Remarkable Enhancement in Thermoelectric Performance of BiCuSeO by Cu Deficiencies

A significant enhancement of thermoelectric performance in layered oxyselenides BiCuSeO was achieved. The electrical conductivity and Seebeck coefficient of BiCu1-xSeO (x = 0-0.1) indicate that the carriers were introduced in the (Cu2Se2)(2-) layer by Cu deficiencies. The maximum of electrical conductivity is 3 x 10(3) S m(-1) for Bicu(0.975)Seo at 650 degrees C, much larger than 470 S m(-1) for pristine BiCuSeO. Featured with very low thermal conductivity (similar to 0.5 W m(-1) K-1) and a large Seebeck coefficient (+273 mu V K-1), ZT at 650 degrees C is significantly increased from 0.50 for pristine BiCuSeO to 0.81 for BiCu0.975SeO by introducing Cu deficiencies, which makes it a promising candidate for medium temperature thermoelectric applications.