Thermoelectric properties of TiS2 mechanically alloyed compounds

• Published in: Journal of the European Ceramic Society Vol. 36; no. 5; pp. 1183 - 1189
• Main Authors: Bourgès, Cédric, Barbier, Tristan, Guélou, Gabin, Vaqueiro, Paz, Powell, Anthony V., Lebedev, Oleg I., Barrier, Nicolas, Kinemuchi, Yoshiaki, Guilmeau, Emmanuel
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-04-2016; Elsevier
• Subjects: Chemical Sciences; Cristallography; Material chemistry; Mechanical alloying; or physical chemistry; Theoretical and; Thermoelectric; Titanium disulfide; Titanium disulfide; Mechanical alloying; Thermoelectric
• ISSN: 0955-2219; 1873-619X
• DOI: 10.1016/j.jeurceramsoc.2015.11.025

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 20–50nm, 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 1.8W/mK at 700K. This enables the figure of merit to reach ZT=0.3 at 700K for x=0.05, despite the lower electron mobility in mechanically alloyed samples due to small crystallite/grain size and structural defects.