Photo-Induced Phenomena in Bi4-xLaxTi3O12

Two photo-induced phenomena have been newly discovered in Bi4-xLaxTi3O12 (BLT0.41). One of them is "photo-darkening phenomenon (PD)"; the laser illuminated area turns black below T = 390 degrees C, where the wavelength of the laser is 514.5 nm. The other is "photo-erasable memory phenomenon (PEM)"; the blackened area produced by the PD becomes transparent when the same laser is illuminated on the other area where is d = 80 mu m away from the blackened area. The PEM is found to occur in the temperature range between 230 degrees C and 390 degrees C in case of d = 80 mu m and in the distance range of d <100 mm at T = 250 degrees C. Since these phenomena do not occur in pure Bi4Ti3O12, the La3+ ions must play an important role.