Cathodoluminescence study of europium-doped zirconia and cassiterite powders

The cathodoluminescence spectra of ZrO2:Eu3+ powders of average crystallite size 15-35 nm and SnO2:Eu3+ powders of crystallite size 40-50 nm, obtained after different heat treatments, were studied. The change in the room-temperature cathodoluminescence spectra of EU3+, measured between 400 and 750 nm by 4-15 kV excitation, showed that prolonged heat treatment (24 h/950 degrees C) leads to the formation of noncentrosymmetric Eu3+ sites in both systems. In the ZrO2:Eu3+ systems two Spectrum types were detected, for samples heated at relatively low and high temperatures, respectively. These observations are explained qualitatively by the formation of different configurations of oxygen vacancies in the process of crystal growth under heat treatment. Quantitative cathodoluminescence measurements show an increase of the luminous efficiency of the powders which is connected with particle agglomeration during heat treatment. (C) 1997 Elsevier Science Ltd. All rights reserved.