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p -type filled skutterudite / GaSb nano- composites and thermoelectric properties of

Author: GuoQuanSheng
Tutor: TangXinFeng
School: Wuhan University of Technology
Course: Materials Science
Keywords: Gasb Melt spinning method p -type compound filled square diamond mines Nanocomposites Thermoelectric properties
CLC: TB383.1
Type: Master's thesis
Year: 2011
Downloads: 80
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Abstract

Filled Skutterudite (skutterudite) compounds due to show \In this paper, the p-type skutterudites as the main object of study, the first use of \thermoelectric material through the grain boundary or in the nano-crystalline phase may result in GaSb carrier energy filter effect and the electrical interface effect of the material, respectively - to optimize heat transfer characteristics. On this basis, the use of \the existence of elements in the form of Ga and distribution of the content is analyzed different GaSb microstructure of the material characteristics, revealing the GaSb content on the material microstructure and thermoelectric properties were investigated. The main results are as follows: (1) on the use of \in the sample. FESEM and EDX results showed that the main components of the sample particle size distribution in the range of 5-30μm CeFe4Sb12 square diamond mines, the matrix grain boundary uniformly distributed nano-GaSb second phase, and with the increase in the content of the sample GaSb, GaSb, the average grain particle size from 100 nm gradually increased to 500 nm. Thermal performance test results show, CeFe4Sb12/0.2GaSb sample because of its high electrical conductivity and Seebeck coefficient, and due to the special nanostructures can strong phonon scattering to have the lowest thermal conductivity of the lattice, so CeFe4Sb12/0.2GaSb with best overall thermoelectric performance, the ZT value reaches a maximum 0.96 at 800K, compared with single-phase CeFe4Sbi2 increased by nearly 30%. (2) using the MS-SPS preparation of p-type CeFe4-xCoxSb12 (0 ≤ x ≤ 1) lattice constant increases with the Co content decreases linearly, and with the Co content increases, CeFe4-xCoxSb12 compounds and thermal conductivity decreased conductivity, Seebeck coefficient and the Seebeck coefficient increases peak temperature shift to lower temperature. A moderate electrical conductivity and Seebeck coefficient and low thermal conductivity of the sample CeFe3.5Co0.5Sb12 exhibit high ZT value, between 725K-800K of the sample with the largest thermoelectric dimensionless performance index 0.85 . (3) MS-SPS prepared using p-type CeyFe3.5Co0.5Sb12 (0.6 ≤ y ≤ 1) of the high-angle XRD peaks with the decrease of the Ce content to the high-angle shift. CeyFe3.5Ca0.5Sb12 compounds exhibit metallic conductivity characteristics, conductivity increases with the decrease of Ce filling fraction increases. CeyFe3.5Co0.5Sb12 Seebeck coefficient is positive, and the variation of the conductivity opposite. The results show that the lattice thermal conductivity of Ce and empty location quality fluctuation caused significantly greater than the difference in quality between Fe and Co, thus partially filling a greater extent can reduce the lattice thermal conductivity; Ceo.9Fe3.5Coo.5Sb12 time at 750K has the largest figure of merit 0.87. (4) MS-SPS prepared using p-type Ceo.9Fe3.5Coo.5Sbl2 z (0 ≤ z ≤ 0.6) of the electrical conductivity decreases with increasing temperature, the performance of metallic conductivity. Although excess Sb conductivity of the material can be improved, but the introduction of mixed conducting mechanism reducing the Seebeck coefficient. The thermal conductivity increases with increasing the content of Sb, Sb, introducing a large thermal conductivity of the sample was significantly increased, significant thermal degradation of performance, particularly in the high temperature region. (5) prepared by using the MS-SPS CeFe3.5Co0.5Sb12/mGaSb (m = 0.2,0.4,0.6) prepared by the conventional method CeFe4Sb12/xGaSb samples significantly different microstructures. FESEM and TEM analysis showed CeFe3.5Co0.5Sb12 skutterudite substantially matrix grain size refinement, down 100 nm-300 nm, the internal matrix grain size distribution of 10 ~ 20 nm GaSb nanodots. Thermoelectric Performance tests show: amount of doped GaSb material in maintaining good electrical transmission performance while significantly reducing thermal conductivity, m = 0.2 sample has the best overall thermoelectric performance, the dimensionless ZT value reaches a maximum at 725K 0.96 in the same temperature region above the other components of the sample values of ZT.

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