Optical and thermal diffusivity measurement of Ge-Se-Te glasses by photoacoustic technique

Abstract

The composition dependence of optical energy gap (E_g) and thermal diffusivity a in three sets of Ge-Se-Te glasses, namely, Ge_xSe_80-xTe₂₀ (5 = x = 40), Ge_xSe_75-xTe₂₅ (5 ≤ x ≤ 40), and Ge_xSe_65-xTe₂₅ (5 ≤ x ≤ 37.5), have been studied using photoacoustic technique. The variation of a with average coordination number <r> shows a change in the slope at <r> = 2.4 and 2.67. E_g shows a local maximum at <r> = 2.67. The results are discussed on the basis of the topological and chemical threshold exhibited by covalent network glasses. The relative sensitivity of a and E_g to these phenomena is discussed.