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

Abstract

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 μW/mK2. 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.