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In practical application of microgrid cluster, the lack of full detailed information cause the failure of dynamic modeling. Although some data-driven black-box modeling method can tackle this problem, insufficient usage of prior known physical information may reduce the modeling accuracy. To tackle this challenge, a hybrid physical-data-driven method is proposed for the dynamic behavior modeling of microgrid cluster. Motivated by the equivalence of recurrent neural network (RNN) and differential equations, the differential-algebraic equations (DAEs) of unknown part are represented by gate recurrent unit (GRU) based neural network. The DAEs of prior known physical stage are embedded into the proposed neural network, which avoid unnecessary model training of prior known section and improving the modeling efficiency. At first, the basic idea of RNN based dynamic modeling is explained. Then, the modeling guidelines including data preparation and parameter design are suggested. Finally, the effectiveness of the proposed method is confirmed by a test system formed by three microgrids under grid fault and operating point changing conditions.

The reaction of MnTe with AgSbTe2 in an equimolar ratio (ATMS) provides a new semiconductor, AgMnSbTe3. AgMnSbTe3 crystallizes in an average rock-salt NaCl structure with Ag, Mn, and Sb cations statistically occupying the Na sites. AgMnSbTe3 is a p-type semiconductor with a narrow optical band gap of ∼0.36 eV. A pair distribution function analysis indicates that local distortions are associated with the location of the Ag atoms in the lattice. Density functional theory calculations suggest a specific electronic band structure with multi-peak valence band maxima prone to energy convergence. In addition, Ag2Te nanograins precipitate at grain boundaries of AgMnSbTe3. The energy offset of the valence band edge between AgMnSbTe3 and Ag2Te is ∼0.05 eV, which implies that Ag2Te precipitates exhibit a negligible effect on the hole transmission. As a result, ATMS exhibits a high power factor of ∼12.2 μW cm-1 K-2 at 823 K, ultralow lattice thermal conductivity of ∼0.34 W m-1 K-1 (823 K), high peak ZT of ∼1.46 at 823 K, and high average ZT of ∼0.87 in the temperature range of 400-823 K.

Polycrystalline sulfides are promising thermoelectric materials because of their abundance, non-toxicity, and low cost. However, their low thermoelectric performance hampers their possible large-scale industrial application. In this work, Cu self-doping in Cu2+xZn1−xSnS4, prepared using a simple processing route, realizes the decoupling of thermal and electric transport as follows. The additional copper ions occupy Zn sites and provide more carriers, which leads to excellent hole conductivity. Moreover, when x is above 0.125, the content of Cn/Zn disordered sites is beyond the percolation threshold (∼0.3) of thermal diffusivity. A maximum power factor (450 μW m−1 K−2) is obtained for Cu2.125Zn0.875SnS4. Combined with ultra-low specific heat below the theory predicted minimum for structural disordering on the copper and zinc sites, the κ of the material reduces to 0.22 W m−1 K−1 at 773 K, which is minimum in thermoelectric materials up to now. Moreover, hot forging (deformation strain ∼64% and maximum of displacement rate ∼18 mm min−1), a dynamic plastic deformation process, was employed to produce defects on different length scales (point defects, dislocations, stacking faults and deformation twins), that optimize the power factor and lattice thermal conductivity. Based on the above synergistic effects, a high ZT value of 1.1 has been achieved in Cu2.125Zn0.875SnS4 ceramics, and there is 18-fold increase in ZT value compared with that of conventionally processed intrinsic Cu2ZnSnS4.

In this work, earth abundant CaI2 compound has been applied to regulate the thermoelectric performance of SnTe by codoping in both the anion and cation sites for the first time. The carrier concentration has been effectively tuned to a reasonable range due to the electron donor nature of ITe+ point defects; on the other hand, the Seebeck coefficient has been significantly enhanced because of the resulted valence band convergence and band gap enlargement. More importantly, the phonon and carrier scattering have been tailored tactically, and a relatively high power factor with a significantly lowered thermal conductivity have been achieved simultaneously. In consequence, an enhanced figure of merit ZT ∼1.2 at 873 K was attained in the SnTe-3% CaI2 sample.

As a tellurium- and lead-free compound, Cu3SbSe4 is a promising thermoelectric material with relatively high Seebeck coefficient and low thermal conductivity. Here, an effective strategy of weakening p–d hybridization was proposed and demonstrated to enhance the thermoelectric properties for Cu3SbSe4via Ag substitution. This strategy performs a multiple role in high thermoelectric performance, boosting both maximum and average ZT: (1) increase the hole concentration due to the weakened Cu–Se bonding, (2) enlarge the energy gap Eg, putting off the bipolar diffusion, (3) increase the density of states effective mass, and (4) reduce the lattice thermal conductivity mainly due to the large strain fluctuations. As a consequence, a peak ZT ∼ 0.9 at 623 K and a high average ZT above 0.5 for the range 298–623 K can be achieved in a Cu2.85Ag0.15SbSe4 sample. This study provides a new strategy of softening p–d hybridization to boost the thermoelectric performance of Cu3SbSe4 by the synergistic regulation of charge carrier and phonon transports, which is also a meaningful guidance to achieve high thermoelectric performance in other copper-based chalcogenides.

