Grain oriented ceramics of layer-structured n-type oxide for high thermoelectric performance

Homologous compounds of (ZnO)_mIn₂O₃ (m: integer) with layered structures show comparatively high thermoelectric properties as oxide materials, and we have reported that the in-plane (hexagonal ab plane) conductivity is 10 times as large as the cross-plane conductivity (hexagonal c-axis). To apply such crystals with structural anisotropy to thermoelectric materials, we need a thermal gradient in the direction of highest conversion efficiency. We fabricated textured (ZnO)₅In₂O₃ polycrystals by the RTGG method which includes in-situ reaction of template ZnO particles with plate-like shape and fine In₂O ₃ particles, and thermoelectric properties were evaluated. Three times as high figure of merit Z(=σ α²/κ) as that of the non-textured specimen was achieved by texturing. This time we report the accomplishment of higher thermoelectric properties by textured polycrystals of (ZnO)₅In_0.97Y_0.03O₃