Large thermal conductivity reduction induced by La/O vacancies in the thermoelectric LaCoO₃ system

A series of compact La/O-vacant La_1-xCoO_3-y compounds were prepared by a cold high-pressure procedure, and their thermoelectric (TE) properties were investigated. Compared with the ion-substituted hole-type LaCoO₃ systems (e.g., La_1-xSr_xCoO₃), the thermal conduction of La_1-xCoO_3-y is noticeably reduced by the La/O vacancies, whereas the electric transport is less influenced, which results in an efficient ZT enhancement. We demonstrate that the large thermal conductivity reduction originates from the strong point-defect scattering, and La_1-xCoO_3-y can be rationalized as a partially filled solid solution: La_1-x□_xCoO _3-y□_y, where □ denotes a vacancy. Such intrinsic thermal conductivity suppression provides an effective pathway for the design of better TE materials.