Liquidus Temperatures of System Na_3AlF_6-K_3AlF_6-AlF_3 for Aluminum Electrolysis at Lower Temperature

Liquidus temperatures in the molten salt system Na3AlF6-K3AlF6-AlF3 of interest for aluminum electrolysis were determined by thermal analysis method. The results were presented and an empirical equation describing liquidus temperatures for primary crystallization was derived t=1003.5–0.081×A2.3159–5.87×B0.657–0.024×A2.22×B1.14＋ 0.035×A2.17×B1.084, where t is the liquidus temperature in degree Celsius, A denotes the mass fraction of AlF3 in system Na3AlF6-K3AlF6- AlF3, and B denotes K3AlF6/（Na3AlF6＋K3AlF6 ） in mass（%, the value was defined as KR in this paper）. The composition limitations are 0w（AlF3）30%, and 0KR50%. The isothermal diagram of molten salt system Na3AlF6-K3AlF6-AlF3 was obtained in this composition limitation.