T. V. D'yachkova

New elaboration technique, structure and physical properties of infinite-layer Sr1−xLnxCuO2(Ln = Nd, Pr)

Abstract The infinite-layer compounds of the (Sr, Ln)CuO 2 family have been prepared by a new synthesis method from the low-pressure phase of SrCuO 2 and NdCuO 2 as starting materials. The crystal structure, microstructure and superconductivity of these samples have been studied with use of neutron powder diffraction, optical micrographs, energy-dispersive X-ray analysis. magnetic-susceptibility and electrical-resistivity measurements. The ratio of the lattice constants a/c as an empirical parameter for the existence of superconductivity in the electron-doped infinite-layer compounds is discussed.

Na0.25Cu0.75VO3: A New Perovskite-like Vanadium Bronze

A new cubic perovskite-like vanadium bronze of composition Na0.25Cu0.75VO3 , with a lattice parameter of 7.2517(1) Å, is obtained by reacting NaVO3 , V2O5 , and Cu2O at 1100°C and 8 GPa. It exhibits metallic conduction, with a sharp change in resistivity above 200°C, and, presumably, undergoes a phase transition near 280°C. The thermal properties of the new vanadium bronze are studied in air and helium at normal pressure.

63Cu NMR study of infinite-layer compound Sr1−xLaxCuO2

Abstract We present the 63 Cu NMR studies on powder samples of an electron-doped infinite-layer high- T c cuprate superconductors Sr 1− x La x CuO 2 ( x =0, 0.07, 0.16). We have found the decrease of magnetic shift due to the superconducting transition. The temperature dependence of the spin-lattice relaxation rate ( T 1 T ) −1 demonstrates non-Korringa Curie–Weiss like behavior in normal state. These results are very similar to the general case of hole-doped high- T c superconductors. The decrease of the quadrupolar frequency with increasing the doping level has been found.

Synthesis, crystal structure and inelastic neutron scattering in the infinite-layer compounds Sr1−xNdxCuO2

Abstract For the first time large samples of the nominal composition Sr 1− x Nd x CuO 2 ( x =0.07, 0.15) 10 g in mass each have been prepared using a high-pressure technique. Neutron-diffraction and X-ray measurements have shown that the main phase in the samples obtained is of the infinite-layer structure which has been refined in the tetragonal P4/mmm space group. Both samples are not superconducting. Inelastic neutron scattering has been employed to search for crystalline-electric-field transitions in these compounds. The observed low-energy spectra exhibit one inelastic line of magnetic origin at 18 meV, comparable in energy with a crystalline-electric-field excitation in the high- T c superconductor NdBa 2 Cu 3 O x .

New MnO–Nb(Ta)2O5 Phases Produced at High Pressures and Temperatures

Phase formation at high pressures and temperatures were studied in the MnO–Nb(Ta)2O5 system. New rhombohedral modifications of Mn4Nb2O9 and Mn4Ta2O9, two new modifications of MnTa2O6, and two modifications of Mn2Ta2O7 were obtained. They were structurally identified.

Synthesis and Structure of Sr1-xLixCuO2 (0<x<:0.15) Phases Produced at High Temperatures and Pressures

We studied the possibility of synthesizing infinite‐layer (IL) phases of Sr1-xLixCuO2 (0<x<1) composition from both orthorhombic Sr1-xLixCuO2 (0 < x < 1) solid solutions and from the corresponding cuprates, SrCuO2 and Li2CuO2, at high pressures (P = 4–8 GPa) and high temperatures (T = 600–1000°). The optimal conditions for synthesis of the IL phases are P = 4 GPa, T = 800°gr, and τ = 2 min. At high pressures and temperatures, the components of the SrCuO2–LiCuO2 system show limited mutual solubility. Sr1-xLixCuO2 solid solutions exist at 0 < x < 0.15. The relationship between the unit cell parameters and Li content of high‐pressure Sr1-xLixCuO2 phases has been established.

Synthesis of (Sr1 – xCax)1 – yCuO2(0 < x< 0.86, 0 < y < 0.1) at High Pressures and Temperatures

Abstract(Sr1 – xCax )1 – yCuO2(0 <x< 0.86, 0 < y< 0.1) infinite-layer solid solutions were prepared at high pressures and temperatures using low-pressure, orthorhombic Sr1 – xCaxCuO2as a precursor, and their low-temperature magnetic susceptibility was measured.

Neutron powder diffraction study of the infinite-layer compounds Sr1−xNdxCuO2☆

Abstract The infinite-layer (IL) systems have rather simple crystal structures and thereby offer an ideal system for an improved understanding of the phenomenon of high-Tc superconductivity. The production of IL compounds is by no means trivial, since the synthesis of single-phase material requires both high pressures and high temperatures. The infinite-layer compounds of the (Sr, Ln)CuO2 family have been prepared by a new synthesis method from the low-pressure phase of SrCuO2 and NdCuO2 as starting materials. The actual rare-earth content in the IL phase is shown to depend on both temperature and pressure. Crystal structure of the IL samples have been studied using neutron powder diffraction and X-ray measurements.

Structural mechanism of oxygen implantation in the vanadium carbide lattice

ConclusionsAn investigation was carried out into the variation of the completeness of the elementary cell of the VCxOy phase forming during the progressive implantation of oxygen into the lattices of the carbides VC0.7−0.9, and the types of solid solutions forming under these conditions were determined. The hypothesis is advanced that metal evolution in this process can be a result also of a redistribution of atoms within the matrix being formed, with the appearance of new elementary cells. In addition, the possibility cannot be ruled out of disproportionation reactions occurring during the oxidation of, inter alia, VCx and VCxOy phases.