OPTIMIZATION OF CONDITIONS FOR DISSIPATION-FREE TRANSFER OF ELECTRIC CURRENT USING TWO-LEVEL GRANULAR HIGH- TEMPERATURE SUPERCONDUCTORS OF VARIOUS COMPOSITIONS

In order to optimize the conditions for dissipative-free electric current transport, the influence of chemical composition, temperature and magnetic field on phase transitions in model HTSC objects – granular high-temperature superconductors YBa2Cu3O7-δ and DyBa2Cu3O7-δ – was studied. The work investigated the peculiarities of magnetic field penetration into granular high-temperature superconductors of the 1:2:3 type, depending on the presence or absence of magnetically active atoms in their crystal lattice.Large-scale measurements of specific electrical resistance were carried out under conditions of continuous temperature change and discrete change in the external perpendicular magnetic field strength at a constant value of the transport current density. The influence of the nature of filling the electron shells of the central atoms (Y or REM) in the 1:2:3 HTSC crystal lattice on the occurrence of phase transitions in superconducting granules and in the Josephson medium was investigated. It is shown that the presence of a magnetoactive Dy atom in the HTSC crystal structure has a weak effect on the critical temperatures of phase transitions in superconducting granules, but leads to a significant decrease in the critical temperatures of phase transitions in the Josephson medium. Thus, it is shown that from a wide class of granular superconductors of the 1:2:3 type, only granular superconductors based on HTSC YBa2Cu3O7-δ can be used as the main material for dissipative-free transfer of electric current at the boiling point of liquid nitrogen.