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

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–XTM_XNiSn (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 Grüneisen 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_0.75Zr_0.25NiSn, Ti_0.75Hf_0.25NiSn, and Ti_0.50Mn_0.50NiSn can reduce κ_lat by 27.19%, 20.26%, and 17.65%, respectively, which shows good potential for enhancing the κ_lat of TiNiSn.