Coloring zirconium oxide for novel energy saving industrial applications

White conventional zirconium oxide was mixed to black or rust coloring second phase additives to increase the absorptance and thermal emittance with the aim of exploring novel oxide-based ceramics for energy exploitation and saving, like solar absorbers or even industrial refractory kiln walls. The variation of the optical properties of the colored samples was evaluated as a function of the amount, dopant type and co-doping and it was found that notable changes to the optical spectrum occur already upon introduction of 0.05 wt% pigment. The absorptance of ZrO2 passed from 0.1, in the white ceramic, to 0.75, for the rust-colored ones, and up to 0.82, for black colored materials containing Co-oxide as additive. The thermal emittance and solar absorptance of the black/rust-shaded specimens were calculated for temperatures from 400 to 1500 K and compared to commercial white, black and brown reference to identify the most appropriate composition for the two proposed applications and operating temperatures.