Abstract: The chemical reactivity of Ba-K-Bi-O(BKBO) superconductor with various solutions including water,acid,alkali and organic solvents has been investigated systematically.Results show that BKBO has a strong reaction with HCl acid,a mild reaction with alkali and a very weak reaction with pure water.BKBO almost does not react with organic solvents.Protective layers of polypyrrole(PPy) and polythiophene(PTh) have been prepared electrochemically on BKBO films respectively.Magnetic measurements for PPy/BKBO and PTh/BKBO composites show that the electrochemical process does not degrade the superconductivity of BKBO. Results of wet experiments and magnetic susceptibility measurements show that the PPy layer is able to protect BKBO against acid.

Key words: Ba-K-Bi-O superconductor, polypyrrole, polythiophene, chemical stability