PHOTOCHROMIC ABSORPTION IN MOLYBDENUM-DOPED SILLENITES BI12GEO20

The photochromic effect in molybdenum-doped sillenites Bi12GeO20 (BGO) was studied over the temperature range 4-450 K. The broad photochromi c absorption band created under the light illumination could be well a pproximated to a modified Gaussian dependence characteristic of a smal l bound polaron. The kinetics of the photochromic thermal bleaching wa s found to be a temperature activated process. In the limit of the low est temperatures the photochromic absorption, once created, did not de cay during the whole time period of experiment, but it disappeared qui ckly, with a decay time of 6 ms, for temperatures above 350 K. The exp erimental results were analyzed with the aid of non-linear kinetic mod els and the rate constant describing the temperature dependence of the photochromic thermal bleaching was determined.