Composition-dependent thermoelectric properties of n-type Bi2Te2.7Se0.3 doped with In4Se3

Abstract

We present the effects of In4Se3 addition on thermoelectric properties of n-type Bi2Te2.7Se0.3. In this study, polycrystalline (In4Se3)x-(Bi2Te2.7Se0.3)1-x pellets were prepared by mechanical alloying followed by spark plasma sintering (SPS). The thermoelectric properties such as Seebeck coefficient and electrical and thermal conductivities were measured in the temperature range of 300 K to 500 K. Addition of In4Se3 into Bi2Te2.7Se0.3 resulted in segregation of In4Se3 phase within Bi2Te2.7Se0.3 matrix. The Seebeck coefficient of the (In4Se3)x- (Bi2Te2.7Se0.3)1-x samples exhibited lower values compared with that of pure Bi2Te2.7Se0.3 phase. This reduction of Seebeck coefficient in n-type (In4Se3)x- (Bi2Te2.7Se0.3)1-x is attributed to the formation of unwanted p-type phases by interdiffusion through the interface between (In4Se3)x and (Bi2Te2.7Se0.3)1-x as well as consequently formed Te-deficient matrix. However, the decrease in electrical resistivity and thermal conductivity with addition of In4Se3 leads to an enhanced thermoelectric figure of merit (ZT) at a temperature range over 450 K: a maximum ZT of 1.0 is achieved for the n-type (In4Se3)0.03-(Bi2- Te2.7Se0.3)0.97 sample at 500 K.