Ultrahigh thermoelectric properties of p‐type Bi_(x)Sb_(2−x)Te_(3) thin films with exceptional flexibility for wearable energy harvesting

Use of a flexible thermoelectric source is a feasible approach to realizing selfpowered wearable electronics and the Internet of Things.Inorganic thin films are promising candidates for fabricating flexible power supply,but obtaining highthermoelectric‐performance thin films remains a big challenge.In the present work,a p‐type Bi_(x)Sb_(2−x)Te_(3) thin film is designed with a high figure of merit of 1.11 at 393 K and exceptional flexibility(less than 5%increase in resistance after 1000 cycles of bending at a radius of∼5 mm).The favorable comprehensive performance of the Bi_(x)Sb_(2−x)Te_(3) flexible thin film is due to its excellent crystallinity,optimized carrier concentration,and low elastic modulus,which have been verified by experiments and theoretical calculations.Further,a flexible device is fabricated using the prepared p‐type Bi_(x)Sb_(2−x)Te_(3) and n‐type Ag_(2)Se thin films.Consequently,an outstanding power density of∼1028μWcm^(−2)is achieved at a temperature difference of 25 K.This work extends a novel concept to the fabrication of highperformance flexible thin films and devices for wearable energy harvesting.

Influence of the substitution of Sm, Gd, and Dy for La in La_(0.7)Sr_(0.3)MnO_3 on its magnetic and electric properties and strengthening effect on room-temperature CMR

A series of La0.7-xSmxSr0.3MnO3, La0.7-xGdxSr0.3MnO3, and La0.7-xDyxSr0.3MnO3 （x=0.00, 0.10, 0.20, 0.30） samples were prepared by the solid-state reaction method. The influence of the substitution of Sm, Gd, and Dy for La on the magnetic and electric properties and on the magnetoresistance （MR） was studied through measurements of M-T curves and p-T curves. The results showed that： lattice distortion induced by substitution of Sm, Gd, and Dy for La and extra magnetism of substitution had great influence on the magnetic and electric properties of pcrovskite manganites; substitution of magnetic rare earth element for La was an effective way to change Curie temperature and to strengthen MR in perovskite manganites; and appropriate substitution proportion would generate large MR near room temperature.

Gaseous Penetration of Pr into PbTiO_3 Ceramics and Their Electric Properties

The gaseous Pr-penetration is a new method to modify ceramics, which is expected to be a promising method for producing new conductor ceramic materials. The gaseous penetration of Pr into PbTiO_3 ceramics and their improved electric properties were reported. Through XRD, EPMA and SEM analysis,it is confirmed that the gaseous penetration makes Pr enter into PbTiO_3 ceramics, and the new compound of Pr_2Ti_2O_7 is formed by the penetration of Pr in the gaseous state. The formed new Pr_2Ti_2O_7-PbTiO_3 ceramic materials have a significant change in electric properties. The room temperature resistivity decreases from 2.0×10^(10) Ω·m to 9.487 Ω·m. The grain resistance and the grain boundary resistance decrease with increase in temperature, and the PTCR effect disappears. The tendency of transition to a conductive body is manifest.

First Principle Study on the Magnetic and Electric Properties of Wurtzite Cr-phosphides and Cr-sulphides： Several Half-metallic Ferromagnets

The geometrical structures of wurtzite CrX （X=As, Sb, O, Se, and Te） were optimized, then their electric and magnetic properties were investigated by the first-principle calculations within the generalized gradient approximation for the exchange-correlation functional based on the density functional theory. These Cr-phosphides and Cr-sulphides were predicted to be half-metallic ferromagnets whose spin-polarization at the Fermi level is absolutely 100%. The molecular magnetic moments of Cr-phosphides and Cr-sulphides are 3.00 and 4.00 μB, which arise mainly from Cr-ions, respectively. There is ferromagnetic coupling in both Cr- phosphides and Cr-sulphides. The Curie temperatures of Cr-sulphides and Cr-phosphides are high. The electronic structures of Cr-ions are a1g^2↑↓t1u^4↑↓t1u^1↑↓eg^2↑↓in Cr-phosphides and a1g^2↑↓t1u^4↑↓t1u^1↑t2g^3↑in Cr-sulphides, respectively.

