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Clemens Ritter - One of the best experts on this subject based on the ideXlab platform.
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A quantum liquid of magnetic octupoles on the Pyrochlore lattice
Nature Physics, 2020Co-Authors: Romain Sibille, Nicolas Gauthier, Elsa Lhotel, Victor Porée, Vladimir Pomjakushin, Russell A. Ewings, Toby G. Perring, Jacques Ollivier, Andrew Wildes, Clemens RitterAbstract:A detailed neutron-scattering study reveals a quantum spin liquid behaviour in Ce_2Sn_2O_7 originating from its higher-order magnetic multipolar moments acting on the geometrically frustrated Pyrochlore lattice. Spin liquids are highly correlated yet disordered states formed by the entanglement of magnetic dipoles^ 1 . Theories define such states using gauge fields and deconfined quasiparticle excitations that emerge from a local constraint governing the ground state of a frustrated magnet. For example, the ‘2-in–2-out’ ice rule for dipole moments on a tetrahedron can lead to a quantum spin ice^ 2 – 4 in rare-earth Pyrochlores. However, f -electron ions often carry multipole degrees of freedom of higher rank than dipoles, leading to intriguing behaviours and ‘hidden’ orders^ 5 , 6 . Here we show that the correlated ground state of a Ce^3+-based Pyrochlore, Ce_2Sn_2O_7, is a quantum liquid of magnetic octupoles. Our neutron scattering results are consistent with a fluid-like state where degrees of freedom have a more complex magnetization density than that of magnetic dipoles. The nature and strength of the octupole–octupole couplings, together with the existence of a continuum of excitations attributed to spinons, provides further evidence for a quantum ice of octupoles governed by a ‘2-plus–2-minus’ rule^ 7 , 8 . Our work identifies Ce_2Sn_2O_7 as a unique example of frustrated multipoles forming a ‘hidden’ topological order, thus generalizing observations on quantum spin liquids to multipolar phases that can support novel types of emergent fields and excitations.
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a quantum liquid of magnetic octupoles on the Pyrochlore lattice
arXiv: Strongly Correlated Electrons, 2019Co-Authors: Romain Sibille, Nicolas Gauthier, Elsa Lhotel, Victor Porée, Vladimir Pomjakushin, Russell A. Ewings, Toby G. Perring, Jacques Ollivier, Andrew Wildes, Clemens RitterAbstract:Spin liquids are highly correlated yet disordered states formed by the entanglement of magnetic dipoles$^1$. Theories typically define such states using gauge fields and deconfined quasiparticle excitations that emerge from a simple rule governing the local ground state of a frustrated magnet. For example, the '2-in-2-out' ice rule for dipole moments on a tetrahedron can lead to a quantum spin ice in rare-earth Pyrochlores - a state described by a lattice gauge theory of quantum electrodynamics$^{2-4}$. However, f-electron ions often carry multipole degrees of freedom of higher rank than dipoles, leading to intriguing behaviours and 'hidden' orders$^{5-6}$. Here we show that the correlated ground state of a Ce$^{3+}$-based Pyrochlore, Ce$_2$Sn$_2$O$_7$, is a quantum liquid of magnetic octupoles. Our neutron scattering results are consistent with the formation of a fluid-like state of matter, but the intensity distribution is weighted to larger scattering vectors, which indicates that the correlated degrees of freedom have a more complex magnetization density than that typical of magnetic dipoles in a spin liquid. The temperature evolution of the bulk properties in the correlated regime below 1 Kelvin is well reproduced using a model of dipole-octupole doublets on a Pyrochlore lattice$^{7-8}$. The nature and strength of the octupole-octupole couplings, together with the existence of a continuum of excitations attributed to spinons, provides further evidence for a quantum ice of octupoles governed by a '2-plus-2-minus' rule. Our work identifies Ce$_2$Sn$_2$O$_7$ as a unique example of a material where frustrated multipoles form a 'hidden' topological order, thus generalizing observations on quantum spin liquids to multipolar phases that can support novel types of emergent fields and excitations.
