Microwave synthesis and sintering of TiNiSn thermoelectric bulk

Nano-structured Half-Heusler TiNiSn thermoelectric bulk was prepared by microwave-assisted rapid solid-state synthesis and sintering. The mixture of powders of Ti, Ni, Sn was cold pressed before being heated by microwave irradiation. A microwave susceptor material rapidly heats the elemental starting materials inside an evacuated quartz tube resulting in near single phase compounds in 4 min 20 s. The synthesized sample was milled for 30 min in an agate mortar and cold pressed for the following sintering. An 86% density of TiNiSn thermoelectric bulk contains ∼100 nm pore and nanocrystal was sintered in 20 min. For TiNiSn bulk, low thermal conductivity of 2–3 W/m·K at temperatures in the range of the room temperature to 773 K. The ZT values of around 0.3 are found, with the microwave-prepared sample displaying noticeable superior properties over conventionally prepared half-Heuslers due to inclusion of nanopore and In-situ nanocrystal.