Effect of co-doping with calcium and transition metals on the infrared emissivity of La₂(Zr_0.7Ce_0.3)₂O₇ ceramics for high-temperature thermal protection applications

Abstract

The La₂(Zr_0.7Ce_0.3)₂O₇ (LZ7C3) ceramics co-doped with Ca²⁺ and different transition metal cations (Fe³⁺, Cr³⁺) were fabricated by the pressureless-sintering method. The influence of doping on the phase structure, microstructure and infrared emissivity (0.75–2.5, 3–5, 8–14 µm) was investigated. The infrared emissivity of LZ7C3 in the wavelength range 0.75–2.5 and 3–5 µm was significantly enhanced by co-doping, especially with Ca²⁺ and Cr³⁺. The infrared emissivity in the wavelength range 0.75–2.5 µm could be improved from 0.069 (LZ7C3) to 0.876 at room temperature, and from 0.463 (LZ7C3) to 0.877 in 3–5 µm at 300 °C, by co-doping with Ca²⁺ and Cr³⁺. On the other hand, doping had an insignificant effect on the infrared emissivity of LZ7C3 in the 8–14 µm range at 300 °C due to its high emissivity value (0.962) in the 8–14 µm range.