Electrical conductivity of (Na₃AlF₆-40%K₃AlF₆)-AlF₃-Al₂O₃ melts

Abstract

The effects of contents of AlF₃ and Al₂O₃, and temperature on electrical conductivity of (Na₃AlF₆-40%K₃AlF₆)-AlF₃-Al₂O₃ were studied by continuously varying cell constant (CVCC) technique. The results show that the conductivities of melts increase with the increase of temperature, but by different extents. Every increasing 10 °C results in an increase of 1.85×10⁻², 1.86×10⁻², 1.89×10⁻² and 2.20×10⁻² S/cm in conductivity for the (Na₃AlF₆-40%K₃AlF₆)-AlF₃ melts containing 0%, 20%, 24%, and 30% AlF₃, respectively. An increase of every 10 °C in temperature results an increase about 1.89×10⁻², 1.94×10⁻², 1.95×10⁻², 1.99×10⁻² and 2.10×10⁻² S/cm for (Na₃AlF₆-40%K₃AlF₆)-AlF₃-Al₂O₃ melts containing 0%, 1%, 2%, 3% and 4% Al₂O₃, respectively. The activation energy of conductance was calculated based on Arrhenius equation. Every increasing 1% of AlF₃ results in a decrease of 0.019 and 0.020 S/cm in conductivity for (Na₃AlF₆-40%K₃AlF₆)-AlF₃ melts at 900 and 1 000 °C, respectively. Every increase of 1% Al₂O₃ results in a decrease of 0.07 S/cm in conductivity for (Na₃AlF₆-40%K₃AlF₆)-AlF₃-Al₂O₃ melts. The activation energy of conductance increases with the increase in content of AlF₃ and Al₂O₃.

Keywords

aluminum electrolysis / electrical conductivity / activation energy / additive / superheat

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