Effects of transition metal element doping on the structural and thermoelectric properties of n-type Bi2-xAgxSe3 alloys

In this work, it is demonstrated that a higher electrical conductivity can be obtained when Ag atoms, as a transition metal, replaces Bi atoms in the n-type Bi2-xAgxSe3 system. As a result of differences in the atomic mass and size between Ag and Bi, larger Seebeck coefficient is obtained. The concerned Bi2-xAgxSe3 alloys were prepared by melting in high temperature. Identifications of the microstructure and surface morphology were carried out via X-ray diffraction (XRD) analysis and scanning electron microscope (SEM) attached with the energy dispersive x-ray (EDX) unit. All samples are polycrystalline. Seebeck coefficient, electrical and thermal conductivities were measured over the temperature range 300-473K. Notable enhancement in the electrical conductivity is obtained. The thermoelectric power factor is calculated showing its maximum value at 260 mu W/mK(2). High electrical conductivity and high Seebeck coefficient of some of the doped alloys resulted in a promising figure of merit (ZT). The largest ZT is calculated at 0.23 at 473K for the Bi1.8Ag0.20Se3 sample. (C) 2020 Elsevier B.V. All rights reserved.