Phonon scattering effects on thermal conductivity of TiNiSn-based half-Heusler alloys

• Published in: Journal of the South Carolina Academy of Science Vol. 6; no. 2; p. 20
• Main Authors: Bhattacharya, S, Tritt, T.M, Skove, M.J, Russell, M, Poon, S.J, Ponnambalam, V, Xia, Y, Thadhani, N
• Format: Journal Article
• Language: English
• Published: South Carolina Academy of Science 22.09.2008
• ISSN: 1553-5975; 1553-5975

TiNiSn-based half-Heusler alloys have been of significant interest for their potential as thermoelectric materials, which arises from their promising electronic transport properties. They exhibit high Seebeck coefficients and moderate electrical resistivity values but have comparatively high lattice thermal conductivities ([κ.sub.L]) that need to be reduced. A significant reduction in [κ.sub.L] with substitutions of large concentrations of Zr (y ≥ 25%) in [Ti.sub.1-y][Zr.sub.y]Ni[Sn.sub.0.95][Sb.sub.0.05] is observed and attributed to mass fluctuation scattering. In contrast, minute amounts of Sb-doping (x ≤ 5%) at the Sn-site in TiNi[Sn.sub.1-x][Sb.sub.x] gives rise to non- systematic increase in [κ.sub.L]. Extensive micro-structural analysis indicate a correlation between [κ.sub.L] and the average grain diameter of these materials. The two different phonon scattering mechanisms to reduce [κ.sub.L] are discussed in the Ti and Zr-based half-Heusler alloys.