CATHODOLUMINESCENCE STUDY OF EUROPIUM-DOPED ZIRCONIA AND CASSITERITE POWDERS

The cathodoluminescence spectra of ZrO2:Eu3+ powders of average crysta llite size 15-35 nm and SnO2:Eu3+ powders of crystallite size 40-50 nm , obtained after different heat treatments, were studied. The change i n the room-temperature cathodoluminescence spectra of EU3+, measured b etween 400 and 750 nm by 4-15 kV excitation, showed that prolonged hea t treatment (24 h/950 degrees C) leads to the formation of noncentrosy mmetric Eu3+ sites in both systems. In the ZrO2:Eu3+ systems two Spect rum types were detected, for samples heated at relatively low and high temperatures, respectively. These observations are explained qualitat ively by the formation of different configurations of oxygen vacancies in the process of crystal growth under heat treatment. Quantitative c athodoluminescence measurements show an increase of the luminous effic iency of the powders which is connected with particle agglomeration du ring heat treatment. (C) 1997 Elsevier Science Ltd. All rights reserve d.