High pressure synthesis and superconductivity of Ba1-xKxBiO3 (0.35 < x < 1)

Abstract The whole region of superconductivity in the Ba 1− x K x BiO 3 (BKBO) system (0.35 x x ) increases, the superconducting transition temperature ( T c ) of the BKBO system decreases from 30.4 K for x =0.37 to very low diamagnetic signal below 3 K for x =0.74. The synthesis of the samples without including any bariums in the starting composition ( x =1) resulted in different T c and lattice parameters from sample to sample with partial substitutions of Bi at the K site in final products. With detailed synthesis information of the BKBO samples which varies with x , the evolution of T c by doping in the cubic BKBO system is compared with other superconducting bismuthates and discussed on a basis of its electronic band structure.