Effects of aluminum doping upon color formation in zinc oxide powders

Abstract
The effects on the reflectance spectra of zinc oxide powders, of heat treatment, and of mechanical grinding were investigated for both undoped and aluminum‐doped ZnO. A broad absorptance band at 390–400 nm was induced in the undoped powders both by heating in air and by grinding. From a comparison with electron paramagnetic resonance data from the literature, the band could be related to oxygen vacancies. It was found that aluminumdoping suppresses the band formation induced by grinding; however, the doping does not suppress the band formation induced by heat treatment.