Here, we have systematically explored the effects of rare-earth metal La doping on the thermoelectric properties of PbSe. The results show that i) La is an effective n-type dopant to regulate the carrier concentration, ii) La-doping can flatten the conduct band of PbSe to increase the effective mass and thus the improved Seebeck coefficient. Under the combined regulation of carrier concentration and band structure, a high average power factor of 1650 µW.m−1K−2 among 300-873 K is obtained. Meanwhile, the lattice thermal conductivity will be reduced due to the extra point defect scattering and the depressed bipolar conduct by La doping. Finally, a peak ZT of 0.96 and a high average ZT of 0.71 among 300-873 K are achieved in the 0.125% La doped sample. The multiple beneficial effects stemming from rare-earth metal La doping is an important finding that will stimulate new exploration toward high-performance n-type PbSe-based thermoelectric materials.

The quality of interface between the electron transport layer (ETL) and perovskite is very crucial to the photovoltaic performance of a flexible perovskite solar cell fabricated under low-temperature process. This work demonstrates a room temperature ionic liquid modification strategy to the interface between ZnO layer and MAPbI3 film for high performance flexible perovskite solar cells based on a PET substrate. [BMIM]BF4 ionic liquid modification can significantly improve the surface quality and wettability of the ZnO ETL, thus greatly increase the charge mobility of ZnO ETL and improve the crystalline of perovskite film based on it. Moreover, the dipolar polarization layer among the ZnO ETL with perovskite, built by modification, can adjust the energy level between the ZnO ETL and perovskite and facilitates the charge extraction. Therefore, an overall power conversion efficiency (PCE) of 12.1% have been achieved under standard illumination, it increases by 1.4 times of the flexible perovskite solar cells on a pristine ZnO ETL.

It is a challenge to optimize the coupled electrical and thermal transport properties of a thermoelectric material simultaneously. Here, the enhancement of overall thermoelectric properties in Cu 3 SbSe 4 has been demonstrated through Te substitution. The results display that the simultaneous optimization of the Seebeck coefficient, electrical conductivity and thermal conductivity is realized after Te-doping and thus yielding considerable enhancements in ZT values in the whole temperature range as comparison to that of pristine Cu 3 SbSe 4 . In Te-doped Cu 3 SbSe 4 system, the reduction of electrical resistivity is due to the narrowed bandgap; the enhanced Seebeck coefficient stems from the increased density of states near the Fermi level; and the suppressed thermal conductivity is related to the introduced phonon blocking from point defect scattering or softening of chemical bond interaction. This work can also offer a referential route to boost the overall thermoelectric properties by isovalent doping with heavy element for other thermoelectric materials.

The effect of Al-, Ga-, and In-doping on the thermoelectric (TE) properties of Cu3SbSe4 has been comparatively studied on the basis of theoretical prediction and experimental validation. It is found that tiny Al/Ga/In substitution leads to a great enhancement of electrical conductivity with high carrier concentration and also large Seebeck coefficient due to the preserved high band degeneracy and thereby a remarkably high power factor. Ultimately, coupled with the depressed lattice thermal conductivity, all three elements (Al/Ga/In) substituted samples have obtained a highly improved thermoelectric performance with respect to undoped Cu3SbSe4. Compared to the samples at the same Al/In doping level, the slightly Ga-doped sample presents better TE performance over the wide temperature range, and the Cu3Sb0.995Ga0.005Se4 sample presents a record high ZT value of 0.9 among single-doped Cu3SbSe4 at 623 K, which is about 80% higher than that of pristine Cu3SbSe4. This work offers an alternative approach to boost the TE properties of Cu3SbSe4 by selecting efficient dopant to weaken the coupling between electrical conductivity and Seebeck coefficient.

High-pressure in situ angle dispersive X-ray diffraction (ADXRD) measurements were performed on the charge-density-wave (CDW) material In 4 Se 3 up to 48.8 GPa. Pressure-induced structural changes were observed at 7.0 and 34.2 GPa, respectively. Using the CALYPSO methodology, the first high-pressure phase was solved as an exotic Pca 2 1 structure. The compressional behaviors of the initial Pnnm and the Pca 2 1 phases were all determined. Combined with first-principle calculations, we find that, unexpectedly, the Pnnm phase probably experiences twice electronic topological transitions (ETTs), from the initial possible CDW state to a semimetallic state at about 2.3 GPa and then back to a possible CDW state at around 3.5 GPa, which was uncovered for the first time in CDW systems. In the both possible CDW states, pressure provokes a decrease of band-gap. The observation of a bulk metallic state was ascribed to structural transition to the Pca 2 1 phase. Besides, based on electronic band structure calculations, the thermoelectric property of the Pnnm phase under compression was discussed. Our results show that pressure play a dramatic role in tuning In 4 Se 3 's structure and transport properties.

