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1.
A series of ZnO1−xSx alloy films (0 ≤ x ≤ 1) were grown on quartz substrates by radio-frequency (rf) magnetron sputtering of ZnS ceramic target, using oxygen and argon as working gas. X-ray diffraction measurement shows that the ZnO1−xSx films have wurtzite structure with (0 0 2) preferential orientation in O-rich side (0 ≤ x ≤ 0.23) and zinc blende structure with (1 1 1) preferential orientation in S-rich side (0.77 ≤ x ≤ 1). However, when the S content is in the range of 0.23 < x < 0.77, the ZnO1−xSx film consists of two phases of wurtzite and zinc blende or amorphous ZnO1−xSx phase. The band gap energy of the films shows non-linear dependence on the S content, with an optical bowing parameter of about 2.9 eV. The photoluminescence (PL) measurement reveals that the PL spectrum of the wurtzite ZnO1−xSx is dominated by visible band and its PL intensity and intensity ratio of UV to visible band decrease greatly compared with undoped ZnO. All as-grown ZnO1−xSx films behave insulating, but show n-type conductivity for w-ZnO1−xSx and maintain insulating properties for β-ZnO1−xSx after annealed. Mechanisms of effects of S on optical and electrical properties of the ZnO1−xSx alloy are discussed in the present work. 相似文献
2.
N. El-Kabany 《Physica B: Condensed Matter》2012,407(5):817-821
Bulk InxSe1−x (with x=5-25 at%) glasses were prepared using the melt-quench technique. Short range order(SRO) was examined by the X-ray diffraction using Cu(kα) radiation in the wave vector interval 0.28≤k≤6.5 A0−1.The SRO parameters have been obtained from the radial distribution function. The inter-atomic distance obtained from the first and second peak are r1=0.263 and r2=0.460 nm, which is equivalent In-Se and Se-Se bond length. The fundamental structural unit for the studied glasses is In2Se3 pyramid. Using the differential scanning calorimetry (DSC), the crystallization mechanism of InxSe1−x chalcogenide glass has been studied. The glass transition activation energy (Eg) is 289±0.3 kj/mol.There is a correlation amongst the glass forming ability, bond strength and the number of lone pair electrons. The utility of the Gibbs-Di Marzio relation was achieved by estimating Tg theoretically. 相似文献
3.
B.S. WangC.C. Li S. LinJ.C. Lin L.J. LiP. Tong W.J. LuX.B. Zhu Z.R. YangW.H. Song J.M. DaiY.P. Sun 《Journal of magnetism and magnetic materials》2011,323(15):2017-2022
We report the effects of Al doping on the structure, magnetic properties, and magnetocaloric effect of antiperovskite compounds Ga1−xAlxCMn3 (0≤x≤0.15). Partial substitutions of Al for Ga enhance the Curie temperature (from 250 K for x=0.0 to 312 K for x=0.15) and the saturation magnetization. On increasing the doping level x, the maximum values of the magnetic entropy change (−ΔSM) decreases while the temperature span of −ΔSM vs. T plot broadens. Furthermore, the relative cooling power (RCP) is also studied. For 20 kOe, the RCP value tends to saturate at a high doping level (for x=0.12, 119 J/kg at 296 K). However, at 45 kOe, the RCP value increases quickly with increasing x (for x=0.15, 293 J/kg at 312 K). Considering the relatively large RCP and inexpensive raw materials, Ga1−xAlxCMn3 may be alternative candidates for room-temperature magnetic refrigeration. 相似文献
4.
BiFeO3/Zn1−xMnxO (x = 0-0.08) bilayered thin films were deposited on the SrRuO3/Pt/TiO2/SiO2/Si(1 0 0) substrates by radio frequency sputtering. A highly (1 1 0) orientation was induced for BiFeO3/Zn1−xMnxO. BiFeO3/Zn1−xMnxO thin films demonstrate diode-like and resistive hysteresis behavior. A remanent polarization in the range of 2Pr ∼ 121.0-130.6 μC/cm2 was measured for BiFeO3/Zn1−xMnxO. BiFeO3/Zn1−xMnxO (x = 0.04) bilayer exhibits a highest Ms value of ∼15.2 emu/cm3, owing to the presence of the magnetic Zn0.96Mn0.04O layer with an enhanced Ms value. 相似文献
5.
