Composition\nGoverned Structure Evolution and Thermoelectric\nProperties in Eu(Li<sub>1–2<i>x</i></sub>Zn<sub><i>x</i></sub>)Sb (0< <i>x</i> < 0.5) Zintl Phases

In this report, a new series of Zintl phases, Eu(Li<sub>1–2<i>x</i></sub>Zn<sub><i>x</i></sub>)Sb (0 < <i>x</i> < 0.5), was discovered and investigated.\nThese phases\nexhibit rich structural chemistry and notable thermoelectric properties.\nFor the structures of Eu(Li<sub>1–2<i>x</i></sub>Zn<sub><i>x</i></sub>)Sb, three classes of analogues have\nbeen identified, which can be best represented by the well-known TiNiSi,\nLiGaGe, and ZrBeSi types, respectively. Interestingly, the structures\nof Eu(Li<sub>1–2<i>x</i></sub>Zn<sub><i>x</i></sub>)Sb phases are strongly dependent on the compositions varied\nwith Li/Zn ratios. As a result, Eu(Li<sub>1–2<i>x</i></sub>Zn<sub><i>x</i></sub>)Sb features a highly complex\npolyanionic framework as well as inherently low thermal conductivity.\nIn addition to the converged band structures and improved effective\nmass, Eu(Li<sub>1–2<i>x</i></sub>Zn<sub><i>x</i></sub>)Sb materials exhibit excellent thermoelectric performance.\nDemonstrated by Eu(Li<sub>0.5</sub>Zn<sub>0.25</sub>)Sb, exceptionally\nlow thermal conductivity has been confirmed generally below 0.5 W/(m\nK), which led to a remarkable figure of merit (ZT) of 1.12 at 823\nK. This value is about 14 times the maximum experimental ZT reported\nfor the isotypic LiZnSb material. These results could bring new understandings\non the structure-and-property correlations within the Zintl-phase-based\nthermoelectric materials since previously the performance of the p-type\nLiZnSb material was rather difficult to optimize. Besides, Eu(Li<sub>1–2<i>x</i></sub>Zn<sub><i>x</i></sub>)Sb phases established a very significant connection among the well-known\nTiNiSi, LiGaGe, and ZrBeSi structures, which classify three important\nthermoelectric Zintl systems represented by EuLiSb, LiZnSb, and EuZn<sub>0.5</sub>Sb.