Zeming He

Effect of ceramic dispersion on thermoelectric properties of nano-ZrO2∕CoSb3 composites

In the present work, nano-ZrO2∕CoSb3 composites were fabricated by milling ZrO2 and CoSb3 powders and hot pressing at different sintering temperatures. For the prepared compacts, the phase purity, microstructure, and temperature-dependent thermoelectric properties were characterized. The effect of nano-ZrO2 dispersion on composite electrical conductivity and thermal conductivity is strictly clarified by comparing the transport properties of the nondispersed and dispersed CoSb3 at identical porosity, so that the effect of porosity on thermoelectric parameters could be eliminated. The effect of the insulating inclusion itself on transport properties is also considered and eliminated using effective media theories. It is clearly verified that charge carrier scattering and phonon scattering occur simultaneously to lower the electrical conductivity and the thermal conductivity of CoSb3 due to the introduction of nano-ZrO2 inclusions. The investigated composites show higher electrical conductivity due to existe...

Nano ZrO2/CoSb3 composites with improved thermoelectric figure of merit

Nano ZrO2/CoSb3 composites with different ZrO2 contents were prepared using hot pressing. The phase purity, the microstructure and the temperature-dependent transport parameters of the composites were investigated. The dimensionless figure of merit (ZT) of 0.18 of the non-dispersed CoSb3 preponderates the maximal value (0.17) of pure CoSb3 reported in the literature, which is attributed to the prepared sample having higher electrical conductivity due to the existence of a small amount of metallic Sb and lower thermal conductivity due to the fine-grained structure. Compared to non-dispersed CoSb3, a further improvement of 11% on ZT (0.20) was achieved in the composite with 0.05ZrO2 inclusions, which resulted from the enhanced ratio of electrical conductivity to thermal conductivity and the Seebeck coefficient. The nanodispersion method provides an effective approach to improving a material’s thermoelectric properties and performance.

Thermoelectric properties of hot-pressed skutterudite CoSb3

In the present work, skutterudite CoSb3 were fabricated by hot pressing at different sintering temperatures under vacuum and argon. For the prepared compacts, the phase, the microstructure, and the ...

Processing and Characterization of Nano-structured ZrO2/CoSb3 Thermoelectric Composites

The addition of ceramic inclusion to a thermoelectric matrix could reduce the thermal conductivity of the composite, which is attributed to phonon scattering on the generated interfaces. The electrical conductivity of the composite, however, could also be reduced due to additional charge carrier scattering. The performance of the thermoelectric composite, therefore, depends on the resulting ratio of electrical conductivity to thermal conductivity, which results from the entire scattering effects on phonons and charge carriers. In the present work, nano-sized ZrO2 powders of different contents, which were expected to minimize their scattering impact on charge carriers, were dispersed into sub-micron-sized CoSb3 powders via ball milling. The as-milled powders were consolidated into dense compacts by hot pressing. The phase, the microstructure, and the thermoelectric properties of the prepared compacts were characterized. The correlation of phase purity, microstructure, and thermoelectric properties (electrical conductivity, thermal conductivity, and ratio of electrical conductivity to thermal conductivity), with the ceramic content and sintering temperature is presented. The results show how the performance of the investigated thermoelectric composites can be affected by the dispersion of nano-sized ceramic inclusions. It is noted that the selection of appropriate inclusion content is crucial to maintaining or improving the ratio of electrical conductivity to thermal conductivity

Influence of Phase Composition on the Thermoelectric Properties of Nanostructured Skutterudite and Ceramic Composites

Nanostructuring of unfilled CoSb3 Skutterudites has been successful in reducing the thermal conductivity of these materials [Toprak, et al., 2004]. First measurements on a mixture of the Skutterudite and an inert ceramic with particle sizes in the nanometer range have shown promising results for a further reduced thermal conductivity by decorating the grain boundaries of the thermoelectric material [Stiewe, et al., 2006]. A strong influence of additional phases like CoSb2 and pure Sb in the samples has been encountered, too. Therefore in the present work a more detailed investigation of the effect of phase purity and grain size by an intentional variation of the phase composition is presented. The impact of a variation in the amount of the ceramics addition and of the phase composition on the thermoelectric properties (kappa, sigma, S) of pure and doped CoSb 3, respectively, are studied and the results are discussed with respect to an enhancement of the thermoelectric figure of merit