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oxygen miscibility gap and spin glass formation in the Pyrochlore lu2mo2o7
Journal of Solid State Chemistry, 2013Co-Authors: Lucy Clark, Clemens Ritter, A Harrison, J. Paul AttfieldAbstract:Abstract Rare earth ( R ) molybdate Pyrochlores, R 2 Mo 2 O 7 , are of interest as frustrated magnets. Polycrystalline samples of Lu 2 Mo 2 O 7− x prepared at 1600 °C display a coexistence of cubic Pyrochlore phases. Rietveld fits to powder neutron diffraction data and chemical analyses show that the miscibility gap is between a stoichiometric x =0 and an oxygen-deficient x ≈0.4 phase. Lu 2 Mo 2 O 7 behaves as a spin glass material, with a divergence of field cooled and zero field cooled DC magnetic susceptibilities at a spin freezing temperature T f =16 K, that varies with frequency in AC measurements following a Vogel–Fulcher law. Lu 2 Mo 2 O 6.6 is more highly frustrated spin glass and has T f =20 K.
Rodney C. Ewing - One of the best experts on this subject based on the ideXlab platform.
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similar local order in disordered fluorite and aperiodic Pyrochlore structures
Acta Materialia, 2018Co-Authors: Jacob Shamblin, Rodney C. Ewing, Mikhail Feygenson, Christina Trautmann, Cameron L Tracy, Raul I Palomares, Eric C Oquinn, Joerg C Neuefeind, Jason Behrens, Maik LangAbstract:Abstract A major challenge to understanding the response of materials to extreme environments (e.g., nuclear fuels/waste forms and fusion materials) is to unravel the processes by which a material can incorporate atomic-scale disorder, and at the same time, remain crystalline. While it has long been known that all condensed matter, even liquids and glasses, possess short-range order, the relation between fully-ordered, disordered, and aperiodic structures over multiple length scales is not well understood. For example, when defects are introduced (via pressure or irradiation) into materials adopting the Pyrochlore structure, these complex oxides either disorder over specific crystallographic sites, remaining crystalline, or become aperiodic. Here we present neutron total scattering results characterizing the irradiation response of two Pyrochlores, one that is known to disorder (Er2Sn2O7) and the other to amorphize (Dy2Sn2O7) under ion irradiation. The results demonstrate that in both cases, the local Pyrochlore structure is transformed into similar short range configurations that are best fit by the orthorhombic weberite structure, even though the two compositions have distinctly different structures, aperiodic vs. disordered-crystalline, at longer length scales. Thus, a material's resistance to amorphization may not depend primarily on local defect formation energies, but rather on the structure's compatibility with meso-scale modulations of the local order in a way that maintains long-range periodicity.
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Probing disorder in isometric Pyrochlore and related complex oxides
Nature Materials, 2016Co-Authors: Jacob Shamblin, Rodney C. Ewing, Mikhail Feygenson, Sarah Finkeldei, Dirk Bosbach, Cameron L Tracy, Fuxiang Zhang, Joerg Neuefeind, Haidong Zhou, Maik LangAbstract:There has been an increased focus on understanding the energetics of structures with unconventional ordering (for example, correlated disorder that is heterogeneous across different length scales^ 1 ). In particular, compounds with the isometric Pyrochlore structure^ 2 , A_2B_2O_7, can adopt a disordered, isometric fluorite-type structure, (A, B)_4O_7, under extreme conditions^ 3 , 4 , 5 , 6 , 7 . Despite the importance of the disordering process there exists only a limited understanding of the role of local ordering on the energy landscape. We have used neutron total scattering to show that disordered fluorite (induced intrinsically by composition/stoichiometry or at far-from-equilibrium conditions produced by high-energy radiation) consists of a local orthorhombic structural unit that is repeated by a pseudo-translational symmetry, such that orthorhombic and isometric arrays coexist at different length scales. We also show that inversion in isometric spinel occurs by a similar process. This insight provides a new basis for understanding order-to-disorder transformations important for applications such as plutonium immobilization^ 4 , fast ion conduction^ 8 , and thermal barrier coatings^ 9 , 10 . Disordering in complex oxides is important for their radiation resistance. It is now shown that Pyrochlores disorder by the formation of a weberite-like phase, with similar behaviour observed in spinels, adding complexity to their disordering.
