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

Homologous compounds of (ZnO)/sub m/In/sub 2/O/sub 3/(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)/sub 5/In/sub 2/O/sub 3/ polycrystals by the RTGG method which includes in-situ reaction of template ZnO particles with plate-like shape and fine In/sub 2/O/sub 3/ particles, and thermoelectric properties were evaluated. Three times as high figure of merit Z(=/spl sigma/ /spl alpha//sup 2///spl kappa/) 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)/sub 5/In/sub 0.97/Y/sub 0.03/O/sub 3/.