采用计算相图构建的Ge-Pd体系热力学模型

Thermodynamic Models for Ge-Pd System Using Phase Diagram Calculation

针对Ge-Pd体系实验测定的相图难以外推到多元体系的问题,提出采用计算相图(Calphad)技术构建Ge-Pd体系的热力学模型。Ge-Pd体系中不同类别的相采用不同的热力学模型描述,其中纯组元Ge对Pd几乎不存在固溶度,可直接采用欧洲热力学研究组发布的热力学模型;液相和端际固溶体(Pd)采用溶体模型描述;化学计量比化合物GePd、GePd_2和Ge_8Pd_(21)采用线性化合物模型描述;非化学计量比化合物Ge_9Pd_(25)、GePd_3、α-GePd_5和β-GePd_5采用亚点阵模型描述其成分区间。对于各相的热力学模型参数,利用已有的液相混合焓、液相混合熵、不变反应的温度和成分等实验数据进行优化,获得了Ge-Pd体系中一套自洽的热力学模型。采用该热力学模型的计算结果与大部分实验数据相吻合,可外推至多元体系,从而可为Ge基多元体系的热力学数据库构建、材料成分设计和制备工艺优化提供依据。

Thermodynamic models for Ge-Pd system using calculation of phase diagram （Calphad） are proposed to solve the problem that the experimentally determined Ge-Pd phase diagram is hard to be extrapolated to multi-component system. Different thermodynamic models are employed for different kinds of phases. Because there is no solubility of Pd in pure Ge, Gibbs energy function of pure element from Scientific Group of Thermal Europe is employed for Ge, the solid solution model is used to describe liquid and Pd solid solution, the line compound model is employed to describe stoichiometric phases GePd, GePd2 and GesPd21, and the sublattice model is used for non-stoichiometric phases Ge9Pd25, GePd3, α-GePd5 and β-GePd5. Thermodynamic parameters are optimized by using the experimental data of mixing entropy and enthalpy of liquid, invariant reaction temperature and composition, hence a set of reliable thermodynamic models are obtained. The calculation results based on these models consist with most of experimental data. These models can be extrapolated to multi-component systems, and provide support to the thermodynamic database construction, composition design and preparation optimization of Ge- based multi-component systems.