First Principles investigation of tin telluride Synergistic effect of bismuth and selenium codoping

Abstract

The present thesis focuses on searching for novel newlinethermoelectric materials that can be used across various temperature newlineranges based on first principles study. Lead-free tin chalcogenide newlinematerial is an alternative for thermoelectric devices with suitable band newlinegap, non-toxic and mechanical stability. Due to the appropriate newlineelectronic and atomic structural properties of SnTe, it has been chosen newlinefor further investigation. newlineThe structural, electronic, mechanical, thermal, thermoelectric newlineand optical properties of cubic structured SnTe, SnTe0.875Se0.125, newlineSnTe0.75Se0.25, SnTe0.5Se0.5, SnTe0.25Se0.75, SnTe0.125Se0.875, Sn0.875Bi0.125Te, newlineSn0.75Bi0.25Te, Sn0.5Bi0.5Te, Sn0.25Bi0.75Te, Sn0.125Bi0.875Te, newlineSn0.875Bi0.125Te0.875Se0.125, Sn0.75Bi0.25Te0.75Se0.25, Sn0.5Bi0.5Te0.5Se0.5, newlineSn0.25Bi0.75Te0.25Se0.75, Sn0.125Bi0.875Te0.125Se0.875 and BiTe materials are newlinediscussed at ambient conditions. For accurate electronic structure newlinecalculations, WIEN2k software was used to succeed the DFT based on newlinethe Full-Potential (linearized) Augmented Plane-Wave ((L)APW) newlinemethod. Here the PBE GGA (Perdew-Burke-Ernzerhof-Generalized newlineix newlineGradient Approximation) exchange-correlation potential is used to newlinecalculate the exchange and correlation energy of electrons. For newlineobtaining accurate band gap results we have used the Modified newlineBecke Johnson exchange potential (mBJ) scheme. Due to the presence newlineof f-electron in bismuth, we used Spin-Orbit Coupling (SOC) newlinecalculations for finding electronic and thermoelectric properties of all newlinethe bismuth-based materials. Some works have reported the newlinethermoelectric properties of SnTe and alloys according to our literature newlinereviews. But specifically, there are no theoretical or experimental newlinereports on SnTe that has been co-doped with Bi and Se. For first time newlinewe investigated various physical properties using these elements to newlineproduce an enhanced figure of merit based on first principles newlinecalculations. newlineElastic constants were calculated using optimized lattice newlineparameters of the above-said materials by applying the Morteza Jamal newline