气相分压对Co-Fe-Sb三元体系相平衡和相稳定性的影响

Effect of gas phase pressure on phase stability and phase equilibrium of Co-Fe-Sb ternary system

通过真空条件下Co-Fe-Sb三元体系1 073 K等温截面测定、Co-Fe-Sb三元体系凝聚态的热力学优化评估和气相组分的热力学数据计算,分析气相压力对该体系中二元和三元体系的相平衡和相稳定性的影响。结果表明:随着气相压力减小到一定程度,Co-Sb、Co-Fe、Fe-Sb和Co-Fe-Sb体系中的固相化合物相开始发生挥发分解,出现气液固三相平衡区,计算所得温度—压力曲线图表明每种化合物相都存在一个理论的压力极小值,并对应一个温度,在此压力之上或温度以下,不发生化合物由固相转变成气相的分解,凝聚态相保持与常压下基本相同的相平衡关系。计算结果从热力学上很好地解释了含Sb热电材料在试验研究和材料制备过程中存在的问题,对制备该化合物的工艺设计具有很好的参考作用。

By means of the determination of the isothermal-section at 1 073 K of the Co-Fe-Sb ternary system in vacuum condition,the assessed thermodynamic parameters of the condensed phases and those of the constituent gas-phase species of the Co-Fe-Sb ternary system,the influences of the gas-phase pressure on the phase equilibria and the phase stability of the binary and ternary systems were calculated and analyzed.The results show that the compounds of the Co-Sb,Co-Fe, Fe-Sb and Co-Fe-Sb systems start to pyrolyze when the gas-phase pressure decreases to a certain degree,and the gas-liquid-solid three-phase equilibrium zones appear.The calculated pressure—temperature curves show that each compound has a minimum pressure value corresponding to a temperature for its decomposition or pyrolysis.Above the minimum pressure or below the temperature,the compound phase cannot decompose from solid phase to gas phase with temperature change and can keep the same phase relations as those at the normal pressure.The calculated results can thermodynamically explain the problems appearing in the experimental investigations and the preparation processes of the Sb containing thermoelectric materials,and can be helpful for reference to the process design for the preparation of the compound.