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1.
Cu0.003Bi0.4Sb1.6Te3 alloys were prepared by using encapsulated melting and hot extrusion (HE). The hot-extruded specimens had the relative average density of 98%. The (00l) planes were preferentially oriented parallel to the extrusion direction, but the specimens showed low crystallographic anisotropy with low orientation factors. The specimens were hot-extruded at 698 K, and they showed excellent mechanical properties with a Vickers hardness of 76 Hv and a bending strength of 59 MPa. However, as the HE temperature increased, the mechanical properties degraded due to grain growth. The hot-extruded specimens showed positive Seebeck coefficients, indicating that the specimens have p-type conduction. These specimens exhibited negative temperature dependences of electrical conductivity, and thus behaved as degenerate semiconductors. The Seebeck coefficient reached the maximum value at 373 K and then decreased with increasing temperature due to intrinsic conduction. Cu-doped specimens exhibited high power factors due to relatively higher electrical conductivities and Seebeck coefficients than those of undoped specimens. A thermal conductivity of 1.00 Wm?1 K?1 was obtained at 373 K for Cu0.003Bi0.4Sb1.6Te3 hot-extruded at 723 K. A maximum dimensionless figure of merit, ZT max = 1.05, and an average dimensionless figure of merit, ZT ave = 0.98, were achieved at 373 K. 相似文献
2.
A. A. Kudryashov V. G. Kytin R. A. Lunin V. A. Kulbachinskii A. Banerjee 《Semiconductors》2016,50(7):869-875
The Shubnikov–de Haas effect and the Hall effect in n-Bi2–xTlxSe3 (x = 0, 0.01, 0.02, 0.04) and p-Sb2–xTlxTe3 (x = 0, 0.005, 0.015, 0.05) single crystals are studied. The carrier mobilities and their changes upon Tl doping are calculated by the Fourier spectra of oscillations. It is found shown that Tl doping decreases the electron concentration in n-Bi2–xTlxSe3 and increases the electron mobility. In p-Sb2–xTlxTe3, both the hole concentration and mobility decrease upon Tl doping. The change in the crystal defect concentration, which leads to these effects, is discussed. 相似文献
3.
P. P. Konstantinov L. V. Prokof’eva Yu. I. Ravich M. I. Fedorov V. V. Kompaniets 《Semiconductors》2004,38(7):778-781
Electrical and thermoelectric properties of a lightly doped n-Bi2Te2.7Se0.3 solid solution have been studied in the temperature range 77–300 K. The results are compared with data for the compound PbTe0.9Se0.1 with a similar magnitude of the Seebeck coefficient S at 84 K. Along with lower thermal conductivity, Bi2Te2.7Se0.3 has a higher electrical conductivity σ and a much weaker temperature dependence. As a result, the power coefficient S
2σ in optimal samples begins to decrease only when the density of minority carriers becomes significant. In this case, |S| considerably exceeds the standard value of 200 μV/K. The reduction of the electron density reduces the thermoelectric figure
of merit Z at its maximum and slightly lowers the temperature of the maximum; therefore, the expected effect on the average value of
Z in the range 77–300 K is absent. Similar behavior is observed in Bi2Te2.88Se0.12, although the effect is less pronounced. The experimental results are discussed taking into account possible changes in the
dominant scattering mechanisms, carrier density, and electron energy spectrum.
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Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 38, No. 7, 2004, pp. 811–815.
Original Russian Text Copyright ? 2004 by Konstantinov, Prokof’eva, Ravich, Fedorov, Kompaniets. 相似文献
4.
Avula Edukondalu T. Sripathi Shaik Kareem Ahmmad Syed Rahman K. Sivakumar 《Journal of Electronic Materials》2017,46(2):808-816
Glass with compositions xK2O-(30 ? x)Li2O-10WO3-60B2O3 for 0 ≤ x ≤ 30 mol.% have been prepared using the normal melt quenching technique. The optical reflection and absorption spectra were recorded at room temperature in the wavelength range 300–800 nm. From the absorption edge studies, the values of the optical band gap (E opt) and Urbach energy (ΔE) have been evaluated. The values of E opt and ΔE vary non-linearly with composition parameter, showing the mixed alkali effect. The dispersion of the refractive index is discussed in terms of the single oscillator Wemple Di-Domenico model. 相似文献
5.
