Potassium ion conduction in K2O·(5 − x) Ga2O3· xAl2O3

Abstract

Potassium gallate in which gallium ions are partially substituted by aluminium, K 2 O·(5 − x) Ga 2 O 3· xAl 2 O 3, has been prepared by sintering a mixture of K 2CO 3, Ga 2O 3, Al 2O 3 at 1500°C. It was found from X-ray diffraction that the gallate had the beta-alumina type β phase and that solid solutions were formed on substituting Ga by Al. The potassium gallate thus obtained was revealed to be a relatively high potassium ion conductor by a.c. conductivity and ionic transport number measurements. The potassium ion conductivity decreases monotonically with the aluminium content. In order to analyze the decreasing behavior of the conductivity isotherm, the slot width was calculated from the lattice parameters and the apparent porosity was evaluated using the apparent and theoretical densities. The change of the potassium ion conductivity with the substituted amount of aluminium was explained well by the variation of the slot width.