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 absorbance band at 390 to 400nm was introduced into 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 aluminum doping suppresses the band formation induced by grinding; however, the doping did not suppress the band formation induced by heat treatment.

Effects of Aluminum Doping upon Color Formation in Zinc Oxide Powders. Rafla‐Yuan, H., Cordaro, J.F.: Journal of Applied Physics, 1993, 74[7], 4685