Sintered Bi0.5(Na0.8K0.2)0.5TiO3 + x wt.% ZnO nanoparticle (BNKT–xZnOn) ceramics have been fabricated by conventional annealing with the aid of ultrasound waves for preliminary milling. Because of the presence of the liquid Bi2O3–ZnO phase at the eutectic point of 738°C, the sintering temperature decreased from 1150°C to 1000°C, and the morphology phase boundary of BNKT–xZnOn ceramics can be clarified by two separated peaks at (002)T and (200)T of 2θ in the x-ray diffraction (XRD) patterns. The improvement of ferroelectric properties has been obtained for BNZT–0.2 wt.% ZnOn ceramics by the increase of remanent polarization up to 20.4 μC/cm2 and a decrease of electric coercive field down to 14.2 kV/cm. The piezoelectric parameters of the ceramic included a piezoelectric charge constant of d 31 = 78 pC/N; electromechanical coupling factors k p = 0.31 and k t = 0.34, larger than the values of 42 pC/N, 0.12 and 0.13, respectively, were obtained for the BNKT ceramics. 相似文献
6.
Tianxiang Yan Shaokai Ren Xing Ma Feifei Han Liang Fang Biaolin Peng Laijun Liu Xiaojun Kuang Brahim Elouadi 《Journal of Electronic Materials》2018,47(12):7106-7113
(1???x)K0.5Na0.5NbO3-x(Bi0.5K0.5)ZrO3 [abbreviated as (1???x)KNN-xBKZ, 0?≤?x?≤?0.08] lead-free ceramics have been fabricated by a solid-state processing route. Based on the x-ray diffraction data and temperature-dependent dielectric characteristics, an orthorhombic phase for x?≤?0.03 and single rhombohedral one for x?≥?0.05 at room temperature were determined. The cell volume firstly increases, then decreases and finally increases with increasing BKZ, depending on ionic size and crystallographic structure. For the sample of x?=?0.05, a temperature-stable high permittivity (~?1736?±?15%) along with low dielectric loss tangent (≤?5%) is recorded from 158°C to 407°C. In addition, the activation energies of dielectric relaxation and dc conductivity at high temperatures were characterized by impedance spectroscopy. A combined effect of lattice distortion and oxygen vacancies on the magnitude of activation energies was discussed. 相似文献
7.
In single crystals of copper-doped and undoped Bi2Te2.85Se0.15 solid solutions with an electron concentration close to 1 × 1019 cm?3, the temperature dependences are investigated for the Hall (R 123, R 321) and Seebeck (S 11) kinetic coefficients, the electrical-conductivity (σ 11), Nernst-Ettingshausen (Q 123), and thermalconductivity (k 11) coefficients in the temperature range of 77–400 K. The absence of noticeable anomalies in the temperature dependences of the kinetic coefficients makes it possible to use the one-band model when analyzing the experimental results. Within the framework of the one-band model, the effective mass of density of states (m d ≈ 0.8m 0), the energy gap (εg ≈ 0.2 eV), and the effective scattering parameter (r eff ≈ 0.2) are estimated. The obtained value of the parameter r eff is indicative of the mixed electron-scattering mechanism with the dominant scattering by acoustic phonons. Data on the thermal conductivity and the lattice resistivity obtained by subtracting the electron contribution according to the Wiedemann-Franz law are presented. 相似文献
8.