The present work demonstrates the effect of Mn, Fe, Ni and Cu doping on the orientation, microstructure, electrical and thermal transport properties of Bi 0.5 Sb 1.5 Te 3 ingots prepared under a 2 T magnetic field. The comparative results show that the c-axis is inclined to perpendicular to magnetic field in the ferromagnetic ions (Fe and Ni) doped samples, while is inclined to parallel to magnetic field in the non-magnetic Cu and paramagnetic Mn doped samples; in addition, the growth of eutectic structure is disturbed intensively in the ferromagnetic ions doped samples, resulting in scattered arrangement of Te trips, BST Ⅱ nano-rods and nano-scale Te crystals. As a consequence, the thermal conductivity in the ferromagnetic ions doped samples are sharply decreased owing to the enhanced scattering of holes and phonons by the hierarchical architecture of phase boundaries, grain boundaries, BST Ⅱ nano-rods even sub-grain boundaries, and a high ZT of ∼1.6 at 323 K was obtained in the ferromagnetic ions doped samples.

Polycrystalline Mn1-xCuxTe (x = 0, 0.025, 0.05, 0.075) thermoelectric materials were prepared by a combined method of melt-quenching and hot press. The effect of Cu doping on the electrical resistivity, band gap, the Seebeck coefficient and thermal conductivity was investigated. The power factors of the Cu-doped samples increase greatly due to the decrease of electrical resistivity and the higher Seebeck coefficient in high temperatures. In addition, the thermal conductivities of the Cu-doped samples also reduce due to the extra phonon scattering from the point defects introduced by Cu doping. As a result, the thermoelectric performance of MnTe is greatly enhanced, and a maximum ZT value of ∼0.55 in the Mn0.925Cu0.075Te sample at 773 K is achieved, which is 35% greater than that of the pristine MnTe sample.

In doped Cu3Sb1-xInxSe4 (x = 0, 0.002, 0.003 and 0.004) compounds have been fabricated via a combined process of melting-pulverization-hot pressing. Effect of In doping on their thermoelectric properties have been explored and it reveals that In occupies the site of Sb and plays a role of acceptor dopant. With the increase of In doping content, the electrical resistivity and Seebeck coefficient decrease, and the power factor is obviously improved at elevated temperature compared with un-doped Cu3SbSe4. Meanwhile, the thermal conductivity is also reduced due to the extra phonon scattering by point defects introduced by In doping. As a consequence, a maximum ZT value of 0.50 (at 648 K) is obtained for the doped sample (x = 0.003), which is about 47% higher than that of the un-doped Cu3SbSe4. Keywords: Cu3SbSe4, In-doping, Thermoelectric properties

We studied the effect of doping with Bi on the thermoelectric properties of SnTe-based materials. Doping with Bi reduced the density of holes and increased the Seebeck coefficient over a wide temperature range as a result of modulation of the carrier concentration and an increase in the density of states effective mass. The lattice thermal conductivity was also greatly reduced as a result of the wide frequency range of phonon scattering by multiscale architectures derived from Bi doping. A maximum ZT value of c. 1.1 at 873 K was obtained in Sn0.94Bi0.06Te, an enhancement of 165% compared with the undoped sample.

Recently, research interests in p-type skutterudites are focused on multi-filling in the intrinsic void sites of Fe4−xMxSb12. The four-membered antimony rings, another important structural feature of p-type skutterudites, seem to be overlooked. In this study, Te has been employed to substitute Sb in single-filled p-type Ce0.9Fe3.75Ni0.25Sb12 skutterudite and a systematic investigation has been carried out into the doping effect of Te on the microstructure and thermoelectric properties of this material. With an increase of Te doping, the electrical resistivity decreases due to the increase of hole concentration and the gradual decrease of mobility; while the density of state effective mass increases rapidly with the increase of hole concentration due to the intrinsic multiple bands effects, thus the Seebeck coefficient increases slightly. In addition, Te doping on Sb sites changes the valance electron balance and results in the formation of microscale γ-Ce and nanoscale CeTe2 compound. These microscale and nanoscale precipitates work together with the atomic scale distortion of Sb4 rings by the substitution of Te for Sb, could scatter phonons with a wide range of frequency thus result in a significant reduction of the lattice thermal conductivity. Therefore the thermoelectric performance has been enhanced greatly, and a maximum ZT value of 1.0 at 773 K was obtained for the Ce0.9Fe3.75Ni0.25Sb11.9Te0.1 sample.

