Abstract
The (Zn0.98Al0.02)O ceramic is known to show high dimensionless figure of merit(ZT)at high temperature among the n-type oxide materials. But it has problem of the large lattice thermal conductivity compared with other thermoelectric materials. However the lattice thermal conductivity can be decreased by grain refining, and further improvement in the ZT value is possible. Thus we have tried to synthesize homogeneous (Zn0.98Al0.02)O powders with fine particles size by mechanical alloying(MA), and make the fine grained and dense (Zn0.98Al0.02)O ceramic under several sintering conditions, expeceting the increase of ZT value due to the decrease in lattice thermal conductivity. We found an optimum MA condition for grain refinement, but homogeneous (Zn0.98Al0.02)O powders could not be obtained under present MA conditions. The fine grained and dense (Zn0.98Al0.02)O ceramic obtained by MA/HP process shows the decrease in lattice thermal conductivity. Hot pressing was found to decrease the absolute value of Seebeck coefficient and increase the electrical conductivity as compared with the normal sintering (NS). MA/HP process will increase the amount of the substituted Al for Zn. The ZT value became the maximum by the MA/NS; ZT=0.13 at 1073K.
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