Influence of the gassing materials on the dielectric properties of air

Influence of the gassing materials, such as PA6, PMMA, and POM on the dielectric properties of air are investigated. In this work, the fundamental electron collision cross section data were carefully selected and validated. Then the species compositions of the air–organic vapor mixtures were calculated based on the Gibbs free energy minimization. Finally, the Townsend ionization coefficient, the Townsend electron attachment coefficient and the critical reduced electric field strength were derived from the calculated electron energy distribution function by solving the Boltzmann transport equation. The calculation results indicated that H;O with large attachment cross sections has a great impact on the critical reduced electric field strength of the air–organic vapor mixtures. On the other hand, the vaporization of gassing materials can help to increase the dielectric properties of air circuit breakers to some degree.

Microstructure and Electric Properties of Dy and Sm-Doped Bismuth Titanate Ceramics

The effect of Dy and Sm doping on microstructure and electric properties of bismuth titanate ceramics were investigated by means of XRD, SEM and AFM. The results showed that the grain growth habit was anisotropy of BIT ceramics doped with Dy, Sm at a concentration range of 0.5%～2.5%. However, c-axis decreased more obviously with increasing dopant concentration of Sm-doped sample than Dy-doped sample. As a result, the shape of grains of Sm-doped sample were granular, in contrast with Dy-doped sample with template particles. The grain size of Sm-doped sample decreased significantly, which led to a large dielectric constant and remanent polarization.

Effects of O_2 Plasma Treatment on the Chemical and Electric Properties of Low-k SiOF Films

With the progress of ULSI technology, materials with low dielectric constant are required to replace SiO2 film as the interlayer to scale down the interconnection delay. Fluorinated Si oxide thin films (SiOF) are a promising material for the low dielectric constant and the process compatibility in existing technology. However, SiOF films are liable to absorb moisture when exposed to air. By treating the SiOF films with O-2 plasma, it was found that the moisture resistibility of SiOF films was remarkably improved. The mechanism of the improvement in stability of dielectric constant was investigated. The results show that: 1) F atoms dissociated from the films and the bond angle of Si-O-Si decreased. 2) The plasma treatment enhanced the strength of Si-F bonds by removing unstable =SiF2 structures in the films. Resistibility of SiOF films in moisture was improved.

Influence of Excessive SiO_2 or TiO_2 on the Electric Properties of Ba_(0.92)Ca_(0.08)TiO_3 PTCR Ceramics

The dependence of electrical properties of Ba0.92Ca0.08TiO3 PTC ceramics on the SYO2 or TiO2 content was studied. The dependence of room, temperature resistivity on the SiO2 content was determined by the variation of the microstructure of Ba0.92Ca0.08TiO3 PTC ceramics . It was shown that a small amount of excessive TiO2 (2mol% ) added could increase the dielectric constant of materials, and it results in a reducing of the potential height (e·) of grain boundary. Thus, samples with particularly low room temperature resistivity were obtained. The relationship of PTC effect with the TiO2 content was also discussed by using the chemistry defect theory . The inferior PTC effect caused by excessive TiO2 may be concerned with the behavior of oxygen vacancies in the grains of ceramics.

Effects of heavy metal on dielectric properties of E. coli revealed by dielectric spectroscopy

Dielectric spectroscopy of E. coli cell before and after exposure to heavy metals Cd^2＋ , Cu^2＋ , Zn^2＋ and Ca^2＋ was investigated. The results indicate that changes in dielectric spectra reflect effects of heavy metal on the structure and function of E. coli cells. Heavy metal can change membrane capacitance as well as pennittivity and conductivity of the cytoplasm. Changes in volume fraction suggested that dielectric measurement could monitor the growth of E. coli cells. These results demonstrated that dielectric spectroscopy was a potential effective technique for studying electric properties of biological cells.

Frequency and voltage-dependent electrical and dielectric properties of Al/Co-doped PVA/p-Si structures at room temperature

