"There is an increasing demand for alternative energy technologies to reduce our reliance on fossil fuels. One approach is to use thermoelectric (TE) materials to scaving waste heat energy and to convert it into useful electrical energy. Thermoelectric materials have the additional potential advantages that they could be: small, inexpensive, lightweight, quiet and pollution-free. These applications call for thermoelectric materials with high zT which requires higher Seebeck coefficient, higher electrical conductivity, and lower thermal conductivity. In this project, two strategies are used to reduce lattice thermal conductivity and then improve the zT: one is phonon-glass substitution within the unit cell by creating point defects such as interstitials and vacancies; another is the introduction of more interfaces on the nanometre scale. Using these approaches, we will identify promising optimised compositions, control the grain morphology and size, and sinter plate-like powders by Spark Plasma Sintering (SPS), to produce (Ag, Se, Ba, Yb, et al) doped Bi2Te3 and CoSb3-based bulk layer-textured nanomaterials. Through the optimization of the compostion, sintering process and microstructure it may be possible to significantly enhance zT. The main objective of this work is to develop thermoelectric nanomaterials and devices with zT values >2 to replace current commerical materials. Meanwhile, The research will also improve the fundamental understanding of these materials. At the microscale, stress and size effects on the thermal conductivity and zT properties will be studied and the mechanisms involved will be established."