Thermally stimulated electron delocalization and luminescence quenching of Ce impurities in GdAlO3

A combined photoconductivity and luminescence quenching study, both temperature and spectrally resolved, has revealed the role played by electron delocalization in luminescence quenching of Ce{sup 3+} impurities in the wide band-gap inorganic insulator GdAlO{sub 3}. The anticorrelation found between the temperature behavior of photocurrent and luminescence intensity strongly suggests that luminescence quenching and photoconduction are intimately related by the same process, i.e., thermal stimulated ionization of optically excited Ce{sup 3+} centers: Ce{sup 3+}{yields}Ce{sup 4+}+electron. Quantitative modeling of experimental data using rate equations, however, reveals a 0.05-eV smaller activation energy for luminescence quenching than for photocurrent generation which indicates that quenching predominantly proceeds via the formation of a Ce bound exciton at the originally excited Ce ion. A second quenching process, dominant below 230 K, seems mediated by energy transfer from Ce{sup 3+} via the Gd{sup 3+} sublattice to Ce{sup 4+} centers resulting in hole conductivity via a charge transfer excitation: Ce{sup 4+}{yields}Ce{sup 3+}+hole.