Evidence for Superconductivity Above 20K in the Ba-K-Bi-O System.

TOP 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 s (x approx 0.2) provide evidence for superconductivity above 20K in a minority fraction (~ 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-x) Bi sub x O sub s 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 ~ 22K vs. 13K) superconducting transition temperatures.