SnTe is a promising alternative of the moderate-temperature thermoelectric material PbTe owing to its earth-abundant and nontoxic nature. However, its several shortcomings, such as small Seebeck coefficient thus poor power factor and upper lattice thermal conductivity, which have restricted overall thermoelectric performance of SnTe. In this scenario, an effective approach to decouple electrical parameters of electrical conductivity and Seebeck coefficient typified by introducing Vanadium (V) interstitial defects, realizing an ultrahigh power factor and a reduction in lattice thermal conductivity has been presented in SnTe system. Concretely, the V-interstitial defects caused by alloying V with SnTe enable lower formation energy of intrinsic Sn vacancies and holistic weak chemical bonding surrounded by Sn atom, thereby improving carrier density and the overall electrical conductivity. Meanwhile, the high-temperature Seebeck coefficient was significantly enhanced due to the increased valence band convergence and in-situ self-doping effect induced by V-interstitials. Moreover, beneficial from the hierarchical crystal defects and microstructure, the independent lattice thermal conductivity had been greatly reduced to its amorphous limit of ~0.4 Wm−1K−1. In virtue of these multiple functions of V-interstitials, a record-high power factor of ~37.4 μWcm−1K−2 by single element alloying and an enhanced zT value of ~1.3 at 873 K, combined with a calculated engineering output power density ~263 Wcm−2, were achieved in the Sn0.98V0.02Te sample. Conclusively, this work provides an ingenious way to further maximize its electrical performance despite the already-high electrical conductivity of SnTe, impelling the potential application of SnTe for high output power density, and this may also apply to other highly conductive thermoelectric systems.

Bulk Bi0.4Sb1.6Te3 materials with ZnO nanoinclusions have been fabricated by mechanical alloying and plasma-activated sintering. The effects of ZnO addition on the microstructure and thermoelectric performance of the Bi0.4Sb1.6Te3 materials have been studied in detail. Scanning electron microscopy (SEM) observation confirms that the ZnO particles distribute in the Bi0.4Sb1.6Te3 matrix homogeneously until the content is over 0.5 wt.%. The resistivity and Seebeck coefficient of the samples increase slightly with the ZnO content, while the thermal conductivity is reduced effectively by addition of ZnO nanoparticles due to extra phonon scattering at ZnO nanoinclusions, and a maximum ZT of 1.21 is achieved in the sample with 0.3 wt.% ZnO at 373 K.

Skutterudites have attracted a lot of attention because of the intrinsic voids in their crystal structure. However, another important structural feature of p-type skutterudites seems to have been ignored, namely the nearly square four-membered antimony rings. To explore the influence of substitution of Te for Sb on the microstructure and thermoelectric properties, a series of p-type skutterudites with composition CeFe4Sb12−xTex with x = 0, 0.1, and 0.2 have been synthesized. The electrical resistivity decreases while the Seebeck coefficient increases with Te doping. In addition, due to disturbance of the Sb4 rings and extra phonon scattering by nanopores, the lattice thermal conductivity is reduced. The thermoelectric figure of merit for the CeFe4Sb11.9Te0.1 compound reaches 0.76 at 773 K, being about 61% higher than that of the CeFe4Sb12 sample.

In this work, Na-doped BiCuSeO thermoelectric materials have been prepared and the effect of Na doping on their microstructure and thermoelectric properties has been studied. When the doping content is less than 6%, all Na+ can dissolve into the matrix and substitute for Bi3+ sites and play a role of acceptor; when the content is above 6%, the substitution saturates and excessive doping results in the formation of Na2CO3 and Na2SeO3 secondary phases. On the one hand, the doping of Na+ for Bi3+ can significantly improve the electrical properties due to the significant increase of carrier concentration. Furthermore, the phonon and total thermal conductivity also decrease with Na doping because of the dual phonon scattering by the point defects and secondary phases both resulting from Na+ doping. As a result, the thermoelectric performance is enhanced, and a maximum ZT value of 0.97, which is approximately triple that of the undoped BiCuSeO, is achieved at 873 K for the Bi0.92Na0.08CuSeO sample.

Since the lattice thermal conductivity of n-type multi-filled skutterudites have been reduced below 1 W (mK−1), the development of new strategies that can further enhance the power factor while maintaining the low thermal conductivity is highly desired. In this paper, we conducted a pioneering work by introducing a “core–shell” microstructure into Yb single-filled skutterudite thermoelectric materials to realise this purpose. The “core–shell” structure formed by the thermal diffusion of well dispersed Ni nanoparticles in the Yb0.2Co4Sb12 powder during hot pressing is composed of the normal “core” grains surrounded by Ni-rich nanograin “shells”. The electrical resistivity is greatly reduced due to the increase in both carrier concentration and mobility. However, the Seebeck coefficient first increases due to the increased density of states at the Fermi energy and then decreases gradually. As a consequence, the power factor is remarkably increased for the samples with the addition of Ni nanoparticles. In addition, the lattice thermal conductivity is also reduced by the extra phonon scattering introduced by the “core–shell” microstructure. The concomitant effects enable a maximum ZT of 1.07 for the 0.2 wt% Ni sample at 723 K.

