On the theory of superconductivity of ceramic systems

Behaviour of high-temperature superconductors (HTSC) with a higher critical temperature (up to room temperature) in external magnetic field H is studied to optimize HTSC parameters, i.e. upper and lower critical fields Hc2 and Hc1, the results of the study are presented. It is shown that by achieving decrease in the exchange correlation length it is possible to find ways for increasing critical fields. Small exchange correlation length in HTSC and, correspondingly, small length of coherence is caused by covalently bound complexes Cu-O, Bi-O. It is also possible to increase critical parameters of HTSC by using nonsuperconducting sublayer, a layer of superconducting ceramics with high values of spin-phonon coupling being applied to its surface