Bo Cui

Enhanced thermoelectric and mechanical properties of p-type skutterudites with in situ formed Fe3Si nanoprecipitate

In the present work, p-type skutterudites La0.8Ti0.1Ga0.1Fe3CoSb12 composite with n-type Fe3Si nanoprecipitate was fabricated via an in situ method. Both thermoelectric and mechanical properties of La0.8Ti0.1Ga0.1Fe3CoSb12/xFe3Si composites were thoroughly investigated. With the introduction of homogeneously dispersed nanosized Fe3Si in the matrix, the power factor is almost unchanged due to the counteraction between the decreased electrical conductivity and the significantly enhanced Seebeck coefficient. Simultaneously, the total thermal conductivity was decreased for samples with Fe3Si nanoprecipitate because of the reduced electronic thermal conductivity. As a result, a ZT value of about 1.2 at 700 K has been achieved for La0.8Ti0.1Ga0.1Fe3CoSb12/0.1Fe3Si sample, whose ZT value was slightly enhanced in comparison with the Fe3Si-freeLa0.8Ti0.1Ga0.1Fe3CoSb12 sample. Furthermore, the indentation fracture toughness of La0.8Ti0.1Ga0.1Fe3CoSb12/0.1Fe3Si was improved by nearly 30% compared to the Fe3Si-free skutterudites.

Thermoelectric SnTe with Band Convergence, Dense Dislocations, and Interstitials through Sn Self-Compensation and Mn Alloying

SnTe is known as an eco-friendly analogue of PbTe without toxic elements. However, the application potentials of pure SnTe are limited because of its high hole carrier concentration derived from intrinsic Sn vacancies, which lead to a high electrical thermal conductivity and low Seebeck coefficient. In this study, Sn self-compensation and Mn alloying could significantly improve the Seebeck coefficients in the whole temperature range through simultaneous carrier concentration optimization and band engineering, thereby leading to a large improvement of the power factors. Combining precipitates and atomic-scale interstitials due to Mn alloying with dense dislocations induced by long time annealing, the lattice thermal conductivity is drastically reduced. As a result, an enhanced figure of merit (ZT) of 1.35 is achieved for the composition of Sn0.94 Mn0.09 Te at 873 K and the ZTave from 300 to 873 K is boosted to 0.78, which is of great significance for practical application. Hitherto, the ZTmax and ZTave of this work are the highest values among all single-element-doped SnTe systems.

The critical role of boron doping in the thermoelectric and mechanical properties of nanostructured α-MgAgSb

The α-MgAgSb compound has attracted intensive attention as a promising candidate for the replacement of the traditional BiSbTe alloy for energy harvesting. Previous investigations have focused on how to enhance the thermoelectric performance while little interest has been placed on the aspect of mechanical properties. Herein, we highlighted the critical role of boron doping on the Sb site in the thermoelectric and mechanical properties of nanostructured α-MgAgSb, which significantly increased the mechanical properties without the deterioration of thermoelectric performance. The ineffectiveness of boron doping to enhance thermoelectric performance lied in the introduced perturbation to the valence band, resulting in a lower carrier mobility and power factor in comparison with that of doping on the Mg site. Due to the significant solution strengthening by boron doping, the corresponding Vickers microhardness values have been largely increased, which can be comparable to those of the mechanically robust p-type filled skutterudite. Our results not only highlight the promising prospect of α-MgAgSb-based materials for power generation but also provide a new and facile way to strengthen thermoelectric materials.

High thermoelectric performance of p-type Cerium single-filled skutterudites by dislocation engineering

Filled skutterudites, possessing a high power factor and good mechanical properties, have attracted intensive attention for the intermediate-temperature power generation. Since n-type filled skutterudites can achieve a high peak ZT of over 1.5, it is imperative to develop their high-performance p-type counterparts for real applications. In this work, single phase p-type cerium (Ce)-filled skutterudites with dense dislocation arrays were first fabricated by the liquid phase compaction method. It was demonstrated that the dense dislocation arrays significantly reduced the lattice thermal conductivity via strain scattering. Simultaneously, there was almost no influence on the normal carrier transport process. As a result, a high peak ZT value of over 1.1 at 723 K has been obtained for the liquid phase compacted Ce0.8Fe3CoSb12 alloy, which is the record-high value among the single element-filled p-type skutterudites.