MAGNETIC AND SUPERCONDUCTING PROPERTIES OF Fe-DOPED HIGH-TEMPERATURE SUPERCONDUCTORS YBaCuO SYNTHESIZED BY SOL-GEL METHOD

For a series of iron-doped polycrystalline high-temperature superconductors Y_1–xFe_xBa₂Cu₃O_y (0 ≤ x ≤ 0.05), synthesized using the nitrate-citrate variant of the sol-gel method, studies of structural (by X-ray and electron microscopy methods) and magnetic (in alternating and constant magnetic fields) properties were conducted. For these samples, the dependencies of crystallographic parameters, crystallite sizes, superconducting transition temperatures on the doping level were determined, as well as the type and magnitude of magnetization hysteresis in fields up to 6 T. Field dependencies of intracrystalline critical current density Jc were calculated. It was shown that uniform distribution of the dopant throughout the crystallite volume due to the application of the sol-gel method leads to significant improvement in functional parameters compared to samples obtained by solid-state method. The microstructure improves, which is manifested in increased sizes and more distinct crystallite faceting, as well as narrowing of the temperature interval of transition to the superconducting state, increase in the magnitude of magnetic field hysteresis of magnetization and critical current. As a result, in sol-gel samples with iron doping level x ≈ 0.03, an increase effect Jc exceeding an order of magnitude is achieved.