OPTICAL-PROPERTIES OF TRANSPARENT GLASS-CERAMICS IN K2O-NB2O5-TEO2 GLASSES

Transparent glass-ceramics consisting of a cubic crystalline phase with crystallites having diameters between 20 and 40 nm in the composition of 15K(2)O-15Nb(2)O(5)-70TeO(2) (mol%) have been fabricated. A phase with cubic structure is formed by post-heat-treatment at around 390 degrees C for 1 h and transforms into a stable phase at temperatures above 450 degrees C. The glass-ceramics consisting of a stable crystalline phase are opaque. The transparency of glass-ceramics is attributed to a small particle size (average radius: 10-20 nm) of the cubic crystalline phase. The optical and dielectric properties for the transparent glass-ceramics obtained by heat-treatment at 425 degrees C for 1 h are: refractive index, n = 2.11 +/- 0.02; relative permittivity (1 kHz, 300 K), epsilon(r) = 44 +/- 1 and third-order non-linear optical susceptibility, chi((3)) = 3.3 X 10(-13) esu. These values are larger than those for the original base glass, i.e. n = 2.02 +/- 0.02, epsilon(r) = 28 +/- 1 and chi((3)) = 0.9 X 10(-13) esu. Second-harmonic generation is clearly observed in transparent glass-ceramics. These transparent glass-ceramics have a potential as a new type of non-linear optical material.