Electrical conductivity of molten cryolite-based mixtures obtained with a tube-type cell made of pyrolytic boron nitride

A pyrolytic boron nitride tube-type cell was used to measure the electrical conductivity for molten cryolite, for binary mixtures of cryolite with Al₂O₃, AlF₃, CaF₂, KF, Li₃AlF₆, and MgF2, and for ternary mixtures Na₃AlF₆-Al₂O₃-CaF₂ (MgF₂) and Na₃AlF₆-AlF₃-KF (Li₃AlF₆). The cell constant was about 40 cm^?t. The temperature and concentration dependence of the conductivity in the investigated concentration range was described by the equation $$\begin{gathered} \kappa /S cm^{ - 1} = 7.22 exp\left( { - 1204.3/T} \right) - 2.53\left {Al_2 O_3 } \right] - 1.66\left {AlF_3 } \right] \hfill \\ - 0.76\left {CaF_2 } \right] - 0.206\left {KF} \right] + 0.97\left {Li_3 AlF_6 } \right] - 1.07\left {MgF_2 } \right] \hfill \\ - 1.80\left {Al_2 O_3 } \right]\left {CaF_2 } \right] - 2.59\left {Al_2 O_3 } \right]\left {MgF_2 } \right] \hfill \\ - 0.942\left {AlF_3 } \right]\left {Li_3 AlF_6 } \right] \hfill \\ \end{gathered} $$ whereT represents the temperature in Kelvin and the brackets represent the mole fractions of the additions. The standard deviation was found to be 0.026 S cm^?1 (～1 pct). For practical reasons, it is often desired to express composition in weight percent. In that case, it holds that $$\begin{gathered} \ln \kappa = 1.977 - 0.0200\left {Al_2 O_3 } \right] - 0.0131\left {AlF_3 } \right] - 0.0060\left {CaF_2 } \right] \hfill \\ - 0.0106\left {MgF_2 } \right] - 0.0019\left {KF} \right] + 0.0121\left {LiF} \right] - 1204.3/T \hfill \\ \end{gathered} $$ whereT represents the temperature in Kelvin and the brackets denote the concentration of the additives in weight percent. However, in this case, the maximum relative error of the conductivity equation can reach up to 2.5 pct.