Doping Effects on Thermoelectric Properties of Semiconductor Cu3(Sb1-xMx)Se4 , M= Ti, Sn, Pb, and Ge
| Autor: | Chang, Chia Hsiang, 張家祥 |
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| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 103 Cu3SbSe4 is a p-type semiconductor with a narrow band gap near 0.3 eV, and has been found to be a promising thermoelectric material at medium temperatures. The crystal structure of Cu3SbSe4 consists a three-dimensional [Cu3Se4] framework acting as electron hole conduction pathway which cause high power factor near 900 μW/mK2. The inserting guest atom to the Sb site of tetrahedral [SbSe4] framework cause a more distorted diamond-like structure, thus providing a relatively lower lattice thermal conductivity in relatively large electric conductivity. According to theoretical predication which are based on the defect formation energy and band structure calculations, p-type doping can be achieved by substituting Sb with group IV elements, as Ge, Sn, and Pb, and transition metals as Ti. This study is investigation of the doping effect in Cu3SbSe4 semiconductor which are prepared by melting and spark plasma sintering. Herein, we take a close look at the thermoelectric properties of Cu3SbSe4 which are mentioned in previous paragraph. No significant change in results of Ti and Pb. Carrier concentrations are dramatic increasing in results of Sn and Ge, but the results of Sn substitution were already reported by another group. Power factor of Ge substitution is 1,200μW/mK2 which is 30 % more than raw material. We did more study in germanium doping series because it have high power factor which did not be investigated in Cu3SbSe4. Alloy effects, as description of lattice thermal conductivity reducing with doping fraction increasing, are explored in Ge doping fraction from 1 % to 8 %. Although electric conductivity were largely enhanced, figure of merit were reducing by electric contribution of thermal conductivity were higher than 50 % and carrier mobility were significantly reducing when the doping fraction were higher than 4 %. Doping fraction in 4 % have relatively high power factor and relatively low thermal conductivity. Figure of merit in 4 % doping fraction is 0.7, as 30% more than 0.5 of raw material. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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