A consistent approach towards Bi doping mechanism in chalcogenide glasses from Cp measurement in Ge-Se-Te-Bi system

In this paper, we are proposing a consistent approach to understand the mechanism of Bi doping in Ge-Se glasses by carrying out specific heat (C-p) measurement in Ge20Se70-xTe10Bix system for 0 less than or equal to x less than or equal to 11. The two softening temperatures exhibited by heat-treated samples are explained on the basis of 'microscopic phase separation'. The minimum in 'configurational heat capacity' (Delta C-p) at x = 7.5 for as-prepared glasses is related to be a feature of chemical threshold. A supporting evidence for three-fold coordination for Bi in line with the earlier structural studies is deduced. (C) 2000 Elsevier Science Ltd. All rights reserved.