Electric conductivity in Zn2+-substituted lithium sulfate-alumina ceramics

The ionic conduction mechanism of high-temperature sulfate phases Li2SO4, L iNaSO4, LiAgSO4 and Li4Zn(SO4)(3) has been extensively studied and discusse d for many years. Two mechanisms named as 'paddle-wheel' and 'percolation' mechanisms were presented for ionic migration. In this paper, Zn2+ ion was selected as dopant for Li2SO4 and the transport mechanism is discussed thro ugh the investigation of conductivity change. The results show that the con ductivity of all Zn2+-containing samples is higher than beta -Li2SO4 (Al2O3 ) below 500 degreesC. While above 550 degreesC the samples display higher c onductivity than that of alpha -Li2SO4. However, the conductivity value dec reases first when the amount of Zn2+ is less than 3 mol%, and then increase s and reaches a maximum point around 7 mol% Zn2+ or 7 mol% ionic vacancies. This observation indicates that both paddle-wheel and percolation mechanis ms seem to contribute to the ionic conduction in alpha -Li2SO4. (C) 2000 El sevier Science B.V. All rights reserved.