Analysis of chemical ordering and fragility for Ge–Se–In glasses

Abstract

Decreasing the band gap of a material due to metal impurities has been approved through several studies, and this subject is considered as a major area of interest within the optoelectronic applications. Indium-based chalcogenides have been considered good candidates in nonlinear optics due to their ability to transmit in the infrared region. Hence, Ge18Se82 has been alloyed with In. The nature of the chemical ordering of amorphous samples of Ge18Se82-xInx (x = 0, 2, 4 and 6) have been systematically studied. The aim of present investigation is to understand the role of chemical composition and meancoordination number in determining their structural and physical properties. The compactness, d, of alloyed samples has been calculated from their measured densities, and values obtained have been interpreted using the topological model proposed to describe the atomic arrangements in these alloys. The variation of the glass transition temperature, Tg, with the average coordination number, Z, has been investigated. The compositional dependence of the mean atomic volume, Vm, has also been determined. The free volume percentage, FVP, in Ge18Se82-xInx amorphous samples and their fragility indices, m, have been determined to examine the relationship with the mean-coordination number. We have also analyzed the obtained results on the basis of average single bond energy and electronegativity.