The whole region of superconductivity in the Ba1-xKxBiO3 (BKBO) system (0.35 < x < 1) has been investigated by synthesizing the samples with the high pressure and high temperature technique. As the K doping ratio (x) increases, the superconducting transition temperature (Tc) 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 Tc 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 Tc by doping in the cubic BKBO system is compared with other superconducting bismuthates and discussed on a basis of its electronic band structure.
- High pressure and high temperature technique