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Pseudo-ternary half-Heusler thermoelectric materials, which are formed by filling the B sites of traditional ternary half-Heusler thermoelectric materials of ABX with equal atomic proportions of various elements, have attracted more and more attention due to their lower intrinsic lattice thermal conductivity. High-purity and relatively dense Ti1−xNbx(FeCoNi)Sb (x = 0, 0.01, 0.03, 0.05, 0.07 and 0.1) alloys were prepared via microwave synthesis combined with rapid hot-pressing sintering, and their thermoelectric properties are investigated in this work. The Seebeck coefficient was markedly increased via Nb substitution at Ti sites, which resulted in the optimized power factor of 1.45 μWcm−1K−2 for n-type Ti0.93Nb0.07(FeCoNi)Sb at 750 K. In addition, the lattice thermal conductivity was largely decreased due to the increase in phonon scattering caused by point defects, mass fluctuation and strain fluctuation introduced by Nb-doping. At 750 K, the lattice thermal conductivity of Ti0.97Nb0.03(FeCoNi)Sb is 2.37 Wm−1K−1, which is 55% and 23% lower than that of TiCoSb and Ti(FeCoNi)Sb, respectively. Compared with TiCoSb, the ZT of the Ti1−xNbx(FeCoNi)Sb samples were significantly increased. The average ZT values of the Nb-doped pseudo-ternary half-Heusler samples were dozens of times that of the TiCoSb prepared using the same process. [ABSTRACT FROM AUTHOR]

In this study, effects of different pressing processes on the microstructure and thermoelectric properties of TiNiSn1-xTex Half-Heusler alloy prepared by microwave method were investigated. TiNiSn1-xTex Half-Heusler alloys prepared by microwave synthesis-warm pressing-microwave sintering process had relatively higher density than those of samples prepared by microwave synthesis-cold pressing-microwave sintering (MCM) process. The XRD results showed that the diffraction peaks of TiNiSn1-xTex samples slightly shifted to the large angle direction because of the Te substitution on the Sn sites, and the intensity of impurity peak decreased after microwave sintering. Although the density of TiNiSn1-xTex samples prepared by MCM process was lower, the thermoelectric performance of TiNiSn0.99Te0.01 sample was significantly improved, which resulted from the decrease of resistivity and thermal conductivity due to the Te-doping. The thermal conductivity of TiNiSn0.99Te0.01 was within 1.21–1.61 Wm - 1 K - 1 over the whole temperature range, and its thermoelectric figure of merit ZT was the best. [ABSTRACT FROM AUTHOR]

Ternary Cu3SbSe4 thermoelectric material with a diamond-like structure exhibits good thermoelectric performance in the middle-temperature region. In this study, Cu2.98Co0.02SbSe4 material with intrinsically low thermal conductivity was prepared by a melting–ball milling–hot pressing process. The maximum zT value for the Cu2.98Co0.02SbSe4 sample was 0.7 at 650 K, which was about 190% higher than that of the pristine sample. The improvement in thermoelectric performance was ascribed to the realization of multi-scale features induced by ball milling. It was found that multiple scattering centers of phonons were formed via interfacial engineering, including dislocations, nano-holes and grain boundaries, which offers an applicable pathway for the reduction of lattice thermal conductivity. [ABSTRACT FROM AUTHOR]

The ternary Cu3SbSe4 thermoelectric material with diamond-like structure exhibit good electrical properties in the middle-temperature region. Forming co-alloying solid solutions has long been considered as an effective strategy for decoupling electrical conductivity and Seebeck coefficient. In this study, the Cu3-xAgxSb1-yTeySe4 (x = 0–0.1; y = 0–0.05) materials were fabricated by melting-ball milling-hot pressing process. The influences of configurational entropy on the microstructure and thermoelectric properties of Cu3SbSe4 were evaluated. It was found that the electrical conductivity of Cu2.9Ag0.1Sb0.95Te0.05Se4 was about 200% higher than that of pure sample due to the slightly configurational entropy tuning. Moreover, multiscale free path phonons of Cu2.9Ag0.1Sb0.95Te0.05Se4 can be greatly scattered and the lattice thermal conductivity decreased from 3.0 to 2.1 Wm−1 K−1 at 300 K via lattice-distortion effect. The maximum zT value of 0.84 was obtained at 650 K for the Cu2.9Ag0.1Sb0.95Te0.05Se4 sample. These results displayed the multiple effects on thermoelectric transport during the formation of co-alloying solid solutions. [ABSTRACT FROM AUTHOR]

