Bull. Matcr. Sol., Vol. 9, No. 4, No~cmbcl !987, pp. 203 201. ¢' Printed m India. Aiiovalent substitution in fl-LizSO 4 towards conductivity enhancement K SINGH, S S BHOGA and F C RAGHUWANSHI Department of Physics, Nagpur University, Nagpur 440 010, India MS received 25 May 1987: revised 20 July 1987 Abstract. Aliovalent sulphates were selected for substitution in fl-LiESO4 at 6."/o vacancy concentration. The results show that if the guest ions are substituted on the basis of the criteria given for the formation of a solid solution, lhen it is possible to achieve a consider- able enhancement in conductivity especially in the case of isostructural materials. Keywords. Aliovaten! substitulion: conduclivily enhancement. I. Introduction Solid electrolytes have attracted attention due to their potential use in several technical applications. The prospects for developing an ideal solid electrolyte are good and it is necessary to determine the conditions of the atomic arrangement for this purpose. The sulphate-based solid electrolytes differ in some respects from the other solid electrolyte materials. An advantage is that many mono- and divalent cations have high mobility in them and thus increasing the choice of anode material in power sources (Heed et al 1975). Amongst all the sulphates studied so far, lithium sulphate is a well-studied solid electrolyte (Benrath and Drekopf 1921; Kvist and Lunden 1965; Kvist 1966, 1967; Heed et al 1977). It undergoes a phase transition from a monoclinic to cubic structure at 848 K. Its high temperature form has very high ionic conductivity, comparable to the molten salts (Kvist and Lunden 1965). The effect on the ionic conductivity of substitution of divalent cations Mg 2+, Ca 2+ and Zn 2+ for Li + in the high temperature form of LiESO 4 has been investigated (Heed et al 1977). Monoclinic Li2SO 4 has low electrical conductivity at ambient temperatures. Its electrical conductivity has been studied in the monoclinic phase from 550 K to 848 K (Deshpande and Singh 1982). According to Kimura and Greenblatt (1984), an addition of small quantity of trivalent sulphate enhances the conductivity of fl-Li2SO 4. Similar effect has been reported in NazSO 4 (Murray and Secco 1978; H6fer and Esyel 1981; Saito et al 1984) and KzSO 4 (Natarajan and Secco 1975). The maximum conductivity was obtained for 7°/o vacancy concentration for Na2SO4 (H6fer and Esyel 1981). Using the same concept, different vacancy concentrations were calculated for fl-Li2SO 4. In the present investigation, the effect on the ionic conductivity of the partial substitution of Li + by divalent calions Ca 2+, Ba 2+ and Mg 2+ in /~-LieSO 4 has been studied to determine whether such a replacement would enhance the ionic conductivity, as a result of the increased vacancies in the cation subtattice described by Li aaz + LqxSO,~. 2 -2x~Wtx 263