Optical properties of boride ultra-high temperature ceramics for solar thermal absorbers

It is a known rule that the efficiency of thermodynamic solar plants increases with the working temperature. At present the main limit in temperature upscaling is the absorber capability to withstand high temperatures. The ideal solar absorber works at high temperatures and has both a low thermal emissivity and a high absorptivity in the solar spectral range. The present work reports on the preparation and optical characterization of hafnium and zirconium diboride ultra-high-temperature ceramics for novel solar absorbers operating at high temperature. Spectral hemispherical reflectance from the ultraviolet to the mid-infrared wavelength region and hightemperature hemispherical emittance reveal their potential for high-temperature solar applications. Boride samples are compared to silicon carbide (SiC), a material already used in solar furnaces.