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通过热力学计算B-Mg B2体系中可能发生化学反应的标准吉布斯自由能变化值(ΔrGθT)随温度变化的关系,对其体系的热稳定性进行了探讨。综合应用X射线衍射、标准四线法和扫描电子显微镜对在氩气气压为103Pa条件下993 K退火10~30 min的B/Mg B2异质结试样的晶体结构、超导电学特性及断面结构进行了测量研究。实验结果表明,B-Mg B2体系在973 K以下温度范围内能保持良好的热稳定性,但随着背景气压降低,Mg B2会发生缓慢分解,使得异质结微观结构和超导特性受到影响。
The thermal stability of standard Gibbs free energy change (ΔrGθT) of B-Mg B2 system with temperature dependence was calculated by thermodynamic calculation. X-ray diffraction, standard four-wire method and scanning electron microscopy were used to study the crystal structure, superconductivity and cross-section of B / Mg B2 heterojunction samples annealed at 993 K for 10-30 min under an argon pressure of 103 Pa The structure was measured. The experimental results show that the B-Mg B2 system can maintain good thermal stability under the temperature range of 973 K, but slowly decomposes with the decrease of the atmospheric pressure and the microstructure and superconductivity of the heterojunction are affected .