Some physical properties of (Bi2O3)x(BaO)0.5-x(B2O3)0.5 glasses

A series of (Bi2O3)(x)(BaO)(0.5-x)(B2O3)(0.5) glasses were prepared from pure oxides. The glass transition temperature little decreased from 450 to 419 degrees C with the increase in x from 0.2 to 0.4. The coefficient of thermal expansion was found at around 10 +/- 1 ppm C-1, practically independent on x. The structural make-up of the glasses was suggested to be formed by structural groups of BaBi2B4O10 and BiBO3 for 0.25 < x <= 0.5, BaBi2B4O10 and BaB2O4 for x < 0.25 and by BaBi2B4O10 for x = 0.25. The optical band gap was determined in the region 3.35-3.54 eV and the coefficient of the temperature dependence of the optical gap for the temperatures between 30 and 250 degrees C was found nearly constant at around (5.5 +/- 0.5) x 10(-4) eV K-1. The non-linear refractive index of the studied glasses was estimated from the optical gap values at around 0.9 x 10(-11) esu. (C) 2010 Elsevier B.V. All rights reserved.