High-pressure polymorph of CoPO: phase transition to an olivine-related structure.

The monoclinic polymorph of CoPO (space group 2/), isomorphic to farringtonite (MgPO) type orthophosphates, was studied up to 21 GPa using synchrotron powder X-ray diffraction and density-functional theory simulations to investigate the influence of pressure in the crystal structure. This study revealed a pressure induced structural phase transition for monoclinic cobalt phosphate, CoPO, and the details of crystal structure of the new high-pressure polymorph were delineated. The evolution of XRD pattern with pressure indicate that the onset of a phase transition occurs around 2.

Evidence of Strong Orbital-Selective Spin-Orbital-Phonon Coupling in CrVO_{4}.

Coupling of orbital degree of freedom with a spin exchange, i.e., Kugel-Khomskii-type interaction (KK), governs a host of material properties, including colossal magnetoresistance, enhanced magnetoelectric response, and photoinduced high-temperature magnetism.

Equations of State and Crystal Structures of KCaPO, KSrPO, and KCe(PO) under High Pressure: Discovery of a New Polymorph of KCaPO.

We have studied by means of angle-dispersive powder synchrotron X-ray diffraction the structural behavior of KCaPO, SrKPO, and KCe(PO) under high pressure up to 26, 25, and 22 GPa, respectively. For KCaPO, we have also accurately determined the crystal structure under ambient conditions, which differs from the structure previously reported. Arguments supporting our structural determination will be discussed.

High-Pressure X-ray Diffraction Study of Orthorhombic CaZrTiO.

The orthorhombic polymorph of CaZrTiO (space group ) has been studied by powder X-ray diffraction under high pressures up to 30 GPa using synchrotron radiation. We have found evidence of a structural phase transition at 12-13 GPa. The phase transition causes an enhancement of the crystal symmetry.

Novel application of sodium manganese oxide in removing acidic gases in ambient conditions.

In this study, we have demonstrated the application of sodium manganese oxide for the chemisorption of toxic acidic gases at room temperature. The fabricated alkali ceramic has NaMnO, NaMnO, and NaMnO phases with a surface area of 2.6 m g.

Fabrication of NaMnO Microrods for Room-Temperature Oxidation of Sulfurous Gases.

Phase pure NaMnO microrods crystallized in the orthorhombic symmetry were fabricated for the wet oxidation of HS and SO gases at room temperature. The material was found highly effective for the mineralization of low concentrations of acidic gases. The material was fully regenerable after soaking in a basic HO solution.

Lattice dynamics of zircon-type NdVOand scheelite-type PrVOunder high-pressure.

Zircon-type NdVOand scheelite-type PrVOhave been studied by means of Raman spectroscopy up to approximately 20 GPa. In the first compound, zircon-scheelite and scheelite-fergusonite phase transitions are reported at 6.4(3) and 19.

Phonon and magnetoelastic coupling in AlGaFeO: Raman, magnetization and neutron diffraction studies.

The intriguing coupling phenomena among spin, phonon, and charge degrees of freedom in materials having magnetic, ferroelectric and/or ferroelastic order have been of research interest for the fundamental understanding and technological relevance. We report a detailed study on structure and phonons of AlGaFeO (ALGF), a lead-free magnetoelectric material, carried out using variable temperature dependent powder neutron diffraction and Raman spectroscopy. Neutron diffraction studies suggest that Al ions are distributed in one tetrahedrally (BO) and three octahedrally (BO) coordinated sites of the orthorhombic (Pc2n) structure and there is no structural transition in the temperature range of 7-800 K.

Structural Characterization of Aurophilic Gold(I) Iodide under High Pressure.

The effects of pressure on the crystal structure of aurophilic tetragonal gold iodide have been studied by means of powder X-ray diffraction up to 13.5 GPa. We found evidence of the onset of a phase transition at 1.

Pressure-Induced Hexagonal to Monoclinic Phase Transition of Partially Hydrated CePO.

We present a study of the pressure dependence of the structure of partially hydrated hexagonal CePO up to 21 GPa using synchrotron powder X-ray diffraction. At a pressure of 10 GPa, a second-order structural phase transition is observed, associated with a novel polymorph. The previously unknown high-pressure phase has a monoclinic structure with a similar atomic arrangement as the low-pressure phase, but with reduced symmetry, belonging to space group C2.

High-Pressure High-Temperature Stability and Thermal Equation of State of Zircon-Type Erbium Vanadate.

The zircon to scheelite phase boundary of ErVO has been studied by high-pressure and high-temperature powder and single-crystal X-ray diffraction. This study has allowed us to delimit the best synthesis conditions of its scheelite-type phase, determine the ambient-temperature equation of state of the zircon and scheelite-type structures, and obtain the thermal equation of state of the zircon-type polymorph. The results obtained with powder samples indicate that zircon-type ErVO transforms to scheelite at 8.

Stability of FeVO under Pressure: An X-ray Diffraction and First-Principles Study.

The high-pressure behavior of the crystalline structure FeVO has been studied by means of X-ray diffraction using a diamond-anvil cell and first-principles calculations. The experiments were carried out up to a pressure of 12.3 GPa, until now the highest pressure reached to study an FeVO compound.

High Pressure Phases and Amorphization of a Negative Thermal Expansion Compound TaVO.

Negative thermal expansion material TaVO is recently reported to have pressure induced structural phase transition and irreversible amorphization at 0.2 and above 8 GPa, respectively. Here, we have investigated the high pressure phase of TaVO using in situ neutron diffraction studies.

Pressure and Temperature Dependent Structural Studies on Hollandite Type Ferrotitanate and Crystal Structure of a High Pressure Phase.