In order to investigate of cobalt-doped interracial polyvinyl alcohol （PVA） layer and interface trap （Dit） effects, A1/p- Si Schottky barrier diodes （SBDs） are fabricated, and their electrical and dielectric properties are investigated at room temperature. The forward and reverse admittance measurements are carded out in the frequency and voltage ranges of 30 kHz-300 kHz and -5 V-6 V, respectively. C-V or er-V plots exhibit two distinct peaks corresponding to inversion and accumulation regions. The first peak is attributed to the existence of Dit, the other to the series resistance （Rs）, and interfacial layer. Both the real and imaginary parts of dielectric constant （er and err） and electric modulus （Mr and Mrr）, loss tangent （tan~）, and AC electrical conductivity （aac） are investigated, each as a function of frequency and applied bias voltage. Each of the M~ versus V and Mrr versus V plots shows a peak and the magnitude of peak increases with the increasing of frequency. Especially due to the Dit and interfacial PVA layer, both capacitance （C） and conductance （G/w） values are strongly affected, which consequently contributes to deviation from both the electrical and dielectric properties of A1/Co-doped PVA/p-Si （MPS） type SBD. In addition, the voltage-dependent profile of Dit is obtained from the low-high frequency capacitance （CLF-CHF） method.

Electrical and dielectric properties of Al/p-Si and Al/perylene/p-Si type diodes in a wide frequency range

The perylene （C20H12） layer effect on the electrical and dielectric properties of Al/p-Si （MS） and Al/perylene/p-Si （MPS） diodes have been investigated and compared in the frequency range of 0.7 kHz-2 MHz. Experimental results show that C-V characteristics give an anomalous peak for two structures at low frequencies due to interface states （Nss） and series resistance （Rs）. The increases in C and G/o3 at low frequencies confirm that the charges at interface can easily follow an ac signal and yield excess capacitance and conductance. The frequency-dependent dielectric constant （er） and dielectric loss （e＇） are subtracted using C and G/co data at 1.5 V. The eI and e＂ values are found to be strongly dependent on frequency and voltage, and their large values at low frequencies can be attributed to the excess polarization coming from charges at traps. Plots of ln（o＇ac）-ln（w） for two structures have two linear regions, with slopes of 0.369 and 1.166 for MS, and of 0.077 and 1.061 for MPS, respectively. From the C 2-V characteristics, the doping acceptor atom concentration （NA） and barrier height （,~） for Schottky barrier diodes （SBDs） 1.303 ~ 1015 cm-3, and 1.10 and I. 13 eV, respectively. of MS and MPS types are also obtained to be 1.484 ~ 1015

Sol-gel auto-combustion synthesis of K_xNa_(1-x)NbO_3 nanopowders and ceramics: Dielectric and piezoelectric properties

The KxNa1-xNbO3 nanopowders with cubic-like morphology and an average size of about 50 nm were synthesized by sol-gel auto-combustion method.And then,the ceramics were prepared and the phase transition,microstructure and electrical properties of the KxNa1-xNbO3 ceramics were investigated.Pure perovskite phases of the KxNa1-xNbO3 ceramics were confirmed by XRD patterns and the K0.50Na0.50NbO3 ceramics show the coexistence of orthorhombic and monoclinic structures.SEM micrographs show that all samples have bimodal grain size distributions and the number of the small grains decrease with increasing K+content in the bimodal grain size distribution system.The K0.50Na0.50NbO3 ceramics with the uniform grain size and the maximum density show excellent electrical properties withεr=467.40,tanδ=0.020,d33=128 pC/N and kp=0.32 at the room temperature,demonstrating that the properties of the K0.50Na0.50NbO3 powers prepared by sol-gel auto-combustion are excellent and the ceramics are promising lead-free piezoelectric materials.

Improvement of sintering,nonlinear electrical,and dielectric properties of ZnO-based varistors doped with TiO2

The effects of TiO2 on sintering and nonlinear electrical properties of（98.5-x）ZnO–0.5MnO2–0.5Co2O3-0.5Bi2O3–xTiO2（x = 0.3,0.5,0.7,0.9 mol%） ceramic varistors prepared by the ceramic technique are investigated in this work.The optimum sintering temperature of the prepared samples is deduced by determining the firing shrinkage and water absorption percentages.The optimum sintering temperature is found to be 1200℃,at which each of the samples shows a maximum firing shrinkage and minimum water absorption.Also minimum water absorption appears in a sample of x = 0.9 mol%.Higher sintering temperature and longer sintering time give rise to a reduction in bulk density due to the increased amount of porosity between the large grains of ZnO resulting from the rapid grain growth induced by the liquid phase sintering.The crystal size of ZnO decreases with increasing TiO2 doping.The addition of TiO2 improves the nonlinear coefficient and attains its maximum value at x = 0.7 mol% of TiO2,further addition negatively affects it.A decrease in capacitance consequently in the dielectric constant is recorded with increasing the frequency in a range of 30 kHz–200 kHz.The temperature and composition dependences of the dielectric constant and AC conductivity are also studied.The increase of temperature raises the dielectric constant because it increases ionic response to the field at any particular frequency.