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Atomic disorder in Gd2Zr2O7 Pyrochlore
Applied Physics Letters, 2015Co-Authors: Fuxiang Zhang, Maik Lang, Rodney C. EwingAbstract:Gd2Zr2O7 Pyrochlore with different degrees of cation disorder were synthesized by isothermal annealing at various temperatures (1100–1550 °C), and the related changes in the structure were investigated by ambient and high pressure x-ray diffraction (XRD) measurements. Unit cell parameters increase almost linearly with increasing treatment temperature. The degree of cation order in Pyrochlore also increases with the increase of temperature, but saturates at ∼60%. The compressibility of the Pyrochlore structures decreases when the degree of cation order increases. High pressure XRD measurements also indicate that the phase stability of Gd2Zr2O7 is not very sensitive to the degree of atomic disorder in the Pyrochlore structure.
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Heavy Ion Irradiation of Zirconate Pyrochlores
MRS Proceedings, 2011Co-Authors: Jie Lian, Rodney C. Ewing, Lumin Wang, J. Chen, K. V. G. KuttyAbstract:Zirconate Pyrochlores, A 2 Zr 2 O 7 , are important potential nuclear waste forms for Puimmobilization. The binary Gd 2 (Ti 2-x Zr x )O 7 has been shown to have increasing resistance to ionirradiation damage with the increasing Zr content, and Gd 2 Zr 2 O 7 is radiation resistant to a 1 MeV Kr + ion irradiation at 25 K to a dose of 5 dpa. In this study, a 1.5 MeV Xe+ irradiation was completed for zirconate Pyrochlores A 2 Zr 2 O 7 (A=La, Nd, Sm, Gd). The radiation resistance decreases with an increase of the ionic radius of A-site cation. La 2 Zr 2 O 7 is the first zirconate Pyrochlore to be amorphized by ion beam irradiation, and the critical amorphization temperature, Tc, is ∼310 K. The susceptibility of La 2 Zr 2 O 7 to ion beam damage is related to its structure, which shows the largest deviation from the ideal fluorite structure. These results are also consistent with calculations of the cation antisite formation energy in the Pyrochlore structure. The ion irradiation-induced Pyrochlore-to-fluorite transformation occurred in all of the irradiated zirconate Pyrochlore phases. Based on the results for Gd 2 Ti 2-x Zr x O 7 and A 2 Zr 2 O 7 , the defect fluorite structures are stable when the ionic radii ratio r A /r B ≤1.54; beyond this limit, the defect fluorite structure becomes increasingly unstable relative to the amorphous state.
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review of a2b2o7 Pyrochlore response to irradiation and pressure
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2010Co-Authors: Maik Lang, William J. Weber, F X Zhang, Jiaming Zhang, Jianwei Wang, Jie Lian, B Schuster, Christina Trautmann, R Neumann, Rodney C. EwingAbstract:Abstract This article reviews recent research on swift heavy-ion irradiations and high-pressure studies on Pyrochlores of the Gd2Zr2−xTixO7 binary [1] , [2] , [3] , [4] . Applying three complementary analytical techniques (synchrotron X-ray diffraction, Raman spectroscopy and transmission electron microscopy) allowed for the investigation of the response of Pyrochlore to irradiation and/or pressure. The chemical composition of Pyrochlore has a strong effect on the character and energetics of the type of structural modifications that can be obtained under pressure or irradiation: For Ti-rich Pyrochlores, the crystalline-to-amorphous transition is the dominant process. When Zr is substituted for Ti, an order–disorder transformation to the defect-fluorite structure becomes the increasingly dominant process. Except for Gd2Zr2O7, single ion tracks in Pyrochlore consist of an amorphous core, surrounded by a crystalline, but disordered, defect-fluorite shell. This shell is surrounded by a defect-rich Pyrochlore region. In contrast to similar effects observed when pressure or irradiation are applied separately, the response of the Pyrochlore structure is significantly different when it is exposed simultaneously to pressure and irradiation. The combination of relativistic heavy ions with high pressure results in the formation of a new metastable Pyrochlore phase. TEM and quantum–mechanical calculations suggest that these novel structural modifications are caused by the formation of nanocrystals and the modified energetics of nanomaterials.
Narottam P Bansal - One of the best experts on this subject based on the ideXlab platform.
