Decoupling the Electrical Conductivity and Seebeck Coefficient in the <i>RE</i>₂SbO₂ Compounds through Local Structural Perturbations

Abstract

Compromise between the electrical conductivity and Seebeck coefficient limits the efficiency of chemical doping in the thermoelectric research. An alternative strategy, involving the control of a local crystal structure, is demonstrated to improve the thermoelectric performance in the <i>RE</i>₂SbO₂ system. The <i>RE</i>₂SbO₂ phases, adopting a disordered <i>anti</i>-ThCr₂Si₂-type structure (<i>I</i>4/<i>mmm</i>), were prepared for <i>RE</i> = La, Nd, Sm, Gd, Ho, and Er. By traversing the rare earth series, the lattice parameters of the <i>RE</i>₂SbO₂ phases are gradually reduced, thus increasing chemical pressure on the Sb environment. As the Sb displacements are perturbed, different charge carrier activation mechanisms dominate the transport properties of these compounds. As a result, the electrical conductivity and Seebeck coefficient are improved simultaneously, while the number of charge carriers in the series remains constant