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The lattice vibrations and optical properties of α-Ga2O3 are investigated by polarized Raman scattering and spectroscopic ellipsometry measurements at room temperature. Three types of epitaxial α-Ga2O3 film samples were grown on c-plane sapphire substrates by halide vapor phase epitaxy (HVPE) in three different growth modes, namely by O2-control, Ga-control, and reference mode. Seven Raman active phonons and three infrared active phonons are determined experimentally for all samples. The relative intensities of Eg(2), Eg(4), and Eg(5) modes in Raman spectra varies as a function of growth mode. The growth mode has no obvious effect on the infrared active Eu(2) and Eu(4) modes, while phonon lifetime of the Eu(3) mode drastically changes. For the Eu(3) mode, the O2-control sample exhibits a significantly reduced broadening factor of 7.6 cm−1 compared with that of the reference (10 cm−1), and the Ga-control (16.6 cm−1) samples. All the three types of samples show similar complex ordinary dielectric functions in the spectral range between 0.5 and 6.5 eV indicating no obvious changes within the band structure by changing the growth mode. [ABSTRACT FROM AUTHOR]

The electric forces are the main factor responsible for the characteristic jet path and stretching in electrospinning. The distribution of the electric field determines the quality of the electrospinning. In this paper, a glass flywheel nozzle is designed, and a ring electrode and a capacitor are added between the nozzle and the receiving plate. Theoretical calculations prove the feasibility of the design. The finite element analysis software COMSOL Multiphysics5.0 is used for electric field simulation. The effect of the voltage across the ring electrode and capacitor on the electric field was studied. It is found that when the ring electrode is connected to 10 kV voltage and the voltage across the capacitor is 5 kV, the uniformity of the electric field is significantly improved, which provides a reference for the future optimization of the electrostatic spinning electric field. [ABSTRACT FROM AUTHOR]

A modified model is proposed to describe the dielectric nonlinear behavior in bismuth-based cubic pyrochlores by introducing non-tunable factor into Tagantsev's model. To validate the model, Bi1.5MgNb1.5-x Ti x O7 (BMNT) films were fabricated via chemical solution deposition. Bias field dependence of the permittivity predicted by the modified model agrees well with experimental results. A method for calculating barrier heights for hopping ions is presented based on the modified model. The maximum barrier heights for hopping dipoles in BMNT films derived from the model decrease from 0.206eV to 0.172eV with increasing Ti content from x=0 to x=0.15. [ABSTRACT FROM AUTHOR]

Abstract: Cubic pyrochlore Bi3/2ZnNb3/2O7, Bi3/2Zn1/2Mg1/2Nb3/2O7 and Bi3/2Zn1/3Mg1/3Ni1/3Nb3/2O7 thin films were fabricated on Au/Ti/SiO2/Si (100) substrates using a chemical solution spin coating process. Tunability of Bi3/2ZnNb3/2O7 thin films was improved from 22% to 35% by substituting Mg2+ and Ni2+ for Zn2+ at a bias field of ∼1MV/cm. Dielectric loss of thin films remained below 0.004 at 1MHz and was almost independent of Mg2+ and Ni2+ doping and bias field. Effects of Mg2+ and Ni2+ substitution on the tunability were discussed based on Raman spectral analyses. The F 2g(1) mode correlated with the vibration of A–O bond significantly influenced the tunability of thin films. [Copyright &y& Elsevier]

As a typical representative of Ga-based III-V compound semiconductor material, the pressure-induced structural phase transition of gallium phosphide (GaP) has received more attention, while the present work explains the electronic structure and photoconductivity properties under high pressure, especially. The paper focuses on the high-pressure electronic structure and photoconductivity properties up to 50.0 GPa in GaP, along with the ZB (zinc-blende structure) to RS (rock salt structure) phase structural transition using enthalpy calculation. The discontinuous thermal expansion coefficient and unit cell volume collapse by 15.0–15.5% are observed at around 39.2 GPa due to reversible structural phase transition under compression and decompression conditions, which is also reflected in the measured discontinuous Hall coefficient and conductivity at approximately 39.0 GPa. The computed semiconductor-to-metal transition is determined to occur at 24.5 GPa by band-gap closure in good agreement with the experimentally determined transition pressure. The light illumination provides a potential way to reduce conductivity without effect on pressure of phase transition. [ABSTRACT FROM AUTHOR]

