Synergetic enhancement of power factor and suppression of lattice thermal conductivity via electronic structure modification and nanostructuring on Ni and B co-doped p-type Si-Ge alloy

TL;DR

This study enhances thermoelectric performance of Si-Ge alloys by electronic structure modification and nanostructuring, achieving high power factor and low thermal conductivity, resulting in a ZT of approximately 1.56 at 1000 K.

Contribution

It introduces a combined approach of doping and nanostructuring to significantly improve thermoelectric efficiency of Si-Ge alloys.

Findings

Achieved a Seebeck coefficient of 321 μV/K at 1000 K.

Reduced thermal conductivity to 1.47 W/m·K.

Obtained a ZT value of ~1.56 at 1000 K.

Abstract

For simultaneously achieving the high-power factor and low lattice thermal conductivity of Si-Ge based thermoelectric materials, we employed, in this study, constructively modifying the electronic structure near the chemical potential and nano-structuring by low temperature and high-pressure sintering on nano-crystalline powders. Nickel was doped to create the impurity states near the edge of the valence band for enhancing the power factor with boron for tuning the carrier concentration. The nanostructured samples with the nominal composition of Si0.65-xGe0.32Ni0.03Bx (x = 0.01, 0.02, 0.03, and 0.04) were synthesized by the mechanical alloying followed low-temperature and high-pressure sintering process. A large magnitude of Seebeck coefficient reaching 321 {\mu}VK-1 together with a small electrical resistivity of 4.49 m{\Omega}cm, leads to a large power factor of 2.3 Wm-1K-2 at 1000 K. With successfully reduced thermal conductivity down to 1.47 Wm-1K-1, a large value of ZT ~1.56 was obtained for Si0.65-xGe0.32Ni0.03B0.03 at 1000 K