Tasuku Sakuma Shunsuke Nishino Masanobu Miyata Mikio Koyano 《Journal of Electronic Materials》2018,47(6):3177-3183
Transition-metal trichalcogenides MX3 (M = Ti, Zr, Nb, Ta; X = S, Se) are well-known inorganic quasi-one-dimensional conductors. Among them, we have investigated the thermoelectric properties of titanium trisulfide TiS3 microribbon. The electrical resistivity ρ, thermal conductivity κ, and thermoelectric power S were measured using 3ω method. The weight mean values were found to be ρ = 5 mω m and κ = 10 W K?1 m?1 along the one-dimensional direction (b-axis) of the TiS3 microribbon. Combined with the thermoelectric power S = ?530 μV K?1, the figure of merit was calculated as ZT = 0.0023. This efficiency is the same as that of randomly oriented bulk TiS3. We also estimated the anisotropy of σ and κ using the present results and those for randomly oriented bulk material. The obtained weak anisotropy for TiS3 is attributable to strong coupling between triangular columns consisting of TiS3 units. These experimental results are consistent with theoretical results obtained using density functional theory (DFT) calculations. 相似文献
9.
Nd/Nb-co-substituted Bi3.15Nd0.85Ti3?x Nb x O12 (BNTN x , x = 0.01, 0.03, 0.05 and 0.07) thin films were grown on Pt/Ti/SiO2/Si (100) substrates by chemical solution deposition. The effects of Nb content on the micro-structural, dielectric, ferroelectric, leakage current and capacitive properties of the BNTN x thin films were investigated. A low-concentration substitution with Nb ions in BNTN x can greatly enhance its remanent polarization (2P r) and reduce the coercive field (2E c) compared with those of Bi4Ti3O12 (BIT) thin film. The highest 2P r (71.4 μC/cm2) was observed in the BNTN0.03 thin film when the 2E c was 202 kV/cm. Leakage currents of all the films were on the order of 10?6 to 10?5 A/cm2, and the BNTN0.03 thin film has a minimum leakage current (2.1 × 10?6 A/cm2) under the high electric field (267 kV/cm). Besides, the C–V curve of the BNTN0.03 thin film is the most symmetrical, and the maximum tunability (21.0%) was also observed in this film. The BNTN0.03 thin film shows the largest dielectric constant and the lowest dielectric loss and its maximum Curie temperature is 410 ± 5°C. 相似文献
10.
The magnetic susceptibility of Czochralski-grown single crystals of Bi2Te3-Sb2Te3 alloys containing 0, 10, 25, 40, 50, 60, 65, 70, 80, 90, 99.5, or 100 mol % Sb2Te3 has been investigated. The magnetic susceptibility of these crystals was determined at the temperature T = 291 K and the magnetic field H oriented parallel (χ‖) and perpendicularly (χ⊥) to the trigonal crystallographic axis C 3. A complicated concentration dependence of the anisotropy of magnetic susceptibility χ‖/χ⊥ has been revealed. The crystals with the free carrier concentration p ≈ 5 × 1019 cm?3 do not exhibit anisotropy of magnetic susceptibility. The transition to the isotropic magnetic state occurs for the compositions characterized by a significantly increased (from 200 to 300 meV) optical bandgap. 相似文献
11.
The results of investigations of electrical, optical, and photoelectric properties of CdIn2Te4 crystals, which were grown by the Bridgman method are presented. It is shown that electrical conductivity is determined mainly by electrons with the effective mass mn = 0.44m0 and the mobility 120–140 cm2/(V s), which weakly depends on temperature. CdIn2Te4 behaves as a partially compensated semiconductor with the donor-center ionization energy Ed = 0.38 eV and the compensation level K = Na/Nd = 0.36. The absorption-coefficient spectra at the energy hν < Eg = 1.27 eV are subject to the Urbach rule with a typical energy of 18–25 meV. The photoconductivity depends on the sample thickness. The diffusion length, the charge-carrier lifetime, and the surface-recombination rate are determined from the photoconductivity spectra. 相似文献
12.