The catalytic properties of Ni-25 at% Al (Ni25Al) nanoparticles fabricated by arc plasma evaporation toward methanol decomposition were studied at temperatures ranging from 513 to 753 K. The Ni25Al nanoparticles showed much higher activity than gas atomized Ni25Al powders. They showed a high degree of selectivity for methanol decomposition into H 2 and CO. Side reactions such as methanation and water-gas shift reaction were suppressed to a high temperature of 673 K, which is hardly achieved for common Ni catalysts. Detailed characterization of the Ni25Al nanoparticles showed that they were composed of Ni, Ni 3 Al, and Al 2 O 3 phases with Ni and Al oxides on the surface of the Ni and Ni 3 Al phases. The Ni oxides were reduced to Ni phase by a hydrogen reduction prior to methanol decomposition, while the Al oxides remained unchanged. It is supposed that the Ni phase provided the active sites for methanol decomposition, and the Ni 3 Al and Al 2 O 3 phases acted as supports for the Ni phase. Probably the Ni 3 Al and Al 2 O 3 phases provided good resistance to agglomeration of the Ni phase during the reaction, which might contribute to maintain the high catalytic performance of the nanoparticles for methanol decomposition.

The catalytic activity of Ni-Al (Ni25Al) nanoparticles fabricated by thermal plasma evaporation was examined for methanol decomposition and CO oxidation. The nanoparticles exhibited high activity for both reactions. Characterization of the nanoparticles revealed that the fabricated nanoparticles were mainly comprised of Ni and Ni3Al phases. During CO oxidation, the Ni phase was oxidized to NiO, while the Ni3Al phase remained unchanged. The NiO phase is supposed to serve as the active sites for CO oxidation. In contrast, during methanol decomposition, no obvious oxidation was observed for both Ni and Ni3Al phases. The Ni and Ni3Al phases are supposed to contribute to the high activity for methanol decomposition.

A cost-effective and rapid mechanical alloying method was used to prepare Yb-stuffed and Te-substituted CoSb3 to study the thermoelectric properties of this material. Yb rattles inside the cage-like structure of CoSb3 which effectively reduces the phonon mean free path and results in a lattice thermal conductivity comparable to those of costly nanostructured CoSb3 materials. A very low lattice thermal conductivity of 1.17 W m−1 K−1 at ∼550 K was obtained. A zT value of ∼0.7 was reported at 600 K due to the very low lattice thermal conductivity.

An electrophoretic deposition (EPD) method was applied for the preparation of CoFe2O4 (CFO) films on Al2O3/Pt substrates. A coprecipitation process was used to synthesize fine CFO powders with an average particle size of ∼40 nm. Influences of suspension parameters such as solvents, iodine additive, and charged polymer on the suspension stability and film microstructure were investigated in detail. Three suspensions including CFO–acetylacetone, CFO–acetylacetone–0.08 wt% I2 and CFO–acetylacetone–0.2 wt% polyethylenimine (PEI) were optimized, respectively. It was found that CFO was deposited uniformly and the potential required for the deposition was small for the three optimized suspensions. After sintering at 1250 °C for 2 h, the film from CFO–acetylacetone–0.08 wt% I2 showed many cracks, which indicates this suspension is not suitable for preparing high quality CFO ceramic films. While the sintered films fabricated from the other two optimized suspensions exhibited dense structures. Based on the electric and magnetic properties of CFO ceramic films, it can be concluded that CFO–acetylacetone–0.2 wt% PEI is the proper suspension to prepare films with better microstructures and properties.

In order to investigate the phonon scattering mechanisms in double-filled skutterudites, the low-temperature lattice thermal conductivities of In0.1Yb y Co4Sb12 were measured and analyzed based on the Debye model. The eingenmode frequencies of In and Yb were obtained from low-temperature specific heat capacity analysis. It is found that filling these two types of guest atoms with different eingenmode frequencies into the voids in skutterudites could introduce strong point defect and resonant scattering to lattice phonons, thus lead to significant decrease in the lattice thermal conductivity.

