Effect of temperature variation on the transport properties of fine-grained heavily doped n-type PbTe

The electrical conductivity, Seebeck coefficient, thermal conductivity, and figure-of-merit, which is a measure of the performance of the thermoelectric material, of heavily doped n-type PbTe single crystal and compacts of grain size in the range 10 less than or equal to L less than or equal to 20 mum and very fine powder L similar to 1 mum, are measured in the temperature range 300-750 K. Effect of the grain size on decreasing the lattice thermal conductivity lambda (L) and the total thermal conductivity lambda (t), is demonstrated. A drop of 35% in lambda (L) has been achieved at 750 K for the very fine powder. Also, the figure-of-merit Z of the very small grain size, L similar to 1 mum, n-type PbTe compacts improve by 9.41% at 750 K while the large grain size material, 10 less than or equal to L less than or equal to 20 mum, achieve 7.35% increase in Z, at the same temperature, as compared with the single-crystal material. The result confirms that the very fine powder material is superior to large grain size or single-crystal material for thermoelectric power generation. This result is very important in the thermoelectric industry and related devices. (C) 2001 Elsevier Science B.V. All rights reserved.