The glass-forming region in the system TeO2-BaO-TiO2 and the crystalline phases obtained by heat treatment of glasses were examined to fabricate transparent TeO2-based glasses containing ferroelectric BaTiO3 crystals. The glasses containing up to 30mol% BaO and 20mol% TiO2 were obtained. The glass transition temperatures, 341°-463°C, and crystallization temperatures, 463°-589°C, increased with increasing BaO and TiO2 contents. By controlled crystallization, transparent 70TeO2-15BaO-15TiO2 glasses containing BaTiO3 crystals with a diameter of about 5-10μm were successfully prepared. The small difference in the refractive indices, n, between the TeO2-based glass, n=2.1, as matrix and BaTiO3 crystals, n=2.39, leads to transparency, even though the particle size is much larger than the wavelength of visible light.
The Ceramic Society of Japan