Thermoelectric Properties of Nanocrystalline PbTe Synthesized by Mechanical Alloying

In this work, nanocrystalline lead telluride powder was synthesized from high-purity elements by mechanical alloying by means of a planetary ball-milling procedure. The milling medium was tungsten carbide, and the diameter of the balls was varied in order to investigate the effect on the structural features of the material. Phase transformations and crystallite evolution during ball-milling were followed by powder x-ray diffraction (PXRD). The broadened PXRD peaks were analyzed with Voigt functions, revealing small crystalline size and stress introduced during the mechanical alloying process. Transmission electron microscopy (TEM) studies confirmed the material's nanostructure, as well as the effect of ball diameter on the size of the crystals. Thermoelectric properties are discussed in terms of the Seebeck coefficient and the nominal carrier concentration, as determined by Hall-effect measurements. The enhancement of the Seebeck coefficient is reported to be higher compared with other PbTe-based nanocomposites.