Effect of NiTe Nanoinclusions on Thermoelectric Properties of Bi2Te3

Abstract

Metal nanoinclusions in bulk thermoelectric matrix create metal–semiconductor interfaces, which can result in improvement in the thermoelectric power factor due to low-energy electron filtering and a simultaneous reduction in lattice thermal conductivity due to increased phonon scattering at grain boundaries. The combined effect results in enhancement of the thermoelectric figure of merit. We report the effect of NiTe nanoinclusions in a Bi2Te3 matrix. The Bi2Te3/NiTe nanocomposite was synthesized by planetary ball milling. Different volume fractions of NiTe nanoinclusions were incorporated into the bulk (Bi2Te3) matrix and uniaxially hot pressed at 100 MPa and 500°C. The presence of nanoinclusions was confirmed by x-ray diffraction and transmission electron microscopy. The Seebeck coefficient, electrical conductivity, and thermal diffusivity were measured from room temperature to 150°C. The carrier concentration of the matrix (Bi2Te3) and the nanocomposites (NiTe/Bi2Te3) at room temperature were deduced from Hall-effect measurements. Addition of NiTe decreased the carrier concentration, and the power factor increased in the 1 vol.% NiTe/Bi2Te3 compared with inclusion-free Bi2Te3 matrix due to an increase in mobility.