Bi2Te3 is a thermoelectric material with high thermoelectric conversion efficiency near room temperature. The control of its components is an effective method to improve the thermoelectric properties of Bi–Te based materials. In this paper, seven-layer Bi–Te thin films with Te content ranging from 36.29% to 77.29% were deposited on non-rotating glass substrates by co-sputtering and the samples were rapidly thermally annealed in a nitrogen atmosphere. The films were characterized by x-ray diffraction, scanning electron microscopy, and Hall effect measurement methods, and the effects of the components on the film morphology and thermoelectric properties were investigated. The results showed that the films were composed of mainly Bi2Te3 after annealing. As the Te element content increased, the grain size in the film surface first increased and then decreased, the layers between the interfaces became less obvious, and the number of voids decreased. Subsequently, thin films with Te content between 60% and 75% were deposited on a rotating substrate; the thermoelectric properties were relatively high and stable after annealing. A film with Te content of 69.29% had a good crystallization quality and large grain size with a maximum power factor of 8.17 µW/(K2 cm) after annealing at 350 °C for 17 min. [ABSTRACT FROM AUTHOR]

The electrical transport properties of As 2 Te 3 were studied under high pressure using theoretical and experimental methods. The structural phase transition was observed at around 25 GPa using first-principles calculations, which was reflected in the collapse of the cell volume and the calculation of the enthalpy. The pressure-induced metallization was confirmed at approximately 7 GPa from closed energy bands and density of states, and the resistivity of variable temperature also shown a piece of evidence for metallization at 7.1 GPa. The curves of the electrical parameters at 7 GPa are consistent with the theoretical calculations. In addition, discontinuous changes in carrier parameters were observed at around 15 GPa, which is attributed to the isostructural phase transition of As 2 Te 3. Studying the electrical transport properties of As 2 Te 3 under high pressure, especially its pressure-induced metallization properties, can provide a theoretical basis for its application in storage devices and thermoelectric materials, and help to understand the properties of other A 2 B 3 -type compounds under high pressure. [Display omitted] [ABSTRACT FROM AUTHOR]

The electrical transport properties of gallium phosphide (GaP) under high pressure (up to 50 GPa) are investigated using in situ impedance‐spectrum and Hall‐effect measurements. A discontinuous resistance is observed at 9.9 GPa because of the pressure‐induced grain boundary effect, whereas the pressure‐induced metallization of GaP occurred at ≈24.6 GPa. The metallization transition is determined by measuring the temperature‐dependent resistance and resistivity, and the transition is observed to be reversible. The main cause of the sharp decrease in the resistance and resistivity is a pressure‐induced structural phase transition at 39.3 GPa, as reflected by the measured Hall parameters. [ABSTRACT FROM AUTHOR]

The investigation of the electrical transport properties of ZrS 2 is conducted up to 30.7 GPa using first-principles calculation and electrical experimental methods. The electrical parameters of ZrS 2 are investigated under high pressure conditions using the thin film integrated microcircuit technology on a diamond anvil cell. The structural phase transitions occur at approximately 2.0 GPa and 6.0 GPa, as evidenced by changes in the energy band structure and discontinuities in electrical parameters. At around 12.3 GPa, the pressure-induced metallization is observed by temperature-induced resistivity and the closing of the band gap. The sudden decrease in resistivity can be attributed to the combined contribution of an increase in carrier concentration and mobility. Similarly, the abrupt decrease in Hall coefficient is attributed to the increase in carrier concentration. [Display omitted] • ZrS 2 undergoes two phase transitions by theoretical calculation. • The reversible structural phase transitions causes changes in electronic properties. • Metallization occurs at around 12.3 GPa via temperature-induced resistivity. • The measured electrical parameters confirm the generation of phase transitions. [ABSTRACT FROM AUTHOR]

The thermoelectric cooler (TEC) is a kind of cooling equipment which used to dissipate heat from the devices by Peltier effect. The cooling capacity (Qc) and coefficient of performance (COP) are both significant performance parameters of a thermoelectric cooler. In this article, three-dimensional numerical simulations are carried out by finite element analysis based on the temperature-dependent materials properties. The experimental and geometrical parameters have important effects on the TEC performance which have been analysed, such as electrical current, geometric configuration of thermoelectric leg, Thomson effect, thermal contact resistances and electrical contact resistances. The results show when the Thomson effect is ignored, the maximum difference in the cooling capacity is 7.638 W while the maximum difference in the COP is 0.09. When contact effect is not considered, the maximum difference in the cooling capacity is 22.06 W while the maximum difference in the COP is 0.75. Furthermore, the cooling capacity and COP have also been simultaneously optimized according to the multi-objective genetic algorithm. The best optimal value is obtained making use of TOPSIS (technique for order preference by similarity to an ideal solution) method from Pareto frontier. Investigated on these optimal design parameters which were anticipated to provide real guidance in industry. [ABSTRACT FROM AUTHOR]

