Structure and ionic conductivity of ZrO2(MgO)/CaO-Al2O3 bilayer system used as solid electrolyte for sulfur sensor

The ZrO2(MgO)/CaO-Al2O3 bilayer system used as the solid electrolyte for sulfur sensor was fabricated by screen-printing technology using ZrO2(MgO) electrolyte as the substrate and CaO-Al2O3 compounds with different compositions as the coating materials. The effect of the CaO content in the CaO-Al2O3 compounds on the properties of the bilayer systems were investigated in terms of the phase composition, structure and ionic conductivity. It was demonstrated that all the bilayer systems were dense and uniform and a considerable increase in ionic conductivity was observed with increasing temperature and CaO content in CaO-Al2O3 compounds. The increase in total ionic conductivity at the same temperature was mainly attributed to the increase in the grain boundary conductivity. The grain boundary conductivity of the bilayer systems increased exponentially with increasing the CaO content while the total ionic conductivity increased linearly, which could satisfy the requirement of the ion conduction in solid electrolyte for sulfur sensor.