Composites of Higher Manganese Silicides and Nanostructured Secondary Phases and Their Thermoelectric Properties

Composites of higher manganese silicides (HMS) and hydrothermally synthesized nanostructured Ag₂Te or PbTe powders were fabricated by mechanical mixing and hot-pressing. A reduction of the thermal conductivity and an increase of the Seebeck coefficient were obtained for the Ag₂Te/HMS composite, while the Seebeck coefficient of the PbTe/HMS composite was less influenced and its thermal conductivity decreased too. However, both composites showed a considerably reduced electrical conductivity, which degraded the figure of merit. The lattice contribution was found to be the main part of the thermal conductivity for all the samples. The present results indicate that introducing a secondary phase into a matrix material could be an effective way to reduce the thermal conductivity. On the other hand, a more detailed design of the microstructures and the distribution of the secondary phases is still needed with respect to the effect on the electrical properties.