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effects of doping on thermal conductivity of Pyrochlore oxides for advanced thermal barrier coatings
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2007Co-Authors: Narottam P BansalAbstract:Abstract Pyrochlore oxides of general composition, A 2 B 2 O 7 , where A is a 3+ cation (La to Lu) and B is a 4+ cation (Zr, Hf, Ti, etc) have high melting point, relatively high coefficient of thermal expansion, and low thermal conductivity which make them suitable for applications as high-temperature thermal barrier coatings. The effect of doping at the A site on the thermal conductivity of a Pyrochlore oxide La 2 Zr 2 O 7, has been investigated. Oxide powders of various compositions La 2 Zr 2 O 7, La 1.7 Gd 0.3 Zr 2 O 7 , La 1.7 Yb 0.3 Zr 2 O 7 and La 1.7 Gd 0.15 Yb 0.15 Zr 2 O 7 were synthesized by the citric acid sol-gel method. These powders were hot pressed into discs and used for thermal conductivity measurements using a steady-state laser heat flux test technique. The rare earth oxide doped Pyrochlores La 1.7 Gd 0.3 Zr 2 O 7 , La 1.7 Yb 0.3 Zr 2 O 7 and La 1.7 Gd 0.15 Yb 0.15 Zr 2 O 7 had lower thermal conductivity than the un-doped La 2 Zr 2 O 7 . The Gd 2 O 3 and Yb 2 O 3
Romain Sibille - One of the best experts on this subject based on the ideXlab platform.
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A quantum liquid of magnetic octupoles on the Pyrochlore lattice
Nature Physics, 2020Co-Authors: Romain Sibille, Nicolas Gauthier, Elsa Lhotel, Victor Porée, Vladimir Pomjakushin, Russell A. Ewings, Toby G. Perring, Jacques Ollivier, Andrew Wildes, Clemens RitterAbstract:A detailed neutron-scattering study reveals a quantum spin liquid behaviour in Ce_2Sn_2O_7 originating from its higher-order magnetic multipolar moments acting on the geometrically frustrated Pyrochlore lattice. Spin liquids are highly correlated yet disordered states formed by the entanglement of magnetic dipoles^ 1 . Theories define such states using gauge fields and deconfined quasiparticle excitations that emerge from a local constraint governing the ground state of a frustrated magnet. For example, the ‘2-in–2-out’ ice rule for dipole moments on a tetrahedron can lead to a quantum spin ice^ 2 – 4 in rare-earth Pyrochlores. However, f -electron ions often carry multipole degrees of freedom of higher rank than dipoles, leading to intriguing behaviours and ‘hidden’ orders^ 5 , 6 . Here we show that the correlated ground state of a Ce^3+-based Pyrochlore, Ce_2Sn_2O_7, is a quantum liquid of magnetic octupoles. Our neutron scattering results are consistent with a fluid-like state where degrees of freedom have a more complex magnetization density than that of magnetic dipoles. The nature and strength of the octupole–octupole couplings, together with the existence of a continuum of excitations attributed to spinons, provides further evidence for a quantum ice of octupoles governed by a ‘2-plus–2-minus’ rule^ 7 , 8 . Our work identifies Ce_2Sn_2O_7 as a unique example of frustrated multipoles forming a ‘hidden’ topological order, thus generalizing observations on quantum spin liquids to multipolar phases that can support novel types of emergent fields and excitations.
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a quantum liquid of magnetic octupoles on the Pyrochlore lattice
arXiv: Strongly Correlated Electrons, 2019Co-Authors: Romain Sibille, Nicolas Gauthier, Elsa Lhotel, Victor Porée, Vladimir Pomjakushin, Russell A. Ewings, Toby G. Perring, Jacques Ollivier, Andrew Wildes, Clemens RitterAbstract:Spin liquids are highly correlated yet disordered states formed by the entanglement of magnetic dipoles$^1$. Theories typically define such states using gauge fields and deconfined quasiparticle excitations that emerge from a simple rule governing the local ground state of a frustrated magnet. For example, the '2-in-2-out' ice rule for dipole moments on a tetrahedron can lead to a quantum spin ice in rare-earth Pyrochlores - a state described by a lattice gauge theory of quantum electrodynamics$^{2-4}$. However, f-electron ions often carry multipole degrees of freedom of higher rank than dipoles, leading to intriguing behaviours and 'hidden' orders$^{5-6}$. Here we show that the correlated ground state of a Ce$^{3+}$-based Pyrochlore, Ce$_2$Sn$_2$O$_7$, is a quantum liquid of magnetic octupoles. Our neutron scattering results are consistent with the formation of a fluid-like state of matter, but the intensity distribution is weighted to larger scattering vectors, which indicates that the correlated degrees of freedom have a more complex magnetization density than that typical of magnetic dipoles in a spin liquid. The temperature evolution of the bulk properties in the correlated regime below 1 Kelvin is well reproduced using a model of dipole-octupole doublets on a Pyrochlore lattice$^{7-8}$. The nature and strength of the octupole-octupole couplings, together with the existence of a continuum of excitations attributed to spinons, provides further evidence for a quantum ice of octupoles governed by a '2-plus-2-minus' rule. Our work identifies Ce$_2$Sn$_2$O$_7$ as a unique example of a material where frustrated multipoles form a 'hidden' topological order, thus generalizing observations on quantum spin liquids to multipolar phases that can support novel types of emergent fields and excitations.
