Nanocrystallization of rutile and anatase was observed in a CaO- B2 O3 - Bi2 O3 - Al2 O3 -Ti O2 crystallized glass. The color of the present crystallized glass was changed by the heat-treatment temperature, and x-ray diffraction (XRD) patterns of the crystallized glass show that the apparent color change is correlated with the formation of titania nanocrystallites. The particle size of crystallites observed in the transmission electron microscope image is comparable to that measured by XRD pattern. In addition, a large change of refractive index between the rutile particles and glass matrix, 0.8 or larger, was obtained. The present titania crystallized glass will be not only a photocatalytic material but also a promising candidate for random lasing devices.
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