Microstructure investigations and thermoelectric properties of an N-type Half-Heusler alloy sintered by spark plasma sintering

An N-type Zr0.25Hf0.25Ti0.5NiSn0.994Sb0.006 powder, directly prepared by levitation melting from the raw elements, has been sintered by spark plasma sintering at different temperatures. SEM and TEM observations enabled to detect two sorts of nano-sized precipitates mostly dispersed in the bulk of individual grains constituting the sintered polycrystal (grain size around 3–4μm, depending on the sintering temperature). These precipitates are thought to scatter lattice vibrations, leading to a dimensionless-thermoelectrical figure of merit (ZT) around 0.91 at 500°C for the sample sintered at 1140°C. [Display omitted]