Jie Lian - One of the best experts on this subject based on the ideXlab platform.
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Heavy Ion Irradiation of Zirconate Pyrochlores
MRS Proceedings, 2011Co-Authors: Jie Lian, Rodney C. Ewing, Lumin Wang, J. Chen, K. V. G. KuttyAbstract:Zirconate Pyrochlores, A 2 Zr 2 O 7 , are important potential nuclear waste forms for Puimmobilization. The binary Gd 2 (Ti 2-x Zr x )O 7 has been shown to have increasing resistance to ionirradiation damage with the increasing Zr content, and Gd 2 Zr 2 O 7 is radiation resistant to a 1 MeV Kr + ion irradiation at 25 K to a dose of 5 dpa. In this study, a 1.5 MeV Xe+ irradiation was completed for zirconate Pyrochlores A 2 Zr 2 O 7 (A=La, Nd, Sm, Gd). The radiation resistance decreases with an increase of the ionic radius of A-site cation. La 2 Zr 2 O 7 is the first zirconate Pyrochlore to be amorphized by ion beam irradiation, and the critical amorphization temperature, Tc, is ∼310 K. The susceptibility of La 2 Zr 2 O 7 to ion beam damage is related to its structure, which shows the largest deviation from the ideal fluorite structure. These results are also consistent with calculations of the cation antisite formation energy in the Pyrochlore structure. The ion irradiation-induced Pyrochlore-to-fluorite transformation occurred in all of the irradiated zirconate Pyrochlore phases. Based on the results for Gd 2 Ti 2-x Zr x O 7 and A 2 Zr 2 O 7 , the defect fluorite structures are stable when the ionic radii ratio r A /r B ≤1.54; beyond this limit, the defect fluorite structure becomes increasingly unstable relative to the amorphous state.
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review of a2b2o7 Pyrochlore response to irradiation and pressure
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2010Co-Authors: Maik Lang, William J. Weber, F X Zhang, Jiaming Zhang, Jianwei Wang, Jie Lian, B Schuster, Christina Trautmann, R Neumann, Rodney C. EwingAbstract:Abstract This article reviews recent research on swift heavy-ion irradiations and high-pressure studies on Pyrochlores of the Gd2Zr2−xTixO7 binary [1] , [2] , [3] , [4] . Applying three complementary analytical techniques (synchrotron X-ray diffraction, Raman spectroscopy and transmission electron microscopy) allowed for the investigation of the response of Pyrochlore to irradiation and/or pressure. The chemical composition of Pyrochlore has a strong effect on the character and energetics of the type of structural modifications that can be obtained under pressure or irradiation: For Ti-rich Pyrochlores, the crystalline-to-amorphous transition is the dominant process. When Zr is substituted for Ti, an order–disorder transformation to the defect-fluorite structure becomes the increasingly dominant process. Except for Gd2Zr2O7, single ion tracks in Pyrochlore consist of an amorphous core, surrounded by a crystalline, but disordered, defect-fluorite shell. This shell is surrounded by a defect-rich Pyrochlore region. In contrast to similar effects observed when pressure or irradiation are applied separately, the response of the Pyrochlore structure is significantly different when it is exposed simultaneously to pressure and irradiation. The combination of relativistic heavy ions with high pressure results in the formation of a new metastable Pyrochlore phase. TEM and quantum–mechanical calculations suggest that these novel structural modifications are caused by the formation of nanocrystals and the modified energetics of nanomaterials.
