Improving thermoelectric properties of bulk Si by dispersing VSi2 nanoparticles

In order to enhance the thermoelectric properties of Si-based bulk materials, the lattice thermal conductivity (kappa(lat)) should be reduced with little degradation of the electrical properties. Our group had previously demonstrated that the phosphorus (P)-rich nanoscale precipitates formed naturally in heavily P-doped bulk Si scatter phonons more effectively than carriers, resulting in a high figure of merit (ZT) [A. Yusufu et al., Nanoscale 6, 13921 (2014)]. Here, we successfully prepared heavily P-doped bulk Si containing metallic VSi2 nanoparticles through the ball milling of Si, V, and P and subsequent spark plasma sintering. The VSi2 nanoparticles did not affect the electrical properties of Si significantly but greatly decreased the kappa(lat), leading to a marked increase in ZT. The maximum ZT value, which was 0.4, was obtained at 1073 K, which is two times higher than that for Si. (C) 2016 The Japan Society of Applied Physics