Novel n‐type Zintl phase thermoelectric materials: The Ca5−xRExAl2Sb6 (RE = Pr, Sm) system

Abstract Two novel n ‐type Zintl thermoelectric materials of Ca 4.97(1) Pr 0.03 Al 2 Sb 6 and Ca 4.94(2) Sm 0.06 Al 2 Sb 6 were synthesized with the addition of two types of trivalent rare‐earth metals dopants and characterized by powder and single crystal x‐ray diffraction analyses. Two title compounds adopted the orthorhombic Ca 5 Ga 2 As 6 ‐type phase and contained seven crystallographically unique atomic positions including one particular Ca/Pr or Ca/Sm mixed‐site. The crystal structure can be described as a combination of the one‐dimensional (1D) infinite chains and the cationic elements in between the 1D chains. Electrical transport property measurements proved that Ca 4.97(1) Pr 0.03 Al 2 Sb 6 and Ca 4.94(2) Sm 0.06 Al 2 Sb 6 were indeed novel n ‐type Zintl phase semiconductors with the maximum electrical conductivities of 69.51 and 75.51 S/cm at 846 K and the Seebeck coefficients of −43.26 and − 29.00 μV/K at 703 K, respectively. Density functional theory calculations proved that the successful n ‐type doping should be attributed to a small margin of slight antibonding states near E F on the Sb1Sb1 crystal orbital Hamilton population (COHP) curve.