Thermodynamic modeling of the Ge-La binary system

Miao Liu 1, 2) , Chang-rong Li 1) , Zhen-min Du 1) , Cui-ping Guo 1) , and Chun-ju Niu 1) 1) School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China 2) The 3rd Department, Institute of Chemical Defense of PLA, Beijing 102205, China

摘 要：The Ge-La binary system was critically assessed by means of the calculation of phase diagram （CALPHAD） technique. The associate model was used for the liquid phase containing the constituent species Ge, La, Ge 3 La 5 , and Ge 1.7 La. The terminal solid solution diamond-（Ge） with a small solubility of La was described using the substitutional model, in which the excess Gibbs energy was formulated with the Redlich-Kister equation. The compounds with homogeneity ranges, α（Ge 1.7 La）, β（Ge 1.7 La）, and （GeLa）, were modeled using two sublattices as α（Ge,La） 1.7 La, β（Ge,La） 1.7 La, and （Ge,La）（Ge,La）, respectively. The intermediate phases with no solubility ranges, Ge 4 La 5 , Ge 3 La 4 , Ge 3 La 5 , and GeLa 3 , were treated as stoichiometric compounds. The three allotropic modifications of La, dhcp-La, fcc-La, and bcc-La, were kept as pure element phases since no solubility of Ge in La was reported. A set of self-consistent thermodynamic parameters of the Ge-La binary system was obtained. The calculation results agree well with the available experimental data from literatures.

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