PREPARATION AND CHARACTERIZATION OF GLASSES IN THE BISMUTH CHLORIDE - POTASSIUM CHLORIDE SYSTEM (HALIDE, INFRARED, VISCOSITY)
Abstract
Glasses ranging in composition from 20 KCl 80 BiCl(,3) to 45 KCl 55 BiCl(,3) have been prepared and their properties studied. The preparation must be done under chlorine to avoid forming reduced species of bismuth which give a bright red color to the glass. The glass transition temperatures range from 15(DEGREES)C for the 20 KCl 80BiCl(,3) glass to 45(DEGREES)C for the 45 KCl 55 BiCl(,3) glass. The addition of modifiers only raises the glass transition temperature slightly, giving the highest T(,g) of 57(DEGREES)C for the composition of 49 BiCl(,3) 40 KCl 11 PbCl(,2). The optical properties of these glasses are quite exceptional. The infrared cutoff is at 14 (mu)m, and the uv cutoff is at 400 nm. The stimulated emission cross section for the ('4)F(,3/2) (--->) ('4)I(,11/2) transition is 6.25 x 10('-20) cm('2). The refractive indices are extremely high, around 1.9 for the chlorides and ranging up to 2.2 for the bromide analogs. The behavior of the molten mixtures is characteristic of the behavior of fragile liquids. The viscosity behaves in a strongly non-Arrhenius fashion in the intermediate range of temperatures, but becomes Arrhenius at high temperatures and at temperatures near the glass transition temperature. The viscosity can be fit fairly well by the Vogel-Tamman-Fulcher equation. The liquid behavior is very similar to that of other ionic glass formers such as in the Ca(NO(,3))(,2)-KNO(,3) system. The change in heat capacity at the glass transition temperature is quite large, ranging from 3.5 to 4.0 cal g-atom('-1) K('-1). The glass heat capacities are near the classical limit of 3R. The entropy of fusion for the compound at .33 KCl .67 BiCl(,3) is 5.17 e.u. mol('-1). The Kauzmann temperature for this composition is 282 K. This is below the value of T(,o) obtained from the VTF fit, as is usually observed in the fragile liquid systems.
Degree
Ph.D.
Subject Area
Chemistry
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