Effect of In-doping on the microstructure and CH4-sensing ability of porous CaZrO3/MgO composites

Porous In-doped CaZrO3/MgO composites (nominally, CaZr0.95In0.05O2.975/MgO and CaZr0.90In0.10O2.95/MgO) were prepared by pressureless reactive sintering of CaMg(CO3)2, ZrO2 and In2O3 with 0.5 mass% LiF additive. The In-doped composites had a uniform open-porous microstructure, similarly to the porous CaZrO3/MgO composites as reported before, but their pore-size became slightly larger. The CH4-sensing properties both in argon and air atmospheres were investigated at 600–900 °C. It was found that the In-doping was effective to increase the CH4-sensitibity in air for all temperature range, whereas it decreased the CH4-sensitibity in argon. These results can be qualitatively explained by the increase in oxygen vacancies induced by the In-doping.