Thermoelectric properties, crystal and electronic structure of semiconducting RECuSe2 (REÂ =Â Pr, Sm, Gd, Dy and Er)

The ternary RECuSe2 phases have been prepared and structurally characterized. They adopt either a monoclinic structure (P21/c, z = 4) for lighter rare earths (RE = Pr, Sm and Gd) or Cu-disordered trigonal structure for heavier rare-earths (P3¯m1, z = 1, RE = Dy and Er). The resistivity and Seebeck coefficient measurements on GdCuSe2, DyCuSe2 and ErCuSe2 indicate that the studied phases are p-type semiconductors with relatively small activation energies (0.045-0.11 eV). However, their electrical resistivities are too high (0.45-220 Ω cm at room temperature) to make them competitive thermoelectric materials. Electronic structure calculations indicate presence of a band gap in the RECuSe2 phases.