The electrical transport properties of indium trisulfide (In2S3) under high pressure were investigated using the in situ Hall-effect and temperature dependent resistivity measurements. Resistivity, Hall coefficient, carrier concentration, and mobility were obtained at pressures up to 41.6 GPa. Pressure induced metallization of In2S3 occurred at approximately 6.8 GPa. This was determined by measuring temperature dependent resistivity. The metallization transition was also determined from compression electrical parameters, and the decompression electrical parameters indicated that the metallization was a reversible transition. The main cause of the sharp decline in resistivity was the increase in carrier concentration at 6.8 GPa. Superconductivity was not observed at the pressures (up to 32.5 GPa) and temperatures (100–300 K) used in the experiment. [ABSTRACT FROM AUTHOR]

The high-pressure electronic structure and electrical properties of Mg 2 Pb are investigated from ambient pressure to 42 GPa by first-principles calculation. Mg 2 Pb undergoes reversible structural transitions from F m 3 ‾ m structure to Pnma structure and then to P6 3 /mmc structure. The structural phase transitions are determined respectively at around 6 GPa and 28 GPa using pressure-dependent enthalpy calculations, which are also reflected from the cell volume collapse and discontinuous axial ratios of lattice constants. The sliding of Mg and Pb atomic layers is revealed via the Mg 1 –Pb–Mg 2 atom pair during structural phase transitions, corresponding to abrupt decrease of c/b and a/b. The semimetal-to-metal transition is also observed at approximately 28 GPa owing to energy-band closure, whilst metallic character is strengthened with increasing pressure. The paper is prone to theoretically explore the structural phase transition and metallization of Mg 2 Pb-type family under extreme conditions. [Display omitted] • The reversible twice structural phase transitions are observed for Mg2Pb. • The structural phase transitions are found at around 6 GPa and 28 GPa for Mg2Pb. • The semimetal-to-metal transition transition is determined at approximately 28 GPa. • The sliding of Mg and Pb atomic layers is revealed via the Mg1-Pb-Mg2 atom pair. • The extreme high-pressure behavior of Mg2X-type (X=carbon group) family is disclosed. [ABSTRACT FROM AUTHOR]

As an electroluminescentdevice, the coupling relationship between light-emitting diode (LED) input currents, optical power, and LED junction temperature is a complicated multiphysics process. In this paper, a simplified LED photoelectron-thermal (PET) model by artificial neural network (ANN), which can translatemultiphysics field issue into a singlephysics field problem, ismentioned to study the coupling relationship. In the first, an LED lumens, optical power, and electric power at different temperatures are monitored in a temperature controlling integrating sphere. Then, a backpropagation (BP) ANN is trained by these data to construct an LED Photo-Electron-Thermal (PET) relationship. In addition, LED luminaire thermal analyzing is performed using a finite-element method on the outputs of the BP ANN. Finally, the advantage of this method in terms of saving computing resources and computing time is analyzed by comparing the degrees of freedom in different models. The result shows that at least 6.7 times computing resource are saved by this method, which will reduce the LED thermal management system analyzing time greatly. Finally, the application and extension of this model are discussed. [ABSTRACT FROM PUBLISHER]

The structural and electronic properties of WTe 2 are studied from ambient pressure to 30.0 ​GPa. The pressure-induced structural phase transition is found from T d phase to 1T′ phase above 10.0 ​GPa by lattice offset, which is also reflected at approximately 11.2 ​GPa based on the discontinuous electrical parameters. A pair of hole wave and electron wave packets of T d phase gradually overlap revealing the reversible T d -to-1T′ phase structural transition. WTe 2 is observed to undergo semimetal-to-semiconductor transition owing to the calculated energy band up to 15 ​GPa, which is also observed at 11.2 ​GPa according to the resistivity-temperature curves under compression and decompression conditions. The electronic density of states at the Fermi level is mainly contributed by the d orbital of W and the p and s orbital of Te. The photoconductivity property is shown by the theoretical and experimental methods. [Display omitted] • The structural transition of WTe 2 is shown from T d phase to 1T′ phase above 10.0 ​GPa by lattice-offset. • The pressure-induced semimetal-to-semiconductor transition is obtained caused by Td-to-1T′ structural phase transition. • A pair of hole and electron wave packets of T d -WTe 2 gradually overlap and finally disappear due to lattice-offset. • The photoconductivity property of WTe 2 is observed and the phase transition pressure can be reduced by photoconductivity. [ABSTRACT FROM AUTHOR]

