Development of a high temperature conductance cell and electrical conductivity measurements of MAlCl 4 (M = Li,Na and K) melts

Abstract

A high temperature quartz conductance cell with tungsten electrodes was designed and built. Using it, electrical conductivities of three alkali metal tetrachloroaluminates, namely LiAlCl₄, NaAlCl₄ and KAlCl₄, were measured at temperatures up to 800 K. The conductivity values decreased in the order NaAlCl₄>LiAlCl₄>KAlCl₄ and the activation energy for conduction followed the order LiAlCl₄≅NaAlCl₄<KAlCl₄. The conductivity behaviour indicated that alkali metal cations are the predominant charge carrying species in these melts and the conductivity is related to their size dependent mobilities. The anomalous conductivity behaviour of molten LiAlCl₄ in the group was attributed to the small size of the highly polarising Li⁺ cation and some unique structural aspects of the melt. The melting points of LiAlCl₄, NaAlCl₄ and KAlCl₄ were determined to be 421 ± 1, 426 ± 1 and 534 ± 1 K respectively by the conductivity method. It was demonstrated that the conductance cell developed can be used for electrical conductivity measurements of non-volatile molten salts at temperatures up to ∼ 1200 K.

Keywords

HIGH TEMPERATURE MEASUREMENTS ELECTRICAL CONDUCTIVITY MEASUREMENTS MOLTEN SALTS ALKALI METAL TETRACHLOROALUMINATES ION MOBILITY

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