M.A. AliA.K.M.A. Islam 《Physica B: Condensed Matter》2012,407(6):1020-1026
The structural, elastic, electronic and optical (x=0) properties of doped Sn1−xBixO2 and Sn1−xTaxO2 (0≤x≤0.75) are studied using the first-principles pseudopotential plane-wave method within the local density approximation. The independent elastic constants Cij and other elastic parameters of these compounds have been calculated for the first time. The mechanical stability of the compounds with different doping concentrations has also been studied. The electronic band structure and density of states are calculated and the effect of doping on these properties is also analyzed. It is seen that the band gap of the undoped compound narrowed with dopant concentration, which disappeared for x=0.26 for Bi doping and 0.36 for Ta doping. The materials thus become conductive oxides through the change in the electronic properties of the compound for x≤0.75, which may be useful for potential application. The calculated optical properties, e.g. dielectric function, refractive index, absorption spectrum, loss-function, reflectivity and conductivity of the undoped SnO2 in two polarization directions are compared with both previous calculations and measurements. 相似文献
6.
Structural, electronic and optical properties as well as structural phase transitions of ternary alloy CdxZn1 − xS have been investigated using the first-principles calculations based on the density functional theory. We found that the crystal structure of CdxZn1 − xS alloys transforms from wurtzite to zinc blende as Cd content of x=0.83. Effect of Cd content on electronic structures of CdxZn1 − xS alloys has been studied. The bandgaps of CdxZn1 − xS alloys with wurtzite and zinc blende structures decrease with the increase of Cd content. Furthermore, dielectric constant and absorption coefficient also have been discussed in detail. 相似文献
7.
M.M. El-Nahass M.A.M. Seyam H.E.A. El-Sayed A.M. Abd El-Barry 《Applied Surface Science》2006,252(18):6218-6227
Thin films of samples of the glassy SxSe100−x system with 0 ≤ x ≤ 7.28 have been prepared by thermal evaporation technique at room temperature (300 K). X-ray investigations show that the structure of pure selenium (Se) does change seriously by the addition of small amount of sulphur S ≤7.28%. The lattice parameters were determined as a function of sulphur content. Results of differential thermal analysis (DTA) of the glassy compositions of the system SxSe100−x were discussed. The characteristic temperatures (Tg, Tc and Tm) were evaluated. Dark electrical resistivities, ρ, of SxSe100−x thin films with different thicknesses from 100 to 500 nm, were measured in the temperature range from 300 to 423 K. Two distinct linear parts with different activation energies were observed. The variation of electrical resistivity of examined compositions has been discussed as a function of the film thickness, temperature and the sulphur content. The application of Mott model for the phonon assisted hopping of small polarons gave the same two activation energies obtained from the resistivity temperature calculations. 相似文献
8.
Zn1−xGdxS (x = 0.00, 0.02 and 0.04) nanoparticles were synthesized by facile chemical co-precipitation method using PVP as a surfactant. ZnS nanoparticles could be doped with Gd ions during synthesis without altering the XRD patterns of ZnS. Also, the pattern of the powders showed cubic zincblende structure. The particle size obtained from the XRD studies lies in the range 3-5 nm, whereas from TEM analysis it is 4 nm for x = 0.02 sample. The UV-Vis absorption spectra revealed that Zn1−xGdxS nanoparticles exhibit strong confinement effect as the blue shift in the absorption spectra with that of the undoped ZnS. The photoluminescence spectra showed enhanced luminescence intensity and the entry of Gd into host lattice. 相似文献
9.
