Novel (La0.2Eu0.2Nd0.2Sm0.2Pr0.2)(Al0.6Co0.4)O3-δ and (La0.2Eu0.2Nd0.2Sm0.2Ca0.2)(Al0.6Co0.4)O3-δ high-entropy ceramics with high emissivity and low degradation

Novel (La0.2Eu0.2Nd0.2Sm0.2Pr0.2)(Al0.6Co0.4)O3-δ (HE-1) and (La0.2Eu0.2Nd0.2Sm0.2Ca0.2)(Al0.6Co0.4)O3-δ (HE-2) high-entropy ceramics were synthesized via solid-phase reaction technology. These two ceramics simultaneously own excellent infrared radiation performance and low degradation. The mechanism of emissivity enhancement was investigated, and emissivity decay of ceramics heated at 1500 °C for various holding time was studied. The results verify that the synthesized ceramics have perovskite crystal structure. The emissivity values of HE-1 and HE-2 are 0.78/0.66 and 0.82/0.83 in the near/mid-infrared band, respectively. These IR emissivity values are much higher than that of pure LaAlO3, which is attributed to enhanced impurity absorption, free carrier absorption and lattice vibration absorption. Moreover, after heating at 1500 °C for 10 h, HE-1 and HE-2 ceramics appear extremely slower emissivity decay rate (1.2–4.5 %), in comparison with fast decay rate (25.5–36.8 %) of pure LaAlO3. This phenomenon can be attributed to the hysteresis diffusion effect of high-entropy ceramics, which can inhibit grain growth and emissivity decay. The novel ceramics have important application prospect in long-term energy-saving for high-temperature industry.