The effects of Ca2+ and Y3+ ions co-doping on reducing infrared emissivity of ceria at high temperature

The ceria powders co-doped with Ca2+ and Y3+ ions Ce0.8Y0.2−xCaxO2−δ were prepared by oxalate co-precipitation method. The crystal structure, morphology, conductivity and infrared emissivity of the pure and doped ceria were analyzed in detail. From the perspective of microstructure and conductivity, the reasons for the reduced infrared emissivity in ceria by co-doping Ca2+ and Y3+ ions are revealed. The results show that singe-phased ceria with cubic fluorite structure is obtained in all the samples with Y3+ or/and Ca2+ ions doping. The lattice parameter 'a' of ceria phase increases gradually with Ca2+ ions content increasing from x = 0 to x = 0.2 in the Ce0.8Y0.2−xCaxO2−δ. The grains become smaller and distributed more homogeneously after doping Y3+ or/and Ca2+ ions. The conductivity increases with temperature rising and Y3+ or/and Ca2+ ions doping, in which Ce0.8Y0.2−xCaxO2−δ with x = 0.05 possesses the highest conductivity among all the samples. Contributed by decreased grain aggregation and enhanced conductivity, lowest infrared emissivity value of 0.241 at 600 °C is achieved in the Ce0.8Y0.15Ca0.05O2−δ, which reduces nearly 33% compared to the un-doped ceria. It indicates that Y3+ and Ca2+ ions co-dopant has a decisive effect on reducing infrared emissivity of ceria at high-temperature, which provides an effective and convenient method to develop infrared stealth materials for high-temperature use.