Rattling-like scattering behavior in ALiSb (A = Ca, Sr, Eu, Yb) Zintl phases with low thermal conductivity

In this report, for the first time TiNiSi-type Zintl phases with the nominal formulae of ALiSb (A = Ca, Sr, Eu, Yb) were systematically investigated on their thermoelectric properties. The results indicated that ALiSb Zintl phases possessed intrinsically low lattice thermal conductivity despite the simple structure. In combination of thorough crystallographic and theoretical investigation, rattling-like scattering behavior originating from the Li atoms was suggested. As a result, the pristine ALiSb materials featured decent zT values of 0.4–0.7 at 823 K. With the electrical and thermal transport properties further optimized by configuring the solid solutions such as Sr0.8Eu0.2LiSb, the material approached a maximum zT up to 1.2 at the same temperature. These breakthroughs are distinct from the previous knowledge that low thermal conductivity in Zintl phases is usually realized through complex crystal structures, and for compounds with simple structures such as the TiNiSi type it is common to have poor thermoelectric performance. Owing to such a rattling-like scattering behavior, now light-element containing Zintl phases can be a promising resource for thermoelectric considerations as well. The mechanism is surely interesting and worth of in-depth investigation.