The Co-Sb-Ga System: Isoplethal Section and Thermodynamic Modeling
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The Co-Sb-Ga ternary system is an important thermoelectric material system, and its phase equilibria are in need of further understanding. The CoSb3-GaSb isoplethal section is experimentally determined in this study. Phase equilibria of the ternary Co-Sb-Ga system are assessed, and the system’s thermodynamic models are developed. In addition to the terminal phases and liquid phase, there are six binary intermediate phases and a ternary Co3Sb2Ga4 phase. The Ga solution in the CoSb3 compound is described by a dual-site occupation (GaVF) x Co4Sb12−x/2(GaSb) x/2 model. Phase diagrams are calculated using the developed thermodynamic models, and a reaction scheme is proposed based on the calculation results. The calculated results are in good agreement with the experimentally determined phase diagrams, including the CoSb3-GaSb isoplethal section, the liquidus projection, and an isothermal section at 923 K (650 °C). The dual-site occupation (GaVF) x Co4Sb12−x/2(GaSb) x/2 model gives good descriptions of both phase equilibria and thermoelectric properties of the CoSb3 phase with Ga doping.
KeywordsIsothermal Section GaSb Thermoelectric Property CoSb Liquidus Projection
The authors acknowledge the financial supports of the National Science Council of Taiwan (NSC101-3113-P-008-001 and NSC102-2221-E-259 -034).
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