Intense red phosphors, AgGd1−xEux(W1−yMoy)2O8 (x=0.0-1.0, y=0.0-1.0), have been synthesized through traditional solid-state reaction and characterized by X-ray diffraction (XRD) and photoluminescence (PL). XRD results reveal that AgGd1−xEuxW2O8 synthesized at 1000 °C has a tetragonal crystal structure, which is named as high temperature phase (HTP) AgGdW2O8. All phosphors compositions with Eu3+ show red and green emission on excitation either in the charge-transfer or Eu3+ levels. Analysis of the emission spectra with different Eu3+ concentrations reveal that the optimum dopant concentration for Eu3+ is x=0.6 in the HTP AgGd1−xEuxW2O8 (x=0.0-1.0). Studies on the AgGd0.4Eu0.6(W1−yMoy)2O8 (y=0.0-1.0) and AgGd1−xEux(W0.7Mo0.3)2O8 (x=0.0-1.0) show that the emission intensity is maximum for compositions with y=0.3 and x=0.5, respectively, and a decrease in emission intensity is observed for higher y or x values. The Mo6+ and Eu3+ co-doped AgGd(WO4)2 phosphors show higher emission intensity in comparison with the singly Eu3+-doped AgGd(WO4)2 in UV region. The intense emission of the tungstate/molybdate phosphors under 394 and 465 nm excitations, respectively, suggests that these materials are promising candidates as red-emitting phosphors for near-UV/blue GaN-based white LED for white light generation. 相似文献
10.
In order to design the optimal component structure of transmission-mode (t-mode) Ga1−xAlxN photocathode, the optical properties and quantum efficiency of Ga1−xAlxN photocathodes are simulated. Based on thin film principle, optical model of t-mode Ga1−xAlxN photocathodes is built. And the quantum efficiency formula is put forward. Results show that Ga1−xAlxN photocathodes can satisfy the need of detectors with “solar blind” property when the Al component is bigger than 0.375. There is an optimal thickness of Ga1−xAlxN layer to get highest quantum efficiency, and the optimal thickness is 0.3 μm. There is close relation between absorptivity and quantum efficiency, which is in good agreement with the “three-step” model. This work gives a reference for the experimental research on the Ga1−xAlxN photocathodes. 相似文献
11.
Tanjore V. Jayaraman Mark A. KotenJeffrey E. Shield 《Journal of magnetism and magnetic materials》2011,323(15):2037-2041
The magnetocaloric properties of melt-spun Gd-B alloys were examined with the aim to explore their potential application as magnetic refrigerants near room temperature. A series of Gd100−xBx (x=0, 5, 10, 15, and 20 at%) alloys were prepared by melt spinning. With the decrease in Gd/B ratio, Curie temperature (TC) remains constant at ∼293 K, and saturation magnetization, at 275 K, decreases from ∼100 to ∼78 emu/g. Negligible magnetic hysteresis was observed in these alloys. The peak value of magnetic entropy change, (−ΔSM)max, decreased from ∼9.9 J/kg K (0-5 T) and ∼5.5 J/kg K (0-2 T) for melt-spun Gd to ∼7.7 J/kg K (0-5 T) and ∼4.0 J/kg K (0-2 T), respectively for melt-spun Gd85B15 and Gd80B20 alloys. Similarly, the refrigeration capacity (q) decreased monotonously from ∼430 J/kg (0-5 T) for melt-spun Gd to ∼330 J/kg (0-5 T) for melt-spun Gd80B20 alloy. The near room temperature magnetocaloric properties of melt-spun Gd100−xBx (0≤x≤20) alloys were found to be comparable to few first-order transition based magnetic refrigerants. 相似文献
12.
R.L. Hadimani P.A. BartlettY. Melikhov J.E. SnyderD.C. Jiles 《Journal of magnetism and magnetic materials》2011,323(5):532-534
Gd5(SixGe1−x)4, known for its giant magnetocaloric effect, also exhibits a colossal strain of the order of 10,000 ppm for a single crystal near its coupled first-order magnetic-structural phase transition, which occurs near room temperature for the compositions 0.41≤x≤0.575. Such colossal strain can be utilised for both magnetic sensor and actuator applications. In this study, various measurements have been carried out on strain as a function of magnetic field strength and as a function of temperature on single crystal Gd5Si2Ge2 (x=0.5), and polycrystalline Gd5Si1.95Ge2.05 (x=0.487) and Gd5Si2.09Ge1.91 (x=0.52). Additionally a giant magnetostriction/thermally induced strain of the order of 1800 ppm in polycrystalline Gd5Si2.09Ge1.91 was observed at its first order phase transition on varying temperature using a Peltier cell without the use of bulky equipment such as cryostat or superconducting magnet. 相似文献
13.