An improved smoothness of the Nd-rich/Nd2Fe14B grain interface after annealing is confirmed by detailed microstructure characterization. The crystal structure of the Nd-rich phase adjacent to matrix grain changes from double hexagonal close packed to face-centered cubic (fcc). The fcc-Nd-rich/Nd2Fe14B grain interface approaches coherency with the misfit, ∼4.2% in the present case. This suggests that an atomically smooth and stress-minimized Nd-rich/Nd2Fe14B grain interface reduces the probability of reversed domain nucleation and recovers the coercivity. In addition, oxygen content will play an important role in controlling the interface smoothness.

CdSe nanocrystal sensitized TiO2 nanosheet array heterostructure films were fabricated by a two-step method. Firstly, a single crystalline anatase TiO2 tetragonal nanosheet-array film on a transparent conductive fluorine-doped tin oxide (FTO) substrate was successfully prepared by hydrothermal method. Then, CdSe nanocrystalline sensitizers were deposited on the TiO2 nanosheet array by CBD method. The products were characterized with XRD, SEM, TEM and UV-vis absorption spectroscopy. The effect of the CdSe nanocrystal deposition time and the length of the TiO2 sheet on the photovoltaic performance of the resulting CdSe/TiO2 nanosheet array electrodes were also investigated. In comparison with the non-sensitized TiO2 nanosheet array, the photocurrent of CdSe sensitized TiO2 nanosheet has a great enhancement, which gives some insight to the fundamental mechanism of the performance improvement.

Starting from elemental powder mixtures of FexIn4−xSe3 (x = 0, 0.05, 0.1, 0.15), polycrystalline In4Se3-based compounds with homogeneous microstructures were prepared by mechanical alloying (MA) and hot pressing (HP). With the increase of x from 0 to 0.15, the electrical resistivity and the absolute value of the Seebeck coefficient increased, while the thermal conductivity first decreased and then increased. The maximal dimensionless figure of merit ZT of 0.44 was obtained for the FexIn4−xSe3 (x = 0.05) sample at 723 K.

AgSbTe2compounds have been synthesized via melting and subsequent cooling processes. The effect of cooling process, from air-cooling, water quenching to liquid nitrogen-quenching, on the microstructure and the electrical transport properties of AgSbTe2has been investigated by means of powder X-ray diffraction, electron microscope, electrical resistivity, and Hall coefficient measurements. It has been found that the cooling process has apparent influence on the microstructure and corresponding electrical properties. The phase components and morphology changed as the cooling process altered. The electrical resistivity and the Seebeck coefficient of the as-prepared samples increased from air-cooled to liquid nitrogen-quenched sample.

TiO2 nanotubes array was fabricated by anodization. Effect of reaction duration on the morphology of TiO2 nanotube arrays was studied detailedly. The structure and morphology of the prepared nanotubes array was characterized by X-ray diffraction and scanning electron microscopy, respectively. The fabricated TiO2 arrays were peeled off and adhered to FTO glass with adhesive (mixture of tetrabutyl titanate and polyethylene glycol), then they were sintered at 450 for photoanode of DSSC. The photovoltaic performance of the prepared sample as the DSSC anode was investigated. An open circuit voltage of 0.69V and a short circuit current density of 7.78mA/cm2 were obtained, and the fill factor and the convert efficiency were 0.517 and 2.78%, respectively.

This paper describes the fabrication of CoFe 2 O 4 thick films using the tape casting method from nonaqueous slurry. CoFe 2 O 4 particles with average size of ∼800 nm were prepared by the solid-state reaction method. Sediment volumes and viscosity were tested to study the effects of dispersant in reducing aggregations in slurry. Slurry with 0.25 wt% dispersant amounts and 41.3 wt% solid content showed the optimal stability and rheological properties. A tape velocity of 8 cm/s was used in this study considering the non-Newtonian flow behavior at low shear rate. CoFe 2 O 4 ceramic films sintered at 1150 °C for 2 h have dense structure (relative density of 94%) and exhibited ferromagnetic properties with in-plane saturation magnetization of ∼324 emu/cm 3 .

Ternary oxide Zn 2 SnO 4 was successfully introduced to SnO 2 hierarchical microsphere photoanode for dye-sensitized solar cells by spin-coating method. Zn 2 SnO 4 nanoparticles with average size of 20 nm modified the SnO 2 hierarchical microsphere film uniformly and sufficiently. The shell of Zn 2 SnO 4 nanoparticles plays an important role in resisting acid etchant and suppressing the recombination of conduction band electrons with the oxidized dye. Benefiting from the advantages of both constituents, the composite photoanode exhibits an improved chemical stability and good photoelectric properties in contrast with bare SnO 2 nanostructures.

