Abstract
Having recently succeeded in synthesizing large single crystals of (Ca2CoO3)CoO2(Co-349) with superior thermoelectric properties and in high yields of about 30% using a modified flux method, we have prepared a composite material of Co-349 powder and single crystals and examined its thermoelectric properties. The electrical resistivity p of this composite containing 20 wt.% single crystals is found to be lower than that of the sample without the single crystals. Improved grain alignment and the effect of current bypassing grain boundaries through the large single crystals in the composite are thought to cause the suppressed ρ, which consequently results in an enhanced thermoelectric figure of merit about 0.56 at 973 K in air.