Nanosized C60 powder was sufficiently incorporated with Cu2GeSe3 powder by ball milling and C60/Cu2GeSe3 composites were prepared by spark plasma sintering. C60 distributed uniformly in the form of clusters and the average size of cluster was lower than 1 μm. With the addition of C60 increasing, the electrical resistivity and Seebeck coefficient of C60/Cu2GeSe3 composites increased while the thermal conductivity decreased significantly which resulted from the phonon scattering by C60 clusters locating on the grain boundaries of Cu2GeSe3 matrix. The maximum ZT of 0.20 was achieved at 700 K for 0.9% C60/Cu2GeSe3 sample. [ABSTRACT FROM AUTHOR]

Forming co-alloying solid solutions has long been considered as an effective strategy for improving thermoelectric performance. Herein, the dense Cu2−x(MnFeNi)xSe (x = 0–0.09) with intrinsically low thermal conductivity was prepared by a melting-ball milling-hot pressing process. The influences of nanostructure and compositional gradient on the microstructure and thermoelectric properties of Cu2Se were evaluated. It was found that the thermal conductivity decreased from 1.54 Wm−1K−1 to 0.64 Wm−1K−1 at 300 K via the phonon scattering mechanisms caused by atomic disorder and nano defects. The maximum zT value for the Cu1.91(MnFeNi)0.09Se sample was 1.08 at 750 K, which was about 27% higher than that of a pristine sample. [ABSTRACT FROM AUTHOR]

Abstract: Ga-filled and Te-doped CoSb3 skutterudites were synthesized by a melt-quench-anneal-hot-press sintering method, and their thermoelectric properties were investigated from 300 to 800 K. The filling fraction of Ga in doped skutterudite is up to x = 0.2 and the results of XRD and lattice parameter are in agreement with the change of filling fraction. When the Ga content x = 0.3, there was the second phase GaSb existing in the skutterudite. All Ga x Co4Sb11.7Te0.3 samples were the N-type conduction and the electrical conductivity increased with the content of Ga increasing. Thermal conductivity of Ga x Co4Sb11.7Te0.3 decreased markedly due to the phonon scattering, which resulted from the filling of Ga atoms. The highest thermoelectric figure of merit ZT = 0.6 is achieved at 650 K in the Ga0.3Co4Sb11.7Te0.3 compound. [Copyright &y& Elsevier]

In this study, the Cu–Te alloy ribbons containing nanocrystalline structures were prepared by melt spinning (MS), and were composed of Cu2−xTe, Cu2Te, Cu3−xTe, and CuTe phases. Crystal grains on both sides of the ribbons were uniformly distributed and the grain size of the contact surface was about 400 nm. The Cu–Te powder was incorporated into the Cu2SnSe3 powder by the ball milling process and the Cu–Te/Cu2SnSe3 thermoelectric composite was prepared by spark plasma sintering (SPS). With the amount of Cu–Te powder increasing, the carrier concentration of the Cu–Te/Cu2SnSe3 composite increased, while the carrier mobility and electrical conductivity initially increased and then decreased. Compared to the Seebeck coefficient of the Cu2SnSe3 matrix, the Seebeck coefficient of the Cu–Te/Cu2SnSe3 samples increased slightly. Moreover, the Cu–Te/Cu2SnSe3 composites had lower thermal conductivity and lattice thermal conductivity over the whole temperature range. The lattice thermal conductivity of the 0.8 vol.% Cu–Te/Cu2SnSe3 composite achieved the lowest value of 0.22 W/m·K, which was 78% lower than that of the Cu2SnSe3 matrix. The maximum figure of merit of the 0.8 vol.% Cu–Te/Cu2SnSe3 composite was 0.45 at 700 K. [ABSTRACT FROM AUTHOR]

