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Abstract:
Zintl phase compounds AM(2)Sb(2) (A= Ca, Sr, Ba, Eu, Yb; M= Zn, Cd) is a new class of promising thermoelectrics owing to their intrinsic features in electronic and crystal structure, such as a small or even disappeared band-gap, large density-of-states at the Fermi level, covalently bonded network of M-Sb, as well as the layered stacking by cations A(2+) and anionic slabs (M2Sb2)(2-). In addition, the rich solid-state chemistry of Zintl phase allows structural modification and chemical substitution to adjust the fundamental transport parameters (carrier concentration, mobility, effective mass, electronic and lattice thermal conductivity) for improving the thermoelectric performance. In the present review, the recent advances in synthesis and thermoelectric characterization of title compounds AM(2)Sb(2) were presented, and the effects of alloying or substitution for sites A, M and Sb on the electrical and thermal transport were emphasized. The structural disorder yielded by the incorporation of multiple ions significantly increased the thermoelectric figure of merit mainly resulted from the reduction of thermal conductivity without disrupting the carrier transport region in substance. Therefore, alloying or substitution has been a feasible and common route utilized to enhance thermoelectric properties in these Zintl phase compounds, especially for YbZn0.4Cd1.6Sb2 (ZT(700) (K)=1.26), EuZn1.8Cd0.2Sb2 (ZT(650 K)=1.06), and YbCd1.85Mn0.15Sb2 (ZT(650 K)=1.14).
