High Defect Tolerance in Heavy‐Band Thermoelectrics.

The insensitivity of thermoelectric (TE) performance to defects and impurities induced by off‐stoichiometry or low‐purity raw elements is crucial for the low‐cost mass production of highly efficient TE materials. Here it is demonstrated that heavy‐band TE materials with high optimized carrier concentration can exhibit a high tolerance against the off‐stoichiometry in their composition. Using the heavy‐band half‐Heusler compounds as examples, it is found that for ZrNiSn with optimal carrier concentration, the off‐stoichiometry of the nominal composition in between ±5% only results in a fluctuation of its peak zT value less than 10%. A composition‐zT phase diagram is thus established, guiding the exploration of a wide nominal composition region with peak zT values exceeding 1.0. The high defect tolerance observed in heavy‐band TE materials enables the achievement of high TE performance using low‐purity raw elements. As demonstrated in several systems, including n‐type ZrNi(Sn, Sb), (Zr, Nb)CoSb, and p‐type ZrCo(Sb, Sn), comparable zT values are attained when utilizing low‐purity raw elements (≈99.5%), instead of the high‐purity ones (99.95–99.999%), leading to substantial cost saving. These findings highlight the importance of understanding defect tolerance in TE materials, which could offer an additional advantage for their practical applications. [ABSTRACT FROM AUTHOR]