P. Poopanya A. Yangthaisong C. Rattanapun A. Wichainchai 《Journal of Electronic Materials》2011,40(5):987-991
The doping level dependence of thermoelectric properties of delafossite CuAlO2 has been investigated in the constant scattering time (τ) approximation, starting from the first principles of electronic structure. In particular, the lattice parameters and the energy band structure were calculated using the total energy plane-wave pseudopotential method. It was found that the lattice parameters of CuAlO2 are a = 2.802 Å and c = 16.704 Å, and the internal parameter is u = 0.1097. CuAlO2 has an indirect band gap of 2.17 eV and a direct gap of 3.31 eV. The calculated energy band structures were then used to calculate the electrical transport coefficients of CuAlO2. By considering the effects of doping level and temperature, it was found that the Seebeck coefficient S(T) increases with increasing acceptor doping (A d) level. The values of S(T) in our experiments correspond to an A d level at 0.262 eV, which is identified as the Fermi level of CuAlO2. Based on our experimental Seebeck coefficient and the electrical conductivity, the constant relaxation time is estimated to be 1 × 10?16 s. The power factor is large for a low A d level and increases with temperature. It is suggested that delafossite CuAlO2 can be considered as a promising thermoelectric oxide material at high doping and high temperature. 相似文献
13.
Toshiyuki Takizawa Satoshi Nakazawa Tetsuzo Ueda 《Journal of Electronic Materials》2008,37(5):628-634
Surface passivation by SiN x films is indispensable for high-power operation of AlGaN/GaN heterojunction field-effect transistors (HFETs) since it can effectively suppress collapse in the drain current. So far, the plasma-enhanced chemical vapor deposition technique has been used for the SiN x deposition; however, possible damage induced by the plasma processing may affect direct-current performance or reliability. In this paper, we present subsequent deposition of SiN x ultrathin films on AlGaN/GaN in the same metalorganic chemical vapor deposition reactor. It is experimentally found that this in situ SiN x passivation doubles the sheet carrier density at the AlGaN/GaN interface from that of the unpassivated sample. High-resolution cross-sectional transmission electron microscopy reveals that in situ SiN x is crystallized on the AlGaN layer as island-like structures via the Stranski-Krastanov growth mode. The lattice constants of in situ SiN x are estimated to be a ≈ 3.2 Å and c ≈ 2.4 Å, which are quite different from those of well-known Si3N4 crystal structures. First-principles calculation predicts that the crystal structure of in situ SiN x is the defect wurtzite structure, which well explains the experimental results. The passivation technique using crystalline SiN x films would be promising for high-power and high-frequency applications of AlGaN/GaN HFETs. 相似文献
14.
A BiCu2PO6 microwave dielectric ceramic was prepared using a solid-state reaction method. As the sintering temperature increased from 800°C to 880°C, the bulk density of BiCu2PO6 ceramic increased from 6.299 g/cm3 to 6.366 g/cm3; the optimal temperature was 860°C. The best microwave dielectric properties [permittivity (? r ) = ~16, a quality factor (Q × f) = ~39,110 GHz and a temperature coefficient of resonant frequency (τ f ) = ~?59 ppm/°C] were obtained in the ceramic sintered at 860°C for 2 h. Then, TiO2 with a positive τ f (~+400 ppm/°C) was added to compensate the τ f value. The composite material was found to have a near-zero τ f (+2.7 ppm/°C) and desirable microwave properties (? r = 19.9, Q × f = 24,885 GHz) when synthesized at a sintering temperature of 880°C. This system could potentially be used for low-temperature co-fired ceramics technology applications. 相似文献
15.
Anbalagan Ramakrishnan Sankar Raman Li-Chyong Chen Kuei-Hsien Chen 《Journal of Electronic Materials》2018,47(6):3091-3098
A series of Sn added TiS2 (TiS2:Sn x ; x = 0, 0.05, 0.075 and 0.1) were prepared by solid state synthesis with subsequent annealing. The Sn atoms interacted with sulfur atoms in TiS2 and formed a trace amount of misfit layer (SnS)1+m(TiS2?δ)n compound with sulfur deficiency. A significant reduction in electrical resistivity with moderate decrease in the Seebeck coefficient was observed in Sn added TiS2. Hence, a maximum power factor of 1.71 mW/m-K2 at 373 K was obtained in TiS2:Sn0.05. In addition, the thermal conductivity was decreased with Sn addition and reached a minimum value of 2.11 W/m-K at 623 K in TiS2:Sn0.075, due to the impurity phase (misfit phase) and defects (excess Ti) scattering. The zT values increased from 0.08 in pristine TiS2 to an optimized value of 0.46 K at 623 K in TiS2:Sn0.05. 相似文献
16.