First-principles research on influence of C dopants on magnetic and electric properties of rocksalt MgS

The 2×2× 1 rocksalt C-doped MgS supercells are optimized and their magnetic and electric properties, including the half-metallicity, the conductivity and the supercell magnetic moments, are calculated or analysed by the first- principles researches based on the density functional theory. Results show that the concentration of C-dopants may cause important influence on the magnetic and the electric properties of rocksalt MgS. C dopants are inclined to have a scattering distribution. MGC0.0625S0.9375^, aMgC0.1250S0.8750 and MgC0.1875S0.8125 have evident half-metallicity. They have wide spin energy gaps, thus high Curie temperature possibly. Their supercell magnetic moments are near to integral numbers 2.0, 4.0 and 6.0μB. The main reason for spin polarization and half-metallicity of C-doped MgS is that there are sp hybridized orbitals in ligand compound ML6 caused by covalent interaction between C-ions and Mg-ions.

Thermoelectric properties of Al substituted misfit cobaltite Ca_3(Co_(1-x)Al_x)_4O_9 at low temperature

Thermoelectric properties of Al substituted compounds Ca3（Co1-xAlx）4O9 （x=0, 0.03, 0.05）, prepared by a sol-gel process, have been investigated in the temperature range 305-20 K. The results indicate that after Al substitution for Co in Ca3（Co1-xAlx）4O9, the direct current electrical resistivity and thermopower increase due to the reduction of carrier concentration. Experiments show that Al substitution results in decreased lattice thermal conductivity. The figure of merit of temperature behavior suggests that Ca3（Co0.97Al0.03）4O9 would be a promising candidate thermoelectric material for high-temperature thermoelectric application.

Structure and Electric Properties of (1-x)(Bi_(1/2)Na_(1/2)) TiO_3-xBaTiO_3 Systems

The structural, dielectric and piezoelectric properties of （1-x）（Bi1/2Na1/2） TiO3-xBaTiO3 ceramics were investigated for the compositional range, x=0.02, 0.04, 0.06, 0.08, 0.10. The samples were synthesized by a conventional solid-state reaction technique. All compositions show a single perovskite structure, and X-ray powder diffraction patterns can be indexed using a rhombohedral structure. Lattice constants and lattice distortion increase while the amount of BaTiO3 increases. The X-ray diffraction results show the morphotropic phase boundary （MPB） of （1-x）（Bi1/2Na12） TiO3-xBaTiO3 exists in near x=0.06-0.08. Temperature dependence of dielectric constant eT33/ε0 measurement reveals that all compositions experience one structural phase and two ferroelectric phases transition below 400℃： rhombohedral （or rhombohedral plus tetragonal） ferroelectric phase ←→ tetragonal antiferroelectric phase ←→ tetragonal paraelectric phase. Relaxor behaviors exist in the course of ferroelectric to antiferroelectric phase transition. Dielectric and piezoelectric properties are enhanced in the MPB range for （ 1-x）（Bi1/2Na1/2）TiO3-xBaTiO3.

Synthesis and High Temperature Thermoelectric Properties of Ca_(2.7-x)Er_(0.3)Na_xCo_4O_(9+δ)

Polycrystalline Ca2.7-xEr0.3NaxCo4O9+δ (x=0, 0.05, 0.1, 0.15) samples were prepared using a sol-gel process followed by hot-pressing technique sintering and their high-temperature thermoelectric properties were measured from 350 up to 1073 K. The results showed that with the increase of the dopant amount of Na, the electrical conductivity increased, while the Seebeck coefficient and thermal conductivity decreased. The electrical conductivity was dominated by polaron hopping conductivity mechanism above about 550 K and the Na+ substitution for Ca2+ could not change the transport mechanism. The dimensionless figure of merit ZT value reaches 0.31 for Ca2.55Er0.3Na0.15Co4O9+δ at 1073 K, which suggested that Ca2.7-xEr0.3NaxCo4O9+δ (x=0, 0.05, 0.1, 0.15) were good potential oxides for thermoelectric application.

