1.4948159.

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Reece, Margaret, Xiaodong Zhao, Jiahong Li, Xiaofeng Guo, Juejing Liu, Jaun Wen, Di Wu, Xianghui Zhang, and Qiang Zhang. "Surface thermodynamics of yttrium titanate pyrochlore materials." In Goldschmidt2022. France: European Association of Geochemistry, 2022. http://dx.doi.org/10.46427/gold2022.8987.

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Bala, Indu, M. Roy, S. K. Barbar, and S. Sahu. "Structural and dielectric properties of Bi2Sn2-xTixO7 pyrochlore." In SOLID STATE PHYSICS: Proceedings of the 56th DAE Solid State Physics Symposium 2011. AIP, 2012. http://dx.doi.org/10.1063/1.4710341.

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Mohapatra, M., B. Rajeswari, N. S. Hon, R. M. Kadam, and V. Natarajan. "Speciation of uranium in La2Zr2O7 pyrochlore by TRPLS." In NANOFORUM 2014. AIP Publishing LLC, 2015. http://dx.doi.org/10.1063/1.4917981.

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Abdullah, Asiah, Nurul Hidayah Aslam, Sheikh Ahmad Izaddin Sheikh Mohd Ghazali, Nurazira Mohd Nor, Nur Nadia Dzulkifli, Nazrizawati Ahmad Tajuddin, Arif Hidayat, and Is Fatimah. "Synthesis and characterization of Bismuth copper tantalate pyrochlore." In 5TH INTERNATIONAL CONFERENCE ON ELECTRICAL, ELECTRONIC, COMMUNICATION AND CONTROL ENGINEERING (ICEECC 2021). AIP Publishing, 2023. http://dx.doi.org/10.1063/5.0136917.

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Narumi, Yasuo, Akiko Kikkawa, Koichi Katsumata, Zentaro Honda, Masayuki Hagiwara, and Koichi Kindo. "High-Field Magnetization of the Pyrochlore Compound Gd2Ti2O7." In LOW TEMPERATURE PHYSICS: 24th International Conference on Low Temperature Physics - LT24. AIP, 2006. http://dx.doi.org/10.1063/1.2355092.

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Reports on the topic "Pyrochlore"

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Tuller, H. L. Structural disorder and transport in ternary oxides with the pyrochlore structure. Office of Scientific and Technical Information (OSTI), January 1989. http://dx.doi.org/10.2172/6237884.

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Desbarats, A. J., and J. B. Percival. Hydrogeochemistry of mine tailings from a carbonatite-hosted Nb-REE deposit, Oka, Quebec, Canada. Natural Resources Canada/CMSS/Information Management, 2023. http://dx.doi.org/10.4095/331256.

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Environmental impacts associated with the mining of carbonatite deposits are an emerging concern due to the demand for critical metals. This study investigates the chemistry of tailings seepage at the former Saint Lawrence Columbium mine near Oka, Québec, Canada, which produced pyrochlore concentrate and ferroniobium from a carbonatite-hosted Nb-REE deposit. Its objectives are to characterize the mineralogy of the tailings and their pore water and effluent chemistries. Geochemical mass balance modeling, constrained by aqueous speciation modeling and mineralogy, is then used to identify reactions controlling the chemical evolution of pore water along its flow path through the tailings impoundment. The tailings are composed mainly of REE-enriched calcite (82 wt. %), biotite (12 wt. %) and fluorapatite (4 wt. %). Minor minerals include chlorite, pyrite, sphalerite, molybdenite and unrecovered pyrochlore. Secondary minerals include gypsum, barite and strontianite. Within the unsaturated zone, pore water chemistry is controlled by sulfide oxidation and calcite dissolution with acid neutralization. With increasing depth below the water table, pore water composition reflects gypsum dissolution followed by sulfate reduction and FeS precipitation driven by the oxidation of organic carbon in the tailings. Concomitantly, incongruent dissolution of biotite and chlorite releases K, Mg, Fe, Mn, Ba and F, forming kaolinite and Ca-smectite. Cation exchange reactions further remove Ca from solution, increasing concentrations of Na and K. Fluoride concentrations reach 23 mg/L and 8 mg/L in tailings pore water and effluent, respectively. At a pH of 8.3, Mo is highly mobile and reaches an average concentration of 83 µg/L in tailings effluent. Although U also forms mobile complexes, concentrations do not exceed 16 µg/L due to the low solubility of its pyrochlore host. Adsorption and the low solubility of pyrochlore limit concentrations of Nb to less than 49 µg/L. Cerium, from calcite dissolution, is strongly adsorbed although it reaches concentrations (unfiltered) in excess of 1 mg/L and 100 µg/L in pore water and effluent, respectively. Mine tailings from carbonatite deposits are enriched in a variety of incompatible elements with mineral hosts of varying reactivity. Some of these elements, such as F and Mo, may represent contaminants of concern because of their mobility in alkaline tailings waters.
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Lumpkin, G. R., R. C. Ewing, and E. M. Foltyn. Thermal recrystallization of alpha-recoil damaged minerals of the pyrochlore structure type. Office of Scientific and Technical Information (OSTI), October 1985. http://dx.doi.org/10.2172/437684.

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Tuller, Harry L. Structural disorder and transport in ternary oxides with the pyrochlore structure. Final report. Office of Scientific and Technical Information (OSTI), June 2001. http://dx.doi.org/10.2172/771370.

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Ismail, Ahmed E., Stephen Martin Foiles, Jeffery A. Greathouse, and Paul Stewart Crozier. The effect of electron-ion coupling on radiation damage simulations of a pyrochlore waste form. Office of Scientific and Technical Information (OSTI), November 2009. http://dx.doi.org/10.2172/974414.

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Ryerson, F. J., B. Ebbinghaus, O. Kirkorian, and R. VanKonynenburg. Saturation of impurity-rich phases in a cerium-substituted pyrochlore-rich titanate ceramic: part 1 experimental results. Office of Scientific and Technical Information (OSTI), May 2000. http://dx.doi.org/10.2172/15005706.

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Ryerson, F. J., and B. Ebbinghaus. Pyrochlore-rich titanate ceramics for the immobilization of plutonium: redox effects on phase equilibria in cerium- and thorium- substituted analogs. Office of Scientific and Technical Information (OSTI), May 2000. http://dx.doi.org/10.2172/15005705.

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