MEAN ATOMIC VOLUME, T-G AND ELECTRICAL-CONDUCTIVITY OF CU-X(AS0.4TE0.6)(100-X) GLASSES

Results of measurements of the mean atomic volume (V), the glass trans ition temperature (T-g) and the electrical conductivity (sigma) on 12 compositions of the Cu-x(As0.4Te0.6)(100-x) glasses, with x from 0 to 20 at.%, are reported and discussed. A reduction in V and a constancy of T-g, are observed as Cu varies from 0 to 3 at.%. To this stage, the Cu atoms occupy interlayer positions in the layered network of the pa rent As0.4Te0.6 glass. The sigma of glasses with less than or equal to 3 at.% of Cu, are less than that of the parent glass. For Cu > 3 at.% , Cu forms bonds with Te and the glasses become regular three componen t As-Te-Cu glasses. Due to this bonding, changes in slope occur in the V as a function of composition and T-g as a function of composition a t Cu content of 3 at.%. The results are examined using a model which e nvisages the formation of Cu2Te, As2Te3 and As structural units in the se glasses. For Cu > 3 at.%, a decrease of the conductivity activation energy and an increase of sigma occur with increasing Cu content. (C) 1998 Published by Elsevier Science B.V. All rights reserved.