| Summary: | 碩士 === 輔仁大學 === 物理學系 === 91 === The high-temperature α-phase of FeSi2 is metallic while low-temperature β-phase is a semiconductor . In this thesis we present the study of thermopower S, thermal conductivityκand electrical conductivityσ of α and β-phases of FeSi2 . Furthermore, the values of Figure of Merit Z = S2σ/κwere calculated and the results shows β- FeSi2 had higher thermpower as well as higher efficiency Z compared with theα- FeSi2.
The nanoparticles of β- FeSi2 were fabricated by different methods such as flash evaporation, EDM and ball milling. We discuss how the size effects on S,κandσ inβ- FeSi2. The result show that the values of S, κ and σ in β- FeSi2 nanoparticles were smaller than the bulk. The specific heat of β- FeSi2 nanoparticles was higher than the bulk at 0.3 to 30 K . The magnetic susceptibility of β- FeSi2 nanoparticles and bulks were measured from 2 to 300 K, and the results reveals thatβ- FeSi2 nanoparticles have superparamagnetism and Blocking Temperature at 70
K.
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