The structural stability and phase transition behavior of tetragonal (I4/m) hollandite type KFeTiO have been investigated by in situ high pressure X-ray diffraction using synchrotron radiation and a diamond anvil cell as well as by variable temperature powder neutron and X-ray diffraction. The tetragonal phase is found to be stable in a wider range of temperatures, while it reversibly transforms to a monoclinic (I2/m) structure at a moderate pressure, viz. 3.

High-pressure structural and vibrational properties of monazite-type BiPO, LaPO, CePO, and PrPO.

Monazite-type BiPO, LaPO, CePO, and PrPO have been studied under high pressure by ab initio simulations and Raman spectroscopy measurements in the pressure range of stability of the monazite structure. A good agreement between experimental and theoretical Raman-active mode frequencies and pressure coefficients has been found which has allowed us to discuss the nature of the Raman-active modes. Besides, calculations have provided us with information on how the crystal structure is modified by pressure.

Pressure Impact on the Stability and Distortion of the Crystal Structure of CeScO.

The effects of high pressure on the crystal structure of orthorhombic (Pnma) perovskite-type cerium scandate were studied in situ under high pressure by means of synchrotron X-ray powder diffraction, using a diamond-anvil cell. We found that the perovskite-type crystal structure remains stable up to 40 GPa, the highest pressure reached in the experiments. The evolution of unit-cell parameters with pressure indicated an anisotropic compression.

Superionic conduction in β-eucryptite: inelastic neutron scattering and computational studies.

β-Eucryptite (LiAlSiO) is known to show super-ionic conductivity above 700 K. We performed inelastic neutron scattering measurements in β-eucryptite over 300-900 K and calculated the phonon spectrum using classical molecular dynamics (MD) simulations. The MD simulations were used to interpret the inelastic neutron spectra at high temperatures.

Structural and vibrational properties of corundum-type InO nanocrystals under compression.

This work reports the structural and vibrational properties of nanocrystals of corundum-type InO (rh-InO) at high pressures by using angle-dispersive x-ray diffraction and Raman scattering measurements up to 30 GPa. The equation of state and the pressure dependence of the Raman-active modes of the corundum phase in nanocrystals are in good agreement with previous studies on bulk material and theoretical simulations on bulk rh-InO. Nanocrystalline rh-InO showed stability under compression at least up to 20 GPa, unlike bulk rh-InO which gradually transforms to the orthorhombic Pbca (RhO-III-type) structure above 12-14 GPa.

Phase Transformation, Vibrational and Electronic Properties of KCe(PO): A Combined Experimental and Theoretical Study.

Herein we report the high-temperature crystal chemistry of KCe(PO) as observed from a joint in situ variable-temperature X-ray diffraction (XRD) and Raman spectroscopy as well as ab initio density functional theory (DFT) calculations. These studies revealed that the ambient-temperature monoclinic (P2/n) phase reversibly transforms to a tetragonal (I4/amd) structure at higher temperature. Also, from the experimental and theoretical calculations, a possible existence of an orthorhombic (Imma) structure with almost zero orthorhombicity is predicted which is closely related to tetragonal KCe(PO).

Temperature dependent structural, vibrational and magnetic properties of KGd(PO).

Herein we report the evolution of the crystal structure of KGd(PO) in the temperature range from 20 K to 1073 K, as observed from variable temperature X-ray diffraction and Raman spectroscopic studies. KGd(PO) has an open tunnel containing a three dimensional structure built by [Gd(PO)] ions which in turn are formed of PO tetrahedra and GdO (n = 8 and 9) polyhedra. The empty tunnels in the structure are occupied by K ions and maintain charge neutrality in the lattice.

Structural Stability and Anharmonicity of PrTiO: Raman Spectroscopic and XRD Studies.

Herein we report results of pressure- and temperature-dependent Raman scattering studies on PrTiO. Pressure-dependent studies performed up to 23 GPa suggest a reversible phase transition above 15 GPa with subtle changes. Temperature-dependent investigations performed in the range of 77-1073 K showed anomalous temperature dependence of some of the Raman modes.

Structural manipulation and tailoring of dielectric properties in SrTi1-xFexTaxO3 perovskites: Design of new lead free relaxors.

We report composition dependent structure evolution from SrTiO3 to SrFe0.5Ta0.5O3 by powder X-ray and neutron diffraction studies of SrTi1-2xFexTaxO3 (0.

Structural and Thermal Properties of BaTe2O6: Combined Variable-Temperature Synchrotron X-ray Diffraction, Raman Spectroscopy, and ab Initio Calculations.

Variable-temperature Raman spectroscopic and synchrotron X-ray diffraction studies were performed on BaTe2O6 (orthorhombic, space group: Cmcm), a mixed-valence tellurium compound with a layered structure, to understand structural stability and anharmonicity of phonons. The structural and vibrational studies indicate no phase transition in it over a wider range of temperature (20 to 853 K). The structure shows anisotropic expansion with coefficients of thermal expansion in the order αb ≫ αa > αc, which was attributed to the anisotropy in bonding and structure of BaTe2O6.

High-Pressure Crystal Structure, Lattice Vibrations, and Band Structure of BiSbO4.

The high-pressure crystal structure, lattice-vibrations, and electronic band structure of BiSbO4 were studied by ab initio simulations. We also performed Raman spectroscopy, infrared spectroscopy, and diffuse-reflectance measurements, as well as synchrotron powder X-ray diffraction. High-pressure X-ray diffraction measurements show that the crystal structure of BiSbO4 remains stable up to at least 70 GPa, unlike other known MTO4-type ternary oxides.