In this work we have synthesized In0.2+xCo4Sb12+x samples using a melting–annealing–hot pressing procedure, with the In and Sb contents concomitantly varied. The microstructures and thermoelectric properties have been subsequently studied and correlated. Increasing x value leads to an increase of the electrical conductivity, a decrease of the Seebeck coefficient in magnitude, and non-monotonic changes in the power factor and the lattice thermal conductivity. In particular, we have for the first time observed the InSb/Sb eutectic formation through thermal analysis when x is well above 0.2. The high density of interfaces via the formation of InSb/Sb mixture on the grain boundaries seems to decrease the lattice thermal conductivity and accounts for a dimensionless figure of merit, ZT, of 1.0 in In0.8Co4Sb12.6 at 650 K.

Polycrystalline In4Se3−x thermoelectric materials were prepared by a combined process of mechanical alloying and hot pressing (MA-HP), and the effect of Se deficiency on their thermoelectric properties was studied. Starting from elemental In and Se powders, In4Se3 compound was synthesized after mechanical alloying for 1 h. Single-phase In4Se3 compound was obtained in the sample without Se deficiency, while some In impurity was detected in Se-deficient samples. With increasing Se deficiency x, the carrier concentration n increased, and the electrical resistivity and absolute value of Seebeck coefficient of In4Se3−x decreased rapidly. All of the In4Se3−x samples (x > 0) had higher ZT than the stoichiometric In4Se3, with In4Se2.65 showing the highest ZT because of its low thermal conductivity. The maximum ZT reached 0.93 at 700 K.

Starting from elemental powders of Ag, Sn, Pb, Sb, and Te, Sn-substituted single-phase LAST (AgPbmSbTem+2) materials were synthesized by a combined process of mechanical alloying and plasma-activated sintering. The effect of Sn content on thermoelectric (TE) properties of the Sn-substituted LAST materials was investigated in detail. With increase of Sn/Pb ratio, the fraction of SnTe in the (Pb,Sn)Te-based solid solution increased, and the lattice spacing decreased accordingly. The electrical conductivity, thermal conductivity, and power factor also increased with increasing substitutional Sn content. It was found that the composition AgPb9Sn9SbTe20 had superior TE properties compared with other compositions, and the maximum ZT of 0.70 was achieved at 675 K for this composition.

Oriented thermoelectric (TE) p -Sb 2 Te 3 and n -Bi 2 Te 3 thin films with special nanostructures have been synthesized by a simple vacuum thermal evaporation technique. The composition and microstructure of the films were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM), presenting a well preferential crystal growth with dense slender columnar grains grown perpendicular to the substrate, and energy dispersive X-ray spectrum (EDX) indicating the compositions distribution in the films. The electric transport properties, i.e., conductivity and Seebeck coefficient, and the thermal transportation of the oriented films show optimized properties. Prototype devices were built up by p and n elements in series and parallel circuits. The largest output power and cooling could be achieved in Sb 2 Te 3 parallel device with P max = 6.51 μW at Δ T = 106 K, and cooling of 4.1 K at 2 V. The 24-pair p – n couples series device could output maximum voltage of 313 mV at Δ T = 102 K. The power generation and the cooling of the devices show times enhanced TE performances than those consisting of common films. The results proved that introducing nanostructures into films is an effective choice to obtain high-efficient micro TE device.

Bi2Te3 nanopowders with an average grain size of about 40 nm were synthesized by vacuum arc plasma evaporation. The n-type bulk Bi2Te3 nanocomposites were prepared by consolidating the mixtures of these nanopowders and mechanically alloyed powders using plasma activated sintering, and the effect of the addition of nanopowders on the thermoelectric properties of bulk Bi2Te3 nanocomposites was investigated. With increasing the content of the added nanopowders, the electrical resistivity and Seebeck coefficient of the nanocomposites increased and the thermal conductivity decreased. When the content of the added nanopowders was 20 wt%, the thermal conductivity decreased by 21.4% compared with that of the nanopowders-free compounds. A preliminary investigation showed that the addition of nanopowders was an effective way to decrease the thermal conductivity and increase the thermoelectric efficiency.

In order to pursue high catalytic performance of Ni-Al intermetallic compounds for hydrogen production, we synthesized Ni-Al intermetallic nanoparticles from Ni-Al alloy ingots by vacuum arc plasma evaporation technique for the first time. The characterization of the synthesized nanoparticles was carried out using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy. The catalytic properties of the Ni-Al nanoparticles for methanol decomposition were evaluated. It is found that the nanoparticles had a large surface area above 70 m2/g, and showed very high catalytic activity for methanol decomposition.

