UNIVERSITY OF WALES INST OF SCIENCE AND TECHNOLOGY CARDIFF
Lead telluride type semiconductors are used in the fabrication of thermoelectric modules currently employed in a number of US military applications. This report covers a programme to produce materials based upon commercially available lead telluride type material specifically identified as 3P with improved figures of merit and hence greater thermoelectric conversion efficiency. One way of improving the figure of merit is by reducing the lattice thermal conductivity of the material in order to increase phonon-grain boundary scattering. A realistic model has been developed for PbSnTe and used to investigate the dependence of the lattice thermal conductivity on grain size and level doping. Thermal diffusivity measurements on small gain size compacted 3P material indicate that the reduction in lattice thermal conductivity is more than double that predicted by the theoretical model and is comparable to the reduction reported for silicon germanium alloys. The measured electric power factor values do not appear to decrease with a reduction in grain or size.