Colossal Electric Conductivity in Ag-defect Ag5Pb2O6

Bystroem-Evers compound Ag5 Pb2O6 has been annealed at 500-540 K under flow of electric current which results in a textured structure and anisotropic colossal electric conductivity (> 10^9 ohm-1cm-1) between 210-525 K. The related physical properties are primarly governed by dissociation of Ag from c-axis channels and lattice strains which in turn depend upon electric current.Comment: 13 pages, 7 figure

Some Resistive Properties of Novel Oxide Conductors Cu28-m Pbm-x Ax-p Mp Oy (A, M = Ba, Sr, Ag)

Oxide conductors have been prepared starting from the composition with the unit cell formula Cu24Pb4032 which corresponds to the compound with NaCl type structure referred to in the literature as mineral murdochite. The Pb4+ ions are partly substituted by ions of lower valency like Sr2+, Ba2+ and this results in oxidation of copper (Cu2+ Cu3+) which in turn esta blishes mixed valency states (MVS). The general unit cell formula Cu28-m Pbm_x Ax_p Mp Oy can be proposed and variation of parameters m, p, x with permutation of ions A and M results in a pronounced conductivity of samples at room temperature (RT). Some of them exhibit downturn of the electrical resistance (DER) by cooling from 230 K — 350 K. Since the electrical resistance is enhanced by application of higher current densities in the temperature range where the DER occurs, metallic derivatives of murdochite obtained by substitution of Cu and Pb can be used as interesting candidates for the searching of superconductivity (SC) at T > 200 K

Possible Superconducting State up to 210 K in the new Composition of Y-Ba-Cu-O

We have observed the zero resistance state up to 210 K in the mixed system of nominal composition Yj.2BaOSCu04-prepared under simultaneous action oi pulsed electric field up to 30 kV/cm and uniaxial force of 180 kN. The onset of the decrease of the resistance at 281 K in the repeated cycles and preliminary data diamagnetism are understood by us as a possible superconductivity event related to a particular composition