In this study, n-type Pd-doped ZrCo1-xPdxBi (x = 0, 0.03, 0.06, 0.09) half-Heusler samples were prepared by arc-melting and rapid hot-pressing sintering. The thermoelectric properties of ZrCo1-xPdxBi samples were analyzed and discussed. The results showed that the electrical properties of ZrCo1-xPdxBi, including electrical conductivity and the Seebeck coefficient, increase due to the substitution of Pd on Co site. The lattice thermal conductivity of ZrCo1-xPdxBi is markedly decreased because of the Pd/Co substitution. A minimum κL of 5.0 W/mK for ZrCo0.91Pd0.09Bi is achieved at 800 K. The figure of merit of ZrCo1-xPdxBi is boosted due to the depressed lattice thermal conductivity and the improved power factor. The highest value of figure of merit reaches 0.23 for ZrCo0.97Pd0.03Bi half-Heusler compound at 800 K. [ABSTRACT FROM AUTHOR]

Recently, the cubic SnSe with multiple valleys and low thermal conductivity has become the focus of current research and receives extensive attention worldwide. However, the cubic SnSe is difficult to exist stably at normal temperature and pressure. In this work, the cubic rock-salt SnSe samples were successfully stabilized at room temperature by AgBiTe 2 alloying. Microstructure and thermoelectric properties of the Sn 1–2 x (AgBi) x Se 1–2 x Te 2 x (x = 0, 0.10, 0.15, 0.20, 0.25, 0.30) were studied systematically. With the increase of AgBiTe 2 addition, the crystal structure of SnSe gradually transformed from orthorhombic to cubic phase. Due to the doping of heterogeneous atoms and the phase structural transformation, the carrier concentration and carrier mobility of Sn 1–2 x (AgBi) x Se 1–2 x Te 2 x were optimized, thus the electrical properties were significantly enhanced. An obviously enhanced zT max of 0.70 at 750 K and a zT ave of 0.29 (300–750 K) were achieved in Sn 0.50 (AgBi) 0.25 Se 0.50 Te 0.50. In addition, the mechanical properties of Sn 1–2 x (AgBi) x Se 1–2 x Te 2 x were also strengthened. A higher Vickers hardness of ∼1.8 GPa was obtained in Sn 0.40 (AgBi) 0.30 Se 0.40 Te 0.60. • The cubic rock-salt structure of SnSe were stabilized successfully by AgBiTe 2 alloying. • The electrical properties of Sn 1–2 x (AgBi) x Se 1–2 x Te 2 x were optimized by phase structural transformation. • A maximum zT of 0.70 was obtained in Sn 0.50 (AgBi) 0.25 Se 0.50 Te 0.50 at 750 K. • The Vickers hardness increased from ∼0.9 GPa for the pristine SnSe to ∼1.8 GPa for the Sn 0.40 (AgBi) 0.30 Se 0.40 Te 0.60 sample. [ABSTRACT FROM AUTHOR]

• Nano-SnTe is an excellent candidate for incorporating into the Cu 3 SbSe 4 matrix. • The electrical conductivity was significantly improved by tuning the carrier concentration. • The addition of nano-SnTe can depress the lattice thermal conductivity. Cu 3 SbSe 4 is a ternary Cu-based compound with diamond-like structure, which has broad prospects due to its relatively low thermal conductivity and great potential for improving electrical properties. In this study, nano-SnTe was introduced into Cu 3 SbSe 4 matrix by mechanical ball milling and the bulk SnTe/Cu 3 SbSe 4 composites were fabricated using rapidly hot-pressing sintering. The phase composition and microstructure of SnTe/Cu 3 SbSe 4 composites were characterized. The results showed that the added SnTe particles were mainly distributed at the grain boundary of Cu 3 SbSe 4. The addition of nano-SnTe tuned the carrier concentration and improved the electrical conductivity of Cu 3 SbSe 4 greatly. The carrier concentration and electrical conductivity of 4.00%SnTe/Cu 3 SbSe 4 composite at room temperature were 1.68 × 1020 cm−3 and 3.75 × 104 S m−1, respectively. Moreover, the existence of nano-SnTe particles decreased the thermal conductivity of SnTe/Cu 3 SbSe 4 composites obviously. The maximum zT of 0.71 was obtained for the 2.00%SnTe/Cu 3 SbSe 4 sample at 650 K, which was 3.4 times higher than that of pure Cu 3 SbSe 4. [ABSTRACT FROM AUTHOR]