Thermal Expansion and Thermoelectric Properties of n‐Type and p‐Type Half‐Heusler TiNiSn‐Based Alloys

The use of TiNiSn‐based materials, relatively low‐cost and low‐toxicity, facilitates the development of practical thermoelectric conversion modules. Understanding their thermal expansion is important for module integration. The present study investigated the thermomechanical compatibility of these materials. Using dilatometry, the thermal expansion coefficient ( ) values of n‐type TiNiSn and the p‐type half‐Heusler alloy TiNi _0.92 Co _0.05 Sn are investigated up to 900 K. The difference in between the two compounds (10.0 × 10 ^{− 6} K ^{− 1} for TiNiSn and 9.3 × 10 ⁻⁶ K ⁻¹ for TiNi _0.92 Co _0.05 Sn) from 550 to 900 K is within 7%. This close match, attributed to their identical crystal structures and similar compositions, indicates that TiNi _0.92 Co _0.05 Sn possesses superior compatibility for module fabrication compared to the conventional p‐type TiCoSb. Beyond these thermomechanical properties, the practical fabrication of TiNiSn‐based modules will require further optimization of peripheral materials, including electrodes and substrates.