Achieving high electronic mobility and excellent thermoelectric performance in GeTe through Ge vacancy suppression and band structure engineering.

Two-step sintering efficiently enhances zT by tuning the microstructure in a wide range from atomic defects to micrometer second phase.

Microstructure engineering is an effective strategy to reduce lattice thermal conductivity (κ ) and enhance the thermoelectric figure of merit (zT). Through a new process based on melt-centrifugation to squeeze out excess eutectic liquid, microstructure modulation is realized to manipulate the formation of dislocations and clean grain boundaries, resulting in a porous network with a platelet structure. In this way, phonon transport is strongly disrupted by a combination of porosity, pore surfaces/junctions, grain boundaries, and lattice dislocations. These collectively result in a ≈60% reduction of κ compared to zone melted ingot, while the charge carriers remain relatively mobile across the liquid-fused grains. This porous material displays a zT value of 1.2, which is higher than fully dense conventional zone melted ingots and hot pressed (Bi,Sb) Te alloys. A segmented leg of melt-centrifuged Bi Sb Te and Bi Sb Te could produce a high device ZT exceeding 1.0 over the whole temperature range of 323-523 K and an efficiency up to 9%. The present work demonstrates a method for synthesizing high-efficiency porous thermoelectric materials through an unconventional melt-centrifugation technique.

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P–type SnS compound and SnS1−xSex solid solutions were prepared by mechanical alloying followed by spark plasma sintering (SPS) and their thermoelectric properties were then studied in different compositions (x = 0.0, 0.2, 0.5, 0.8) along the directions parallel (//) and perpendicular (⊥) to the SPS–pressurizing direction in the temperature range 323–823 Κ. SnS compound and SnS1−xSex solid solutions exhibited anisotropic thermoelectric performance and showed higher power factor and thermal conductivity along the direction ⊥ than the // one. The thermal conductivity decreased with increasing contents of Se and fell to 0.36 W m−1 K−1 at 823 K for the composition SnS0.5Se0.5. With increasing selenium content (x) the formation of solid solutions substantially improved the electrical conductivity due to the increased carrier concentration. Hence, the optimized power factor and reduced thermal conductivity resulted in a maximum ZT value of 0.64 at 823 K for SnS0.2Se0.8 along the parallel direction.

The purpose of this study was to fabricate a low-immunogenicity fish collagen (FC) and bioactive nanohydroxyapatite (n-HA) enhanced poly­(lactide-co-glycolide) (PLGA) nanofibrous membrane for guided bone regeneration (GBR) via electrospinning. The physicochemical properties and morphology study revealed that FC and n-HA particles were homogeneously dispersed in the PLGA fibrous matrix. Notably, the formation of enhanced polymeric chain network due to the interaction between FC and PLGA significantly improved the tensile strength of the PLGA membrane. The incorporation of FC altered the degradation behavior of fibers and accelerated the degradation rate of the PLGA-based membranes. Moreover, the membranes exhibited favorable cytocompatibility with bone mesenchymal stem cells (BMSCs) and human gingiva fibroblasts (HGF) cells. More importantly, the optimized membrane satisfied the requirements of the ‘Biological evaluation of medical devices’ during the incipient biosafety evaluation. All the results indicate that this composite fibrous membrane exhibits significant potential for guided bone or tissue regeneration.

This work reveals the effectiveness of sodium doping in MnTe as a thermoelectric material fabricated by a facile method.

GeTe is a promising mid-temperature thermoelectric compound but inevitably contains excessive Ge vacancies hindering its performance maximization. This work reveals that significant enhancement in the dimensionless figure of merit (ZT) could be realized by defect structure engineering from point defects to line and plane defects of Ge vacancies. The evolved defects including dislocations and nanodomains enhance phonon scattering to reduce lattice thermal conductivity in GeTe. The accumulation of cationic vacancies toward the formation of dislocations and planar defects weakens the scattering against electronic carriers, securing the carrier mobility and power factor. This synergistic effect on electronic and thermal transport properties remarkably increases the quality factor. As a result, a maximum ZT > 2.3 at 648 K and a record-high average ZT (300-798 K) were obtained for Bi0.07Ge0.90Te in lead-free GeTe-based compounds. This work demonstrates an important strategy for maximizing the thermoelectric performance of GeTe-based materials by engineering the defect structures, which could also be applied to other thermoelectric materials.