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The natural mineral-based CoSbS compound has been identified as a potential candidate material for thermoelectric power generation. In this report, the solid solutions of CoSb 1−x S 1−x Se 2x (x ≤ 0.2) were constructed, and their electrical and thermal properties were studied at the temperatures ranging from 323 to 823 K. The results show that the dual doping of Se on Sb and S sites not only tunes the carrier concentration but also modifies the electronic structure, thereby optimizing the power factor of CoSbS effectively. Meanwhile, both the mass and the strain field fluctuation caused by the substitution of Se for both Sb and S strongly suppress the thermal conductivity of CoSbS, and finally make an enhanced zT ∼0.3 for CoSb 0.8 S 0.8 Se 0.4 at 823 K. In particular, the maximum averaged zT from 323 to 823 K in this study reaches ∼0.2, far exceeding the results of Se doping at single Sb or S site in CoSbS. These results indicate that dual doping at Sb and S sites via Se is an effective approach to make better thermoelectric performance for CoSbS. • Thermoelectric compound CoSbS with dual defects of Se Sb and Se S was constructed. • The carrier concentration and electronic structure of CoSbS were modified effectively by introducing of Se Sb and Se S defects. • An enhanced zT avg was obtained for CoSbS with Se Sb and Se S defects. [ABSTRACT FROM AUTHOR]

A group of MAX phases including Ti 2 AlC and Ti 2 AlN, are candidate reinforcements of Ag-based electrical contact materials. In this work, the interfacial reaction, resistivity, hardness and arc erosion resistance of Ag/Ti 2 AlX (X = C, N) were investigated comparatively. During the sintering of both Ag/Ti 2 AlX, Al deintercalated from Ti 2 AlX and Ag diffused into Ti 2 AlX. The interfacial reaction was mild in Ag/Ti 2 AlN while obvious in Ag/Ti 2 AlC. The first-principles calculation indicated that the higher vacancy formation energy of Al in Ti 2 AlN led to the mild reaction in Ag/Ti 2 AlN, which then resulted in a larger decrease in hardness and resistivity, as compared with Ag/Ti 2 AlC. Moreover, Ag/Ti 2 AlN showed superior arc erosion resistance, with less evaporation of Ag and oxidation of Ti 2 AlC. This were attributed to the lower vulnerability of mildly decomposed Ti 2 AlN, less resistance heat and easier heat dissipation, resulting from the superior electrical and thermal conductivity. • Interfacial reaction of Ag/Ti 2 AlX occurred by the diffusion of Ag into Ti 2 AlX and the outward diffusion of Al into Ag. • Higher vacancy formation energy of the Al of Ti 2 AlN contributed to less obvious interfacial reaction of Ag/Ti 2 AlN. • The interfacial reaction resulted in the increase of resistivity, and the stress relief led to the decline of hardness. • More intense reaction of Ag/Ti 2 AlC resulted in larger increase in resistivity and smaller decrease in hardness. • Mildly decomposed Ti 2 AlN and lower resistivity endowed the Ag/Ti 2 AlN with better arc erosion resistance. [ABSTRACT FROM AUTHOR]

N-type thermoelectric materials PbTe doped with iodine (PbTe 1−x I x , x = 0.0001, 0.0003, 0.0007 and 0.001) were synthesized by high pressure and high temperature method (HPHT). Thermoelectric properties of PbTe 1−x I x are investigated in the range of 300–600 K. The carrier concentration of PbTe prepared by HPHT is more sensitive to I content compared to that of the PbTe 1−x I x sample prepared by other methods. The resistivities and the absolute values of Seebeck coefficients for PbTe 1−x I x increase while the thermal conductivities decrease with increasing temperature. A large power factor of 39.1 μW/(cmK 2 ) at room temperature is obtained with the carrier concentration of 9.7 × 10 18 cm −3 , which is much higher than that of Sb and Bi doped PbTe with the same synthesizing conditions. The high power factor is attributed to the high Hall mobility and large effective mass. The maximum figure-of-merit, ∼0.71 @ 600 K, is obtained for the samples with the carrier concentration of 9.7 × 10 18 cm −3 . [ABSTRACT FROM AUTHOR]

Abstract: Non-stoichiometric Ag1−x Pb18SbTe20 (x =0, 0.2, 0.5, 0.7, 0.85) thermoelectric materials were prepared by high pressure method. The composition-dependent transport properties were studied at room temperature. The measurement results show that the carrier concentration and hall mobility of AgPb18SbTe20 could be tuned effectively by adjusting the content of Ag. The Seebeck coefficient and resistivity decrease with an increase of x. The maximum power factor of 2.3×10−3 Wm−1 K−2 is obtained at x =0.7, which is about 76% higher than that of the sample with stoichiometric composition. [ABSTRACT FROM AUTHOR]

Besides inferior conversion efficiency, the widespread application of thermoelectric materials currently faces the challenges of the rare and high cost of constituent elements, complex and time-consuming synthesis. Therefore, it is urgent to develop facile synthesized methods and high-performance thermoelectric materials consisting of elements with earth-abundance and low cost. Meeting above partial requirement, lead sulfide (PbS) recently was identified as a potential thermoelectric material to substitute current commercial PbTe. In this paper, a one-step high-pressure method was employed to facile and fast synthesis of PbS. Trace Cl doping tunes the carrier concentration of PbS effectively, which optimizes the electrical transport properties. Further PbSe alloying sharply reduces the thermal conductivity of PbS. Therefore, an enhanced zT ∼1.0 @ 700 K was obtained for PbS doped with 0.3 at% Cl and alloyed with 25 at% PbSe, which is comparable to the commercially applied PbTe. These results indicate that high-pressure combing with Cl-doping and PbSe-alloying provide a facile method and strategy to fabricate high-performance PbS-based thermoelectric materials. • Earth-abundant and low-cost thermoelectric compound PbS was facile and fast synthesized by one-step high pressure method. • Cl doping modulates the carrier concentration of PbS and thus optimizes its electrical properties at high temperature. • The chemical bond of PbS was weaken by PbSe alloying, which induces an enhanced Hall mobility near room temperature. • The thermal conductivity of PbS was suppressed sharply by PbSe alloying. • The enhanced zT max and zT avg achieve to 1.0 and 0.67 for PbS 0.747 Cl 0.003 Se 0.25 and PbS 0.497 Cl 0.003 Se 0.5, respectively [ABSTRACT FROM AUTHOR]

The structural changes of Y 2 Zr 2 O 7 under high pressure have been investigated by using angle-dispersive synchrotron X-ray powder diffraction up to 34 GPa at room temperature. A new pressure-induced phase transition from cubic ( Fm-3m ) structure to orthorhombic ( Pnma ) structure at 27.3 GPa is observed, and the phase transition is irreversible. The high-pressure orthorhombic ( Pnma ) phase has longer average cation–anion bonding distance than cubic ( Fm-3m ) structure which was proved by the increase of coordination number. [ABSTRACT FROM AUTHOR]