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

The ionic conduction mechanism of high-temperature sulfate phases Li2SO4, LiNaSO4, LiAgSO4 and Li4Zn(SO4)3 has been extensively studied and discussed 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 through the investigation of conductivity change. The results show that the conductivity of all Zn2+-containing samples is higher than β-Li2SO4 (Al2O3) below 500°C. While above 550°C the samples display higher conductivity than that of α-Li2SO4. However, the conductivity value decreases first when the amount of Zn2+ is less than 4 mol%, and then increases and reaches a maximum point around 7 mol% Zn2+ or 7 mol% ionic vacancies. This observation indicates that both paddle-wheel and percolation mechanisms seem to contribute to the ionic conduction in α-Li2SO4.