Thermodynamic parameters and phonon stability of CdX (X = Te, Se, S): a comparative study

Abstract

This study offers a comprehensive exploration of the thermal characteristics of cadmium chalcogenide (CdX, X = Te, Se, S) compounds. The CdXs are synthesized by mixing high purity precursor elements at elevated temperature under vacuum. The crystalline phases of the samples are investigated through X-ray diffraction (XRD) analysis. The XRD revealed that CdTe exhibits cubic, while CdSe and CdS possess a hexagonal crystalline phase. The thermal properties of CdTe, CdSe, and CdS compounds are determined from the acquired thermogravimetric (TG) and differential thermogravimetric (DTG) analysis. The TG and DTG curves are synchronously acquired for heating rate of 5 K·min⁻¹ in an inert nitrogen atmosphere, for temperature range of ambient to 1248 K. The results of TG analysis reveal that CdTe remains stable up to 965 K, whereas CdSe and CdS exhibit stability beyond 965 K upto 1125 K. The solitary peak in DTG analysis for each samples evident degradation of the samples in one step. The thermal degradation kinetics of all samples is assessed through the application of non-isoconversional Broido, Coats–Redfern, and Piloyan–Novikova relations. The findings from the kinetic parameters corroborate the observed trends in the thermocurves. The outcomes suggest that CdTe undergoes more pronounced weight loss with degradation initiated earlier than CdS and CdSe. The experimental findings about the thermal stability of CdX compounds are reinforced through theoretical investigation into phonon dynamics employing DFT simulations, offering requisite insights into their thermal behaviour.

Graphical abstract