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(-1). The temperature and concentration dependence of the conductivity in the investigated concentration range was described by the equation kappa/S cm(-1) = 7.22 exp (-1204.3/T)-2.53[Al2O3]-1.66[AlF3] -0.76[CaF2]-0.206[KF]+0.97[Li3AlF6]-1.07[MgF2] -1.80[Al2O3][CaF2]-2.59[Al2O3][MgF2] -0.942[AlF3][Li3AlF6] where T 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) (similar to 1 pet). For practical reasons, it is often desired to express composition in weight percent. In that case, it holds that In kappa = 1.977-0.0200[Al2O3]-0.0131[AlF3]-0.0060 [CaF2] -0.0106 [MgF2]-0.0019[KF]+0.0121[LiF]-1204.3/T where T 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 pet.