Electrical and thermal transport properties of Ge substituted SrSi2

• Main Authors: Hong-Yi Liao, 廖紘毅
• Other Authors: Yung- Kang Kuo
• Format: Others
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/44zdgm

碩士 === 國立東華大學 === 物理學系 === 100 === The effects of Ge partial substitution at Si site of the narrow gap semiconductor SrSi2 were investigated by means of thermal and electrical transport measurements. Electrical resistivity (ρ), Seebeck coefficient (S), and thermal conductivity (K) measurements were performed on a series of SrSi2-xGex alloys with x varying from 0 to 0.12 and their thermoelectric performace were evaluated. It is found that room-temperature resistivity of the substituted alloys decreases with substitution up to x = 0.06 and then increases upon further substitution of Ge. The Seebeck coefficient has a substantial increase and a maximum of about 280 μV/K at around 85 K has been found for x=0.03. The observed substitution dependence in the electrical transport properties in these SrSi2-xGex alloys was explained on the basis of broadening of the gap and changes in the density of states (DOS) at the Fermi level. A theoretical analysis of the thermal conductivity of these SrSi2-xGex alloys suggests that the heat transport is essentially associated with the lattice phonons. In addition, the low-T lattice thermal conductivity peak of the SrSi2 alloys was found to be decreased dramatically upon substitution of Ge where the reduction of peak is mainly due to point-defect scattering of the phonons. It is found that the largest figure-of-merit ZT value of ~ 0.13 at room temperature was achieved for the SrSi1.94Ge0.06 alloy, which is almost three times higher than that of pure SrSi2.