Changes in the defect structure, which were caused by heat treatment and laser irradiation, were studied by means of cathodoluminescence scanning electron microscopy. The results were compared with those for untreated and electron-irradiated samples. It was found that annealing of the Bi12GeO20 samples led to the appearance of a new luminescence band at about 390nm. The centers which were responsible for this band decorated the deformation slip-bands in quenched samples, as observed in cathodoluminescence images. An emission which was observed in Bi12SiO20 over the same spectral range was quenched during annealing. An annealing-induced reduction of Bi ions to metallic Bi was suggested to be related to the quenching of a band at 640nm in untreated samples.

A.Cremades, J.Piqueras, A.Remón, J.A.García, M.T.Santos, E.Diéguez: Journal of Applied Physics, 1998, 83[12], 7948-52