Phase separation and interface effect in pseudo-quaternary composites of AgxBi0.5Sb1.5-xTe3-x

Abstract

We investigated anisotropic thermoelectric properties of p-type AgxBi0.5Sb1.5- xTe3-x (x = 0.0, 0.1, 0.2 and 0.3) compounds, prepared by melting and hot press sintering. During hot press sintering and annealing process, the eutectoid decomposition of Ag2Te from (Bi,Sb)(2)Te-3 matrix induces intrinsic thermoelectric composites Ag2+delta Te/(Bi, Sb)(2)Te-3. The phase separation increases the phonon scattering which lowered the lattice thermal conductivity. We also found the metallic interfacial layer in a grain boundary from the measurements of conducting atomic force microscopy (AFM) and scanning Seebeck- and scanning thermal-microscopy (SThM). Here we argue that the interfacial conductivity attributes to the increase of power factor due to increase of mobility. Thereby, the phase separation of Ag2Te from the (Bi, Sb)(2)Te-3 matrix gives rise to the enhanced thermoelectric properties at mild-temperature range, resulting in the enhancement of dimensionless thermoelectric figure-of-merit ZT value of 1.02 at 567 K for x = 0.1 along the vertical direction. (C) 2017 Elsevier B. V. All rights reserved.