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 elect rical conductivity for molten cryolite, for binary mixtures of cryolit e with Al2O3, AlF3, CaF2, KF, Li3AlF6, and MgF2, and for ternary mixtu res Na3AlF6-Al2O3-CaF2 (MgF2) and Na3AlF6-AlF3-KF (Li3AlF6). The cell constant was about 40 cm(-1). The temperature and concentration depend ence of the conductivity in the investigated concentration range was d escribed by the equation kappa/S cm(-1) = 7.22 exp (-1204.3/T)-2.53[Al 2O3]-1.66[AlF3] -0.76[CaF2]-0.206[KF]+0.97[Li3AlF6]-1.07[MgF2] -1.80[A l2O3][CaF2]-2.59[Al2O3][MgF2] -0.942[AlF3][Li3AlF6] where T represents the temperature in Kelvin and the brackets represent the mole fractio ns 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 t he conductivity equation can reach up to 2.5 pet.