Influence of the addition of HfO2 particles on the thermoelectric properties of an N-type half-Heusler alloy sintered by spark plasma sintering

An N-type Ti0.5Zr0.5NiSn0.994Sb0.006 powder, synthesized by levitation melting, has been mixed with 1.5 wt% of HfO2 particles and sintered by spark plasma sintering (grain size around 10 μm). Three kinds of nanocrystalline particles have been identified in the sintered microstructure. They are thought to promote scattering of lattice vibrations, leading to a 25% increase of the dimensionless-thermoelectric figure of merit (ZT, around 1.0 at 500 °C) in comparison to the standard Zr0.25Hf0.25Ti0.5NiSn0.994Sb0.006 composition. In the same time, the replacement of Hf by HfO2 leads to a significant decrease (in the range 25–60%) of the cost per kilogram of raw material. [Display omitted] •An N-type half-Heuler composition incorporating 1.5wt% of HfO2 particles has been sintered using SPS.•The sintered microstructure exhibits three kinds of submicrometer/nanometer-sized particles.•A 25% increase of the ZT value at 500 °C with 25–0% reduction of the cost per kilogram of material is obtained.