Thermoelectric properties of TiS2 mechanically alloyed compounds

Bourges, C., Barbier, T., Guelou, G., Vaqueiro, P. ORCID: https://orcid.org/0000-0001-7545-6262, Powell, A. V., Lebedev, O. I., Barrier, N., Kinemuchi, Y. and Guilmeau, E. (2015) Thermoelectric properties of TiS2 mechanically alloyed compounds. Journal of the European Ceramic Society, 36 (5). pp. 1183-1189. ISSN 1873-619X doi: 10.1016/j.jeurceramsoc.2015.11.025

Abstract/Summary

Bulk polycrystalline samples in the series Ti1−xNbxS2 (0 ≤ x ≤ 0.075) were prepared using mechanical alloying synthesis and spark plasma sintering. X-ray diffraction analysis coupled with high resolution transmission electron microscopy indicates the formation of trigonal TiS2 by high energy ball-milling. The as-synthesized particles consist of pseudo-ordered TiS2 domains of around 20–50 nm, joined by bent atomic planes. This bottom-up approach leads, after spark plasma sintering, to homogeneous solid solutions, with a niobium solubility limit of x = 0.075. Microstructural observations evidence the formation of small crystallites in the bulk compounds with a high density of stacking faults. The large grain boundary concentration coupled with the presence of planar defects, leads to a substantial decrease in the thermal conductivity to 1.8 W/mK at 700 K. This enables the figure of merit to reach ZT = 0.3 at 700 K for x = 0.05, despite the lower electron mobility in mechanically alloyed samples due to small crystallite/grain size and structural defects.