AC Electrical Conductivity of FeIn<Subscript>2</Subscript>Se<Subscript>4</Subscript> Single Crystals
The results obtained in a study of the frequency and temperature dependences of the ac electrical conductivity of FeIn2Se4 single crystals are presented. It is found that the law σ ~ f S (0.1 ≤ S ≤ 1.0) is obeyed for electrical conductivity in the 295–375 K temperature range at frequencies of 2 × 104–106 Hz. It shown that the frequency dependence of the conductivity in an FeIn2Se4 single crystal can be accounted for in terms of the multiplet model, and, consequently, the conductivity in these single crystals is characterized by the band-hopping mechanism. 相似文献
17.
M. N. Solovan A. I. Mostovyi V. V. Brus E. V. Maistruk P. D. Maryanchuk 《Semiconductors》2016,50(8):1020-1024
n-TiN/p-Hg3In2Te6 heterostructures are fabricated by depositing a thin n-type titanium nitride (TiN) film onto prepared p-type Hg3In2Te6 plates using reactive magnetron sputtering. Their electrical and photoelectric properties are studied. Dominant charge-transport mechanisms under forward bias are analyzed within tunneling-recombination and tunneling models. The fabricated n-TiN/p-Hg3In2Te6 structures have the following photoelectric parameters at an illumination intensity of 80 mW/cm2: the open-circuit voltage is VOC = 0.52 V, the short-circuit current is ISC = 0.265 mA/cm2, and the fill factor is FF = 0.39. 相似文献
18.
A. V. Savitskii O. A. Parfenyuk M. I. Ilashchuk K. S. Ulyanitskii S. N. Chupyra N. D. Vakhnyak 《Semiconductors》2005,39(7):754-758
The electrical properties in the temperature range 295–430 K and low-temperature (4.2 K) photoluminescence of Cd1?xZnxTe:Cl semi-insulating crystals grown from melts with a variable impurity content (C Cl 0 = 5 × 1017–1 × 1019 cm?3) are investigated. Nonequilibrium processes leading to a decrease in carrier concentration are observed in all the samples at low temperatures (T = 330–385 K). These changes are reversible. The activation energy of these processes E a is found to be 0.88 eV. As with semi-insulating CdTe:Cl, the observed phenomena can be explained by a change in the charge state of background copper atoms: CuCd ? Cui. The introduction of Zn changes the ratio of the concentrations of shallow-level donors Cui and ClTe from their levels in the initial material. 相似文献
19.
Electrical properties of a p+-Bi2Te3-p-GaSe isotype heterostructure fabricated for the first time are reported. A qualitative model is suggested which explains the emergence of negative differential conductivity for a forward-biased structure and for a reverse-biased structure, which is also illuminated. 相似文献
20.
The photoluminescence properties of thallium-containing vitreous semiconductor systems with stoichiometric and nonstoichiometric compositions (GeSe2)1–x Tl x and (GeSe3)1–x Tl x (0 ? x ? 0.1) are studied at a temperature of T = 77 K. Intrinsic defects with negative correlation energy are responsible for the Gaussian shape of the photoluminescence spectra. It is established that an increase in x in the systems does not affect the shape of the spectrum, does not generate new emission bands, shifts the photoluminescence spectra to the region of low energies, reduces the intensity of radiation, and increases its half-width. Kinetics of the fatigue of photoluminescence is different for both systems and is characterized by one curve irrespective of Tl content in the systems. 相似文献