Study of the elastic, opto-electronic and thermoelectric properties of ternary chalcogenides X2Sb2Se5 (X=Ge, Sn)

Abstract

There search on phase change materials in the last decades has extensively been outlined. Fascinating and promising as
these materials and their applications are a profound understanding of the material physics is desire. The chalcogenide
material Ge2Sb2Te5 is the prototype phase-change material. The effect of replacing Ge by Sn et Te by Se was studied for a
systematic understanding and prediction of new potential candidates for PCRAM applications.
The structural, elastic,opto-electronic and thermoelectric properties of Ge2Sb2Se5 and Sn2Sb2Se5 ternary alloys have been
investigated using the full-potential (linearized) augmented plane wave method. To make the results comparably the opto-
electronic calculations, were performed using two methods, namely generalized gradient approximation developed by
Perdew-Burke-Emzerhof (PBE-GGA), and recently developed modified Becke–Johnson (mBJ) potential. This is found to
be a semiconductor with energy band gap equal to 0.64 eV and 0.57 eV for Ge2Sb2Se5 and Sn2Sb2Se5 respectively . All the
elastic constants obey the Born−
Huang criteria, suggesting that they are mechanically stable This material is being reported
as thermoelectric material. The Seebeck coefficient increases with temperature and attains the maximum value 650 V/K
and 580 μ
V/K at T=300 K for Ge2Sb2Se5 and Sn2Sb2Se5 respectively. The material has achieved the maximum value of ZT is
0.92 for Ge2Sb2Se5 and 0.97 for Sn2Sb2Se5 at 300 K.