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Abstract: In this article, a rapid and cost-effective melt spinning (MS) subsequently combined with a spark plasma sintering (SPS) process was utilized to prepared n-type Bi2(Te1−x Se x )3 (x = 0.0–1.0) solid solutions from high purity single elemental chunks. The substitution of tellurium by selenium has significant impacts on the electrical and thermal transport properties of the Bi2(Se x Te1−x )3 compounds in a manner which can be well understood using a valence bond rule and the corresponding change in band gap. Furthermore, the selenium substitution effectively adjusts the carrier density allowing an optimum value of ∼5 × 10−19 cm−3. As a result, a maximum ZT of 1.05 at 420 K was achieved for the Bi2(Se0.2Te0.8)3 sample which also shows an improved average ZT of ∼0.97 in the entire measurement temperature range. By adopting the same p-type legs, the module fabricated by the MS-SPS Bi2(Se0.2Te0.8)3 material which acts as n-type legs shows ∼10% enhancement in thermoelectric conversion efficiency compared with the module fabricated by n-type zone melted ingots. [Copyright &y& Elsevier]

Abstract Oxide materials are of current interest as high-temperature thermoelectrics in the automotive and manufacturing energy-harvesting sectors due to high chemical robustness, low toxicity and low cost. Driven by a need to improve the thermoelectric performance of n-type oxides to the level of p-type analogues, ceramics and composites based on donor-doped SrTiO 3 are considered as a promising material. Here Nb-doped SrTiO 3 with Nb content of 10 and 15% as well as Sr/(Nb + Ti) ratio of 1.00 and 0.98 was mixed with 0.6 wt. % of graphene oxide (GO) prepared by Hummer-based method and conventionally sintered in atmosphere of H 2 /N 2 to reduce both Nb-doped SrTiO 3 and GO. Addition of reduced GO in combination with introduction of Sr vacancies provides a synergistic effect of fastening charge transport and thereby increasing electrical conductivity σ and suppressing the thermal conductivity κ. These factors, together with a moderate Seebeck coefficient S , result in a high power factor PF = S 2 × σ up to ∼1.98 mW/(K2m) and thermoelectric figure of merit ZT = PF × T / κ up to 0.29. These findings offer further prospects for seeking high performance SrTiO 3 -based thermoelectrics by modification with reduced GO. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Abstract This work aims to explore zirconium as a possible dopant to promote thermoelectric performance in bulk ZnO-based materials, both within the single-doping concept and on simultaneous co-doping with aluminum. At 1100–1223 K mixed-doped samples demonstrated around ∼2.3 times increase in ZT as compared to single-doped materials, reaching ∼0.12. The simultaneous presence of aluminum and zirconium imposes a synergistic effect on electrical properties provided by their mutual effects on the solubility in ZnO crystal lattice, while also allowing a moderate decrease of the thermal conductivity due to phonon scattering effects. At 1173 K the power factor of mixed-doped Zn 0.994 Al 0.003 Zr 0.003 O was 2.2–2.5 times higher than for single-doped materials. Stability tests of the prepared materials under prospective operation conditions indicated that the gradual increase in both resistivity and Seebeck coefficient in mixed-doped compositions with time may partially compensate each other to maintain a relatively high power factor. [ABSTRACT FROM AUTHOR]

Abstract: β-Zn4Sb3 compounds doped with minute amounts of Cd were synthesized by the MS-SPS technique, which involves melt spinning (MS) followed by spark plasma sintering (SPS), and the microstructures, thermoelectric and thermodynamic properties were systematically characterized. The non-equilibrium MS-SPS technique generates multi-scale nanostructures in the MS-prepared ribbon-shape samples and the resulting compacted bulk materials. These unique multiple nanostructures result in substantial reductions in lattice thermal conductivities, particularly for samples with a large number of ZnSb nanodots with sizes of 10–30nm. Meanwhile, Cd-doping remarkably improves the electrical properties of the (Zn1− x Cd x )4Sb3 compounds by a slight decrease in electrical conductivity and an apparent enhancement of the Seebeck coefficient. Therefore, the dimensionless figure of merits are significantly improved and the maximum value reaches ∼1.30 for the (Zn0.99Cd0.01)4Sb3 sample at 700K, representing ∼13% and ∼23% improvements compared with the undoped MS-SPS sample and the 1% Cd-doped melting ingot, respectively. In particular, this value shows no degradation after 10 heat cycles from 300 to 700K or 30h annealing at 680K in vacuum, whereas the ZT of neat sample decreases by ∼20% to a relatively low value of ∼1.0 after 30h annealing. The enhanced thermal stability of ZT along with the suppressing effect on the low-temperature α–β phase transition clearly indicates a large improvement in thermodynamic stability as a result of minute Cd-doping. All the above-mentioned benefits make the minute Cd-doped β-Zn4Sb3 compound prepared by the MS-SPS technique a promising candidate for mid-range temperature thermoelectric power generation applications. [Copyright &y& Elsevier]