The Study On Thermoelectric Property Of Sige Alloy At High Temperature

This century will be turning on more drastic competition on deep space exploitation, and this reality has been accepted by all the countries at the present time. Every country now is trying her best to develop her firmament exploitation ability for winning the predominance obout deep space and getting atrategic dominance. The experience of deep space exploitation indicate that the Radioisotope Thermoelectric Generator (RTG) is an alternative power source for deep space probes, and in some conditions there are no other choices for the property of safty and reliability. Reliable power supply is the base of deep space exploitation. In China, the study of semiconducror refrigeration has gotten a lot of achievement, and some new kinds of semiconducror refrigerator are for sale. But there are few studies on thermoelectricity because our country is still a less developed country in the field of the military and high technology. There have been several kinds of thermoelectric generators in developed countries made from Te2Bi3 at lower temperature, but SiGe alloy, as one kind of thermal material at high temperature has not been applied proficientily.The thermal parameter, including Seebeck coefficient, electrical conducror and thermal conductivity of the Silicon-germanium alloy samples with different composition, different orientation, different electric conductive type and different carrier concentration will be discussed in this paper. The aim is finding with what basic parameter, the SiGe alloy sample with best thermal properity ,and supplying the fundamental datas and theories found in experiment to SiGe alloy-RTG making.As seen in the experiment, the conversion efficiency is mainly influnced by the migrating of carriers and the scattering of phonon. A larger migrating of carrier can introduce a higher Seebeck voltage because the absolute value of Seebeck coefficient is determined by carrier concentration and atom structure. Decreasing phonon scattering can decrease thermal conductivity. At the same time, thermal conductivity also has relationship with Ge concentration of SiGe alloy.Anisotropy of the thermal property will also be described in this paper. Samples with <100> orientation has higher thermal conversion efficiency that of <111>. The relationship between conductive type and thermal property has a little ambiguous. The average data of ZT of P-type is lardger than that of N-type, but at high temperature, the ZT datas of N-type increase with the increasing of temperature, but the ZT datas of P-type go to the opposite phenomenon.At last, we can get a conclusion according to the result of experiment: the SiGe alloy with best thermal property must exist in the SiGe single crystal of <100> orientation, in which the carries concentration is lardger than 1020cm-3, and with higher Ge concentration.