PHOTOCHROMIC MATERIAL COMPRISING RARE EARTH ION ADDED ALKALI HALIDE CRYSTAL

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PROBLEM TO BE SOLVED : To provide an inorganic substance which reversibly causes a photochromic phenomenon upon irradiation with light in a visible region at room temperature.SOLUTION : A great number of lattice defects are produced in rare earth ion added alkali halide crystals, whereby electrons of rare earth ions can easily be released to many neighbor lattice defects even by light excitation which does not reach a conduction band of the base. When the released electrons are captured by the lattice defects, a color center is formed. If a great number of such color centers are formed, these can be observed as variation of an absorption spectrum.COPYRIGHT : (C)2006, JPO&NCIPI