Photochromic effect in Fe-doped PLZT ceramics

The photochromic effect in Fe-doped transparent PLZT ceramics was investigated. The ceramics are darkened by irradiation with blue light having a wavelength of less than 4800 A. The induced dark state is stable at room temperature and can easily be bleached back to its original transparent state by heat treatment at approximately 2000C. The photoinduced optical density change depends strongly on the transparency of the ceramic. Response times for the darkening and bleaching were investigated as a function of the excitation light intensity and the temperature of the ceramic. A tentative model explaining the observed effect is proposed, and the photochromic mechanism is discussed on the basis of a charge-transfer process between the photoactivated Fe3+ and Fe4+ impurities in the ceramic. 8 fig