Preparation of Ba1−xKxBiO3 by Molten Salt Method and Thermostability of Ba0.6K0.4BiO3

Ba1-xKxBiO3 (BKBO) samples with 0.315≤x≤0.6 were synthesized at a relatively low temperature of 260 °C by molten salt method. The superconductivity was tested in the whole range of x value, the highest superconducting transition temperature Tc = 30.6 K at x = 0.4. X-ray Diffraction patterns reveal that small amount of impurity phase of BaCO3 were detected in BKBO which is attributed to the reactions between Ba(OH)2·8H2O and CO2 in air. The plate-like morphology of BKBO was observed from SEM images. For comparison, sol-gel method was also used in synthesizing Ba0.6K0.4BiO3 sample, but no single phase of BKBO was obtained. For the sample of Ba0.6K0.4BiO3 prepared by molten salt method, the thermostability was investigated by thermo-gravimetric analysis (TGA) and annealing treatment, and the sample was decomposed at 400 °C. The result showed that Ba0.6K0.4BiO3 was thermally unstable above 400 °C.