Study of amorphous Sn–Se–Bi–Te semiconducting materials at an average coordination number = 2.4

Abstract

Amorphous chalcogenide materials are of great importance owing to their excellent properties in infrared and thermoelectrics. A complex system of (SnSe4)95-x(Bi2Te3)5+x (x = 0, 5, 15, 25, 35, 45 at%) chalcogenide materials have been synthesized. A semi-empirical approach has been employed to study the various physical parameters corresponding to the synthesized samples. All the compositions correspond to an average coordination number 〈r〉 = 2.4. Structural, morphological and elemental studies using XRD, FESEM, and EDS respectively have been performed for all the compositions. The density of the system increases with the addition of Bi2Te3 replacing SnSe4 in the system. The calculations of free volume percentage show an increase with increasing Bi2Te3 content. The semi-empirical energy gap values show a decrease from 1.57 eV to 1.04 eV. This decrease in energy gap values is well supported by a decrease in average single bond energy. The high percentage covalent character above the benchmark supports the glass forming ability. The glass transition temperature is determined from Tichy-Ticha approach and shows an increase with increasing x at%.