Research on the sintering temperature and absorptivity of corundum-based endothermic ceramics for solar thermal power generation

The absorptivity of endothermic materials serves as a critical index for solar thermal power photothermal conversion systems, and ceramic-based endothermic materials characterized by high absorptivity also exhibit elevated sintering temperatures. In this study, CaF 2 was employed as an additive to investigate its effects on the physical properties and microstructure of the samples, with a particular focus on the mechanism by which CaF 2 reduces the sintering temperature of corundum-based endothermic ceramics. The results showed that the G2 sample (1 wt% CaF 2 ), sintered at 1650 °C, displayed the best physical properties, including 93 % absorptivity, 165.43 MPa bending strength. The sintering temperature of the CaF 2 -doped G-series samples was around 60 °C lower due to liquid-phase calcium hexaaluminate formation from CaF 2 and Al 2 O 3 , which enhanced atomic migration and facilitated ceramic matrix sintering. Additionally, the capillary forces of the liquid-phase calcium hexaaluminate promoted ceramic matrix shrinkage and accelerated corundum-based grain growth through the dissolution-precipitation mechanism, leading to densification. Moreover, the G2 sample exhibited excellent durability, with absorptivity decreasing by only 1.9 % after 100 h at 1000 °C.