n-type thermoelectric material Mg2Sn0.75Ge0.25 for high power generation

Thermoelectric power generation is one of the most promising techniques to use the huge amount of waste heat and solar energy. Traditionally, high thermoelectric figure-of-merit, ZT, has been the only parameter pursued for high conversion efficiency. Here, we emphasize that a high power factor (PF) is equivalently important for high power generation, in addition to high efficiency. A new n-type Mg2Sn-based material, Mg2Sn0.75Ge0.25, is a good example to meet the dual requirements in efficiency and output power. It was found that Mg2Sn0.75Ge0.25 has an average ZT of 0.9 and PF of 52 mu W center dot cm(-1)center dot K-2 over the temperature range of 25-450 degrees C, a peak ZT of 1.4 at 450 degrees C, and peak PF of 55 mu W center dot cm(-1)center dot K-2 at 350 degrees C. By using the energy balance of one-dimensional heat flow equation, leg efficiency and output power were calculated with T-h = 400 degrees C and T-c = 50 degrees C to be of 10.5% and 6.6 W center dot cm(-2) under a temperature gradient of 150 degrees C center dot mm(-1), respectively.