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Radiation-induced effects in Pyrochlores and nanoscale materials engineering
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2006Co-Authors: Jie Lian, William J. Weber, Weilin Jiang, Lumin Wang, Lynn A. Boatner, Rodney C. EwingAbstract:Abstract Pyrochlore materials, A2B2O7, encompass a wide range of compositions and are technologically important for energy and environmental issues. For example, they may be used as ionic conductors in solid oxide fuel cells or nuclear waste forms for the storage of actinides, particularly Pu. Here, the recent progress in understanding ion beam irradiation-induced phenomena in Pyrochlore compounds is briefly reviewed with a focus on the ion beam-induced crystalline-to-amorphous and Pyrochlore-to-fluorite structural transitions. Systematic ion irradiation studies of lanthanide Pyrochlores with B = Ti, Zr and Sn have indicated that the radiation response of the Pyrochlore compounds is highly dependent on compositional changes. Both the ionic size and cation electronic configurations (e.g. bond-types) affect the structural distortion from the ideal fluorite structure and thus the response of Pyrochlore-structure types to ion beam irradiation. An ion beam-induced Pyrochlore-to-fluorite structural transition occurs in all irradiated Pyrochlore compositions, and the independent kinetics of the cation and anion disordering processes has been discussed. Numerous novel nanostructures have been created by utilizing the ion beam-induced amorphization, order–disorder transition and phase decomposition, such as amorphous and disordered nano-domains, perfectly lattice matched two-dimensional nanolayers, self-organized ripple structures, metallic nanoparticles and nanowires.
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the order disorder transition in ion irradiated Pyrochlore
Acta Materialia, 2003Co-Authors: Jie Lian, Rodney C. Ewing, Lumin Wang, J. Chen, Matt J Farmer, L A BoatnerAbstract:Abstract A radiation-induced order–disorder transformation occurs in many A 2 B 2 O 7 Pyrochlore structure-types by disordering of the A- and B-site cations, as well as anion vacancies. The ionic conductivity increases up to two orders of magnitude due to this order–disorder transformation. This irradiation-induced order–disorder transition has been examined in detail using ion beam irradiations and in situ transmission electron microscopy. Under ion irradiation, the ordered Pyrochlore superstructure transforms to an anion-disordered Pyrochlore prior to a final transformation to a cation-disordered defect-fluorite structure-type. The anion-disordered Pyrochlore structure displays a partial ordering of the A- and B-site cations and complete disordering on the anion array—as evidenced by the disappearance of characteristic diffraction maxima resulting from ordering of the oxygen sublattice. These results suggest that anion disorder precedes cation disordering in the Pyrochlore structure.
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ion irradiation induced amorphization of la 2 zr 2 o 7 Pyrochlore
Physical Review B, 2002Co-Authors: Jie Lian, L.m. Wang, K. V. G. Kutty, X T Zu, Jie Chen, Rodney C. EwingAbstract:The isometric Pyrochlore structure, ${A}_{2}{B}_{2}{\mathrm{O}}_{7},$ is generally susceptible to radiation damage, but certain compositions are remarkably resistant to radiation damage. In the binary system ${\mathrm{Gd}}_{2}({\mathrm{Ti}}_{2\ensuremath{-}x}{\mathrm{Zr}}_{x}){\mathrm{O}}_{7},$ the radiation resistance increases dramatically with the substitution of Zr for Ti, until the pure end member ${\mathrm{Gd}}_{2}{\mathrm{Zr}}_{2}{\mathrm{O}}_{7}$ cannot be amorphized, even at doses as high as \ensuremath{\sim}100 dpa. Although zirconate Pyrochlores are generally considered to be radiation resistant, we report results for the amorphization of a zirconate Pyrochlore ${\mathrm{La}}_{2}{\mathrm{Zr}}_{2}{\mathrm{O}}_{7}$ by ion beam irradiation (\ensuremath{\sim}5.5 dpa at room temperature). The critical amorphization temperature ${T}_{c}$ is low, \ensuremath{\sim}310 K. The susceptibility to ion-beam-induced amorphization and structural disordering for zirconate Pyrochlores is related to the structural deviation from the ideal fluorite structure, as reflected by the x parameter of the ${\mathrm{O}}_{48f}.$
