Effect of Molar Ratio of Ca²⁺ and Co²⁺ on Infrared Radiation Properties of Co-doped LaAlO₃ Ceramics

n(Ca²⁺)/n(Co²⁺)(n is mole) co-doped LaAlO₃ ceramics were synthesized by a solid-phase reaction technique. The effect of n(Ca²⁺)/nCo²⁺ doping ratio on the infrared radiation performance of LaAlO₃ ceramics (La_1–xCa_xAl_0.8Co_0.2O₃, 0.25≤n(Ca²⁺)/n(Co²⁺)≤2.00) was investigated, and the mechanism for improving infrared radiation property was analyzed. The result reveals that n(Ca²⁺)/n(Co²⁺) co-doped LaAlO₃ ceramics have a perovskite crystal structure. Increasing the doping ratio (0.25≤n(Ca²⁺)/n(Co²⁺)≤1.00) improves the emissivity in the wavelength range of 0.76–2.50 μm. The ceramic specimen with n(Ca²⁺)/n(Co²⁺) of 1.00 (La_0.8Ca_0.2Al_0.8Co_0.2O₃) has the maximum average emissivity (0.87). In the 2.50–14.0 μm band, the average emissivity of all n(Ca²⁺)/n(Co²⁺) co-doped LaAlO₃ ceramics is generally greater than 0.94. The improvement of emissivity can be attributed to the enhancement of free carrier absorption, impurity absorption and lattice vibration absorption. This novel infrared ceramic with a high emissivity has promising prospects for energy-saving applications of thermal equipment.