Superconductivity above 20 K in the Ba-K-Bi-O system.

The results of magnetic susceptibility measurements on multiphase Ba-K-Bi-O samples with overall composition Ba/sub 0.9/K/sub x/BiO/sub 3/ (xapprox. =0.2) provide evidence for superconductivity above 20 K in a minority fraction ()similarreverse arrowto)5%) of the sample volume. These results support the expectation that K doping at the inactive Ba donor sites can extend the metallic range of the previously studied BaPb/sub 1/..sqrt../sub x/Bi/sub x/O/sub 3/ alloys closer to the BaBiO/sub 3/ Peierls instability where the strong coupling of the conduction electrons to the O phonons could explain the enhanced (T/sub c/)similarreverse arrowto)22 vs 13 K) superconducting transition temperatures