Search results for "conductivity"
showing 10 items of 1988 documents
LiCrO2 Under Pressure: In-Situ Structural and Vibrational Studies
2018
The high-pressure behaviour of LiCrO2, a compound isostructural to the battery compound LiCoO2, has been investigated by synchrotron-based angle-dispersive X-ray powder diffraction, Raman spectroscopy, and resistance measurements up to 41, 30, and 10 Gpa, respectively. The stability of the layered structured compound on a triangular lattice with R-3m space group is confirmed in all three measurements up to the highest pressure reached. The dependence of lattice parameters and unit-cell volume with pressure has been determined from the structural refinements of X-ray diffraction patterns that are used to extract the axial compressibilities and bulk modulus by means of Birch&ndash
Devil’s vortex-lenses
2009
In this paper we present a new kind of vortex lenses in which the radial phase distribution is characterized by the "devil's staircase" function. The focusing properties of these fractal DOEs coined Devil's vortex-lenses are analytically studied and the influence of the topological charge is investigated. It is shown that under monochromatic illumination a vortex devil's lens give rise a focal volume containing a delimited chain of vortices that are axially distributed according to the self-similarity of the lens.
Melting curve and phase diagram of vanadium under high-pressure and high-temperature conditions
2019
Melting curve and phase diagram of vanadium under high-pressure and high-temperature conditions We report a combined experimental and theoretical study of the melting curve and the structural behavior of vanadium under extreme pressure and temperature. We performed powder x-ray-diffraction experiments up to 120 GPa and 4000 K, determining the phase boundary of the body-centered cubic-to-rhombohedral transition and melting temperatures at different pressures. Melting temperatures have also been established from the observation of temperature plateaus during laser heating, and the results from the density-functional theory calculations. Results obtained from our experiments and calculations a…
Giant conductivity enhancement: Pressure-induced semiconductor-metal phase transition in Cd0.90Zn0.1Te
2019
Element doping and pressure compression may change material properties for improved performance in applications. We report pressure-induced metallization in the semiconductor $\mathrm{C}{\mathrm{d}}_{0.90}\mathrm{Z}{\mathrm{n}}_{0.1}\mathrm{Te}$. Transport measurements showed an overall resistivity drop of 11 orders of magnitude under compression up to 12 GPa, which is indicative of a metallization transition. X-ray diffraction measurements revealed that the sample underwent a structural transition from a cubic-$F4\overline{3}m$ phase (zinc blende) to a cubic-$Fm\overline{3}m$ phase (rock salt) at about 5.5 GPa, followed by another transition to an orthorhombic $Cmcm$ structure at 13 GPa. A…
X-ray Studies of Debye Temperature of Some ABO 3 Perovskites
2002
Debye temperatures T D of some perovskite compounds are determined by X-ray diffraction. Correlation between T D determined at T=180 °C, mean square displacements of atoms, quasi-elastic coupling, and melting temperature of the perovskite compounds is analysed.
High-pressure/high-temperature phase diagram of zinc
2018
The phase diagram of zinc (Zn) has been explored up to 140 GPa and 6000K, by combining optical observations, x-ray diffraction, and ab initio calculations. In the pressure range covered by this study, Zn is found to retain a hexagonal close-packed (hcp) crystal symmetry up to the melting temperature. The known decrease of the axial ratio (c/a) of the hcp phase of Zn under compression is observed in x-ray diffraction experiments from 300K up to the melting temperature. The pressure at which c/a reaches root 3 (approximate to 10GPa) is slightly affected by temperature. When this axial ratio is reached, we observed that single crystals of Zn, formed at high temperature, break into multiple pol…
High proton conduction in a chiral ferromagnetic metal-organic quartz-like framework.
2011
A complex-as-ligand strategy to get a multifunctional molecular material led to a metal-organic framework with the formula (NH(4))(4)[MnCr(2)(ox)(6)]·4H(2)O. Single-crystal X-ray diffraction revealed that the anionic bimetallic coordination network adopts a chiral three-dimensional quartz-like architecture. It hosts ammonium cations and water molecules in functionalized channels. In addition to ferromagnetic ordering below T(C) = 3.0 K related to the host network, the material exhibits a very high proton conductivity of 1.1 × 10(-3) S cm(-1) at room temperature due to the guest molecules.
Modified YBCO superconductor-ferroelectric composites: Bulk materials and thick films
1996
Bulk samples and 50–125 μm thick films of (1-x)YBa2Cu3O7−δ-xBaTiO3 (0⩽x⩽0.12 by weight) composites have been synthesized, the films being obtained by Stokes sedimentation on SrTiO3 ceramic plates and firing in oxygen by Melt Textured Growth techniques. The phase composition and texture have been studied by X-ray diffraction and microstructure. Resistance and magnetic susceptibility of prepared samples have been measured.
Pressure effect on superconductivity in FeSe0.5Te0.5
2016
Due to the simple layered structure, isostructural FeSe and FeSe0.5Te0.5 are clue compounds for understanding the principal mechanisms of superconductivity in the family of Fe-based superconductors. High-pressure magnetic, structural and Mossbauer studies have been performed on single-crystalline samples of superconducting FeSe0.5Te0.5 with Tc = 13.5 K. Susceptibility data have revealed a strong increase of Tc up to 19.5 K for pressures up to 1.3 GPa, followed by a plateau in the Tc(p) dependence up to 5.0 GPa. Further pressure increase leads to a disappearance of the superconducting state around 7.0 GPa. X-ray diffraction and Mossbauer studies explain this fact by a tetragonal-to-hexagonal…
Pressure-restored superconductivity in Cu-substituted FeSe
2011
Copper doping of FeSe destroys its superconductivity at ambient pressure, even at low doping levels. Here we report the pressure-dependent transport and structural properties of Fe${}_{1.01\ensuremath{-}x}$Cu${}_{x}$Se with 3$%$ and 4$%$ Cu doping and find that the superconductivity is restored. Metallic resistivity behavior, absent in Cu-doped FeSe, is also restored. At the low pressure of 1.5 GPa, superconductivity is seen at 6 K for 4$%$ Cu doping, somewhat lower than the 8 K ${T}_{c}$ of undoped FeSe. ${T}_{c}$ reaches its maximum of 31.3 K at 7.8 GPa, lower than the maximum superconducting temperature in the undoped material under pressure (${T}_{c}$ max of 37 K) but still very high. X…