[Display omitted] • The dual differential coil pair magnetic module (DDP module) and the multiple differential coil pair magnetic module (MDP module) are designed. • A multi-channel magnetic detection method for metal foreign bodies is defined based on DDP/MDP module. • The detection accuracy of 3.0% and the initial detection value of 3.5 V can be achieved by the multi-channel detection method based on double/multiple differential coil pair magnetic module. The DDP/MDP (Dual Differential coil Pair/ Multiple Differential coil Pair) module are designed, and a multi-channel detection method for metal foreign bodies is defined based on DDP/MDP module. The DDP/MDP module structure is optimized and designed by loose mathematical modeling and multi-physics electromagnetic simulation according to the B X/Y/Z. A multi-channel detection platform is built based on the 16-bit MDP module composed of 4-bit UQV-DDP modules. Given the standard metal foreign body detection test, the system reaches the optimal metal foreign body detection state, in which the detection area is reduced by 3/4, and the parameter uncertainty is reduced to 0.5%-1.5%, responding to overall the module width range of 60–100 mm, the radius of 150 mm, and the diagonal distance of 200 mm, respectively. By comparative analysis, the accuracy of the multi-channel detection method is 3.0%, and the initial detection value is 5.0 V based on the MDP module. In comparison, the detection accuracy of the multi-channel detection method is 5.0%, and the initial detection value is 3.5 V based on the DDP module. Taking use of 16-bit MDP/DDP module detection platform, the detection accuracy of 3.0% and the initial detection value of 3.5 V can be achieved by the multi-channel detection method based on DDP/MDP module. [ABSTRACT FROM AUTHOR]

Abstract: The Bi1.5MgNb1.5O7 (BMN) thin films were prepared on Au-coated Si substrates by rf magnetron sputtering. We systematically investigated the structure, dielectric properties and voltage tunable property of the films with different annealing temperatures. The relationships of leakage current and breakdown bias field with annealing temperature were firstly studied and a possible explanation was proposed. The deposited BMN thin films had a cubic pyrochlore phase when annealed at 550°C or higher. With the increasing of annealing temperature, the dielectric constant and tunability also went up. BMN thin films annealed at 750°C exhibited moderate dielectric constant of 106 and low dielectric loss of 0.003–0.007 between 10kHz and 10MHz. The maximum tunability of 50% was achieved at a bias field of 2MV/cm. However, thin films annealed at 750°C had lower breakdown bias field and higher leakage current density than films annealed below 750°C. The excellent physical and electrical properties make BMN thin films promising for potential tunable capacitor applications. [Copyright &y& Elsevier]

In this study, a full-scale three-dimensional trapezoidal thermoelectric cooler model is constructed to study its cooling performance and mechanical reliability using finite element simulation. Temperature dependent material properties are considered in this work. The boundary conditions similar to those in a real experimental environment are applied. The effects of the input electrical current and geometry of the thermoelectric leg on the cooling performance and reliability of a trapezoidal thermoelectric cooler are analyzed, and a comparison is made with a rectangular thermoelectric cooler. The results indicate that increasing the leg height and the variable cross-sectional design of the leg can improve the cooling performance of the trapezoidal thermoelectric cooler. Compared to the original rectangular thermoelectric cooler, the minimum chip temperature was reduced by 0.87% under the trapezoidal thermoelectric cooler with optimized geometry. Furthermore, increasing the leg height enhances the mechanical reliability of the trapezoidal thermoelectric cooler, while the trapezoidal design of the leg reduces its mechanical reliability. The maximum von Mises stress of the leg for the trapezoidal thermoelectric cooler with optimal cooling performance increased by 40.1%. The results of this work provide useful guidance for the structural design of trapezoidal thermoelectric coolers. [ABSTRACT FROM AUTHOR]

In this study, a full-scale three-dimensional trapezoidal thermoelectric cooler model is constructed to study its cooling performance and mechanical reliability using finite element simulation. Temperature dependent material properties are considered in this work. The boundary conditions similar to those in a real experimental environment are applied. The effects of the input electrical current and geometry of the thermoelectric leg on the cooling performance and reliability of a trapezoidal thermoelectric cooler are analyzed, and a comparison is made with a rectangular thermoelectric cooler. The results indicate that increasing the leg height and the variable cross-sectional design of the leg can improve the cooling performance of the trapezoidal thermoelectric cooler. Compared to the original rectangular thermoelectric cooler, the minimum chip temperature was reduced by 0.87% under the trapezoidal thermoelectric cooler with optimized geometry. Furthermore, increasing the leg height enhances the mechanical reliability of the trapezoidal thermoelectric cooler, while the trapezoidal design of the leg reduces its mechanical reliability. The maximum von Mises stress of the leg for the trapezoidal thermoelectric cooler with optimal cooling performance increased by 40.1%. The results of this work provide useful guidance for the structural design of trapezoidal thermoelectric coolers. [ABSTRACT FROM AUTHOR]