Slight Co-doping tuned magnetic and electric properties on cubic BaFeO_(3) single crystal

The single crystal of cubic perovskite BaFeO3 shows multiple magnetic transitions and external stimulus sensitive magnetism.In this paper,a 5%-Co-doped BaFeO_(3)(i.e.BaFe_(0.95)Co_(0.05)O_(3))single crystal was grown by combining floating zone methods with high-pressure techniques.Such a slight Co doping has little effect on crystal structure,but significantly changes the magnetism from the parent antiferromagnetic ground state to a ferromagnetic one with the Curie temperature TC≈120 K.Compared with the parent BaFeO3 at the induced ferromagnetic state,the saturated magnetic moment of the doped BaFe_(0.95)Co_(0.05)O_(3) increases by about 10%and reaches 3.64μB/f.u.Resistivity and specific heat measurements show that the ferromagnetic ordering favors metallic-like electrical transport behavior for BaFe_(0.95)Co_(0.05)O_(3).The present work indicates that Co-doping is an effective method to tune the magnetic and electric properties for the cubic perovskite phase of BaFeO_(3).

Excellent thermal stability and thermoelectric properties of Pnma-phase SnSe in middle temperature aerobic environment

SnSe is considered to be a promising thermoelectric material due to a high ZT value and abundant and non-toxic composition elements.However,the thermal stability is an important issue for commercial application.In particular,thermoelectric materials are in the high temperature for a long time due to the working condition.The present work investigates the thermal stability and oxidation resistance of single crystal SnSe thermoelectric materials.The scanning electron microscopy(SEM)and transmission electron microscopy(TEM)results show that the internal of SnSe crystal is not easily oxidized,while the x-ray photoelectron spectroscopy(XPS)results indicate that the surface of SnSe is slight oxidized to SnO_(2).Even if the surface is oxidized,the SnSe crystal still exhibits stable thermoelectric properties.Meanwhile,the crystallization quality of SnSe samples can be improved after the appropriate heat treatment in the air,which is in favor of the carrier mobility and can improve the electrical conduction properties of SnSe.Moreover,the decrease of defect density after heat treatment can further improve the Seebeck coefficient and electrical transport properties of SnSe.The density functional theory(DFT)calculation verifies the important role of defect on the electrical conductivity and electron configuration.In summary,appropriate temperature annealing is an effective way to improve the transmission properties of SnSe single crystal thermoelectric materials.

Dielectric properties of nucleated erythrocytes as simulated by the double spherical-shell model

The dielectric properties of nucleated erythrocytes from bullfrogs were measured in a frequency range of 10 kHz–110 MHz.The complex permittivity(ε*),complex conductivity(κ*),and complex resistivity(ρ*)were analyzed and compared in the 10.63%to 37.58%haematocrit(Hct)range.The relaxation behavior,the passive electrical properties,and the cellular structure parameters,including the cell membrane,the cytoplasm,the nuclear membrane,and the nucleoplasm of the nucleated erythrocyte suspensions were investigated.The method used is based on the binomial Cole–Cole equation and the double spherical-shell physical models.Upon the elimination of the electrode polarization effect,two definite relaxations related to the interfacial polarization are observed on low-and high-frequency dispersions.The permittivity values and the characteristic frequency values differ by one order of magnitude:the low-frequency relaxation increments[?ε1=(5.63±1.43)×103]and the characteristic frequency[fc1=(297.06±14.48)kHz]derived from the cell membrane,the high-frequency relaxation increments[?ε2=(5.21±1.20)×102]and the characteristic frequency[fc2=(3.73±0.06)MHz]derived from the dielectric response to the external electric field of the nuclear membrane,respectively.Moreover,the other core dielectric parameters,such as the relative permittivity of the cell membrane[εm=(7.57±0.38)]and the nuclear envelope[εne=(23.59±4.39)],the conductivity of the cytoplasm(hemoglobin,κHb=(0.50±0.13)S/m]and the nuclear endoplasm[κnp=(2.56±0.75)S/m],and the capacitance of the bilayer membranes[Cm:(0.84±0.04)μF/cm2],and Cne:(0.52±0.10)μF/cm2]were also accurately and reliably measured.This work presents a feasible method to evaluate the dielectric parameters and the cellular structure of the erythrocytes of bullfrogs.Moreover,it paves the way for new studies on the haematology of frogs and the detection of nucleated cells via dielectric impedance spectroscopy.