Synthesis and superconductivity properties of Ba1−xKxBiO3

Ba1−xKxBiO3 with x from 0.315 to 0.6 were successfully synthesized by molten salts method and characterized by XRD and magnetic susceptibility measurements. It is found that Ba1−xKxBiO3 powders could directly be precipitated from KOH melts. Superconductivity has been observed in all samples and the highest superconducting transition temperature was found to be Tc = 30.6 K with x = 0.4. The lattice constant linearly depended on the potassium content in accord with the equation of a = 4.3548–0.1743x, and the decrease of the mole ratio of Bi3+/Bi5+ resulted in the increase of the potassium content, which suggested the disproportionation of Bi valence.

► It is found that Ba1–xKxBiO3 powders with x from 0.315 to 0.6 could directly be precipitated from KOH melts.
► Superconductivity has been observed in all samples and the highest was found to be Tc = 30.6 K with x = 0.4.
► It observed that the mole ratio of Bi3+/Bi5+ increased the potassium content, suggesting the disproportionation of Bi valence.