熔盐法制备Ba1-xKxBiO3超导体及Ba0.6K0.4BiO3的稳定性

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

摘要:

利用熔盐法在260 °C的低温下制备出了单相Ba1-xKxBiO3 (BKBO, 0.315￡x￡0.6)样品。磁性测量结果表明，在x值整个范围内的BKBO样品都表现出超导电性，x=0.4时，超导转变温度达到最高值（Tc=30.6 K）；粉末X射线衍射结果表明，所有样品中均含有少量的BaCO3杂相，它是由于反应过程中Ba(OH) 2·8H2O和空气中的二氧化碳反应造成的；扫描电镜观察BKBO微观形貌为片状。为与熔盐法作比较，利用溶胶-凝胶法制备Ba0.6K0.4BiO3，发现此法难以制备出单相BKBO样品。利用热分析和退火处理来研究熔盐法制备Ba0.6K0.4BiO3的热稳定性，发现样品大约在400 °C开始分解，表明Ba0.6K0.4BiO3在400 °C以上是不稳定的。

Abstract:

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.