Reduced lattice thermal conductivity of Ti-site substituted transition metals Ti1-XTMXNiSn: A quasi-harmonic Debye model study

Abstract TiNiSn thermoelectric (TE) material has a high power factor, but it also has high thermal conductivity, which is a problem for low performance. In this work, we propose to reduce the lattice thermal conductivity ( κ lat ) of the transition metal (TM) with substitution on the Ti-site TiNiSn as the model Ti 1–X TM X NiSn (TM = Sc, Zr, Hf, V, Nb and Mn) by the quasi-harmonic Debye model calculation from 0 – 1000 K. The structural properties were investigated through the equation of state by a first-principles calculation. κ lat was calculated by the Slack and Berman method using the Debye temperature (Θ) and Gruneisen parameter. The calculated results revealed that the structure increased with substitution by Sc, Zr, Hf, and Nb, but V and Mn exhibit a structure less than that of TiNiSn. The calculated Θ of TiNiSn is 404.86 K decreased with substitution by Sc, Zr, Hf, Nb, and Mn, and then slightly increased by V. The Sc, Zr, Hf, and Mn substitution significantly decreases the calculated κ lat from 9.23 W m –1  K –1 (for TiNiSn) to 6.72 – 9.07 W m –1  K –1 at 300 K. Ti 0.75 Zr 0.25 NiSn, Ti 0.75 Hf 0.25 NiSn, and Ti 0.50 Mn 0.50 NiSn can reduce κ lat by 27.19%, 20.26%, and 17.65%, respectively, which shows good potential for enhancing the κ lat of TiNiSn.