An energy transformation is the change of energy from one form to another. Energy transformations occur everywhere every second of the day. There are many different forms of energy such as electrical, thermal, nuclear, mechanical, electromagnetic, sound, and chemical.
High performance thermoelectric (TE) materials that can directly and reversibly convert heat to electrical energy have thus draw growing attentions of governments and research institutes . Thermoelectric system is an environment-friendly energy conversion technology with the advantages of small size, high reliability, no pollutants and feasibility in a wide temperature range.