Transmission electron microscopy studies of 70Ga(2)S(3)-30La(2)S(3) glasses

The crystallisation of 70Ga(2)S(3)-30La(2)S(3) samples after isothermal reh eating for 3 h just above the glass transformation range (T-g), and then qu enching to ambient, has been studied using transmission electron microscopy (TEM). Glasses prepared from sulphides were melted under vacuum in a vitre ous carbon crucible, sealed inside a silica tube. Those samples with the sm allest oxide content showed evidence of devitrification on quenching. On re heating to similar to T-g,T- barrel-shaped crystallites were observed that were composed of laths of a new monoclinic phase, with Ga-rich inter-lath c rystal, presumed to be Ga2S3. On reheating glass samples containing greater amounts of oxide, barrel shaped crystals formed whose internal microstruct ure was composed of laths of tetragonal La3.33Ga6S14 and the new monoclinic phase in a eutectic or eutectoid-like configuration. (C) 1999 Published by Elsevier Science B.V. All rights reserved.