Superhard TiB2 thin films were deposited on steel substrates using the radio-frequency magnetron-sputtering technique with a low normalized substrate temperature (0.1

This paper concerns the electrochemical atom-by-atom growth of VA-VIA compound semiconductor thin film superlattice structures using electrochemical atomic layer epitaxy. The combination of the Bi2Te3 and Sb2Te3 programs and Bi2Te3/Sb2Te3 thin film superlattice with 18 periods, where each period involved 21 cycles of Bi2Te3 followed by 21 cycles of Sb2Te3, is reported here. According to the angular distance between the satellite and the Bragg peak, a period of 23 nm for the superlattice was indicated from the X-ray diffraction (XRD) spectrum. An overall composition of Bi 0.25Sb0.16Te0.58, suggesting the 2:3 stoichiometric ratio of total content of Bi and Sb to Te, as expected for the format of the Bi2Te3/Sb2Te3 compound, was further verified by energy dispersive X-ray quantitative analysis. Both field-emission scanning electron microscopy and XRD data indicated the deposit grows by a complex mechanism involving some 3D nucleation and growth in parallel with underpotential deposition. The optical band gap of the deposited superlattice film was determined as 0.15 eV by Fourier transform infrared spectroscopy and depicts an allowed direct type of transition. Raman spectrum observation with annealed and unannealed superlattice sample showed that the LIF mode has presented, suggesting a perfect AB/CB bonding in the superlattice interface.

Bi2Te3 plate-like crystals with homogeneous hexagonal morphology were rapidly synthesized using a microwave assisted wet chemical method in 30 min. These Bi2Te3 nanoplates possessed a fixed edge with a length of ~0.5–2 µm, and the thickness was less than ~100 nm. The n-type Bi2Te3 nanocomposites were prepared by consolidating mixtures of these nanoplates and mechanically alloyed powders using plasma activated sintering, and the effect of nanoplate addition on the thermoelectric properties of the nanocomposites was investigated. When the content of the doped nanoplates was 15 wt%, the lattice thermal conductivity of the Bi2Te3 nanocomposites decreased by 18% compared with that of the undoped compounds. A preliminary investigation showed that nanopowder addition was an effective way to decrease the thermal conductivity and increase the thermoelectric efficiency.

Ag-doped Bi2(Te0.95Se0.05)3 thermoelectric thin films (Ag: 0?0.5?wt%) with thickness of 800?nm have been deposited on glass substrates by the flash evaporation method at 473?K. The structure and morphology of the thin films were analysed by x-ray diffraction and field emission scanning electron microscopy, respectively. The effects of Ag doping concentration on the thermoelectric properties of the annealed thin films were investigated by room-temperature measurement of the Seebeck coefficient and electrical resistivity. The thermoelectric power factor was enhanced to 16.1??W?cm?1?K?2 at 0.2?wt% Ag doping. The Seebeck coefficients are positive with increasing Ag doping concentration from 0.25 to 0.5?wt%. And the thin films show p-type conduction.

Starting from elemental bismuth, tellurium and selenium powders, n-type Bi2Te2.85Se0.15 solid solution with a fine microstructure was prepared by mechanical alloying and equal channel angular extrusion (ECAE) in the present work. The effect of extrusion temperature on the microstructure and thermoelectric properties of the as-ECAEed samples was investigated. A preferentially oriented microstructure with the basal planes (0 0 l) in the parallel direction to extrusion was formed, and the orientation factors F of the (0 0 l) planes of the 703 K and 753 K ECAEed Bi2Te2.85Se0.15 alloys were 0.26 and 0.28, respectively. The electrical resistivity and the Seebeck coefficient decreased, and the thermal conductivity increased with increasing extrusion temperature. The electrical and thermal transmission performances were strongly affected by the preferentially oriented microstructure and the preferential orientation improved the thermoelectric properties of the ECAEed Bi2Te2.85Se0.15 alloys in the parallel direction to extrusion. The maximum dimensionless figure of merit was obtained when extruded at 753 K at a testing temperature of 343 K, ZT = 0.66.

In this paper, Pd 60 Cu 40 / V – 15 Ni composite membranes were prepared by DC co-sputtering method, and the effect of the Pd 60 Cu 40 overlayer thickness on hydrogen permeability of the Pd 60 Cu 40 / V – 15 Ni composite membrane was studied in the temperature range of 423–673 K. The depositing rate for the overlayer was about 3.5 nm s - 1 when the sputtering voltage of the Cu target and Pd target were set at 395 and 340 V, respectively, four composite membranes with different overlayer thicknesses that corresponded to deposition durations of 30, 60, 90 and 120 s, respectively, were measured under pure hydrogen atmosphere. The composite membrane with the overlayer thickness corresponding to the 60 s deposition duration, showed the highest hydrogen permeability compared to those with the other thicknesses, and its maximum hydrogen permeability of 3.72 × 10 - 8 molH 2 m - 1 s - 1 Pa - 1 / 2 was obtained at 573 K. Hydrogen permeation kinetics of the composite membranes was mainly limited by bulk diffusion at temperature higher than 473 K. When the temperature was lower than 473 K, the hydrogen permeation flux saturated at high upstream H 2 pressures, surface-related reaction should be responsible for the flux saturation at low temperature.