Based on the pseudopotential method under the virtual crystal approximation that takes into account the effect of compositional disorder, the electron and heavy-hole effective masses and the dielectric constants in GaxIn1−xAs (0≤x≤1) have been calculated. The results are firstly used in the Wannier equation, which allowed the determination of the exciton reduced mass, binding energy and Bohr radius; then, the polaron properties have been investigated. In this respect, the Fröhlich coupling parameter, Debye temperature and polaron effective mass are calculated and their dependence on the Ga concentration is examined. For InAs and GaAs, our results are generally in reasonable agreement with the known data in the literature, while for compositions x in the range 0-1, our treatment represents the first theoretical predictions. It is found that the exciton and polaron properties for compositions 0<x<1 differ from those of the parent compounds suggesting thus more diverse opportunities to describe most exciton and polaron properties in ternary mixed crystals of interest. 相似文献
14.
X.R. Zhao W.-Q. Lu Y. Konishi T. Ishibashi Y. Matsumoto T. Hasegawa 《Applied Surface Science》2006,252(7):2628-2633
BixY3−xFe5O12 thin films have been grown on GGG (Gd3Ga5O12) (1 1 1) substrates by the combinatorial composition-spread techniques under substrate temperature (Tsub) ranging from 410 to 700 °C and O2 pressure of 200 mTorr. In order to study the effect of substrates on the deposition of BixY3−xFe5O12 thin films, garnet substrates annealed at 1300 °C for 3 h were also used. Magneto-optical properties were characterized by our home-designed magneto-optical imaging system. From the maps of Faraday rotation angle θF, it was evident that the Faraday effect appears only when Tsub = 430-630 °C. θF reaches to the maximum value (∼6°/μm, λ = 632 nm) at 500 °C, and is proportional to the Bi contents. XRD and EPMA analyses showed that Bi ions are easier to substitute for Y sites and better crystallinity is obtained for annealed substrates than for commercial ones. 相似文献
15.
The samples of Cu1−xPtxFeO2 (0 ≤ x ≤ 0.05) delafossite have been synthesized by solid-state reaction method to investigate their optical and electrical properties. The properties of electrical resistivity and Seebeck coefficient were measured in the high temperature ranging from 300 to 960 K, and the Hall effect and the optical properties were measured at room temperature. The obtained results of Seebeck showed the samples are p-type conductor. The optical properties at room temperature exhibited the samples are transparent visible light material with optical direct gap 3.45 eV. The low electrical resistivity, hole mobility and carrier density at room temperature displayed value ranging from 0.29 to 0.08 Ω cm, 1.8 to 8.6 cm2/V s and 1.56 × 1018 to 4.04 × 1019 cm−3, respectively. The temperature range for transparent visible light is below 820 K because the direct energy gap contains value above 3.1 eV. Consequently, the Cu1−xPtxFeO2 delafossite enhance performance for materials of p-type transparent conducting oxide (TCO) with low electrical resistivity. 相似文献
16.
Akinori Kan Hirotaka OgawaYuki Inami Tohru Moriyama 《Physica B: Condensed Matter》2011,406(17):3170-3174
Bismuth layer-structured (Bi7−xSrx)(Fe3−xTi3+x)O21 (BSFT) ceramics were synthesized and the ferroelectric properties and crystal structure were investigated. X-ray powder diffraction profiles and refinement of the lattice parameters indicated single phase BSFT was obtained in the composition range 0-1.5. The lattice parameter b of BSFT remained almost constant, while a slight decrease in the lattice parameter a was observed by the Sr and Ti substitution for Bi and Fe, respectively, which indicated an increase in the orthorhombicity. The dependence of the BSFT lattice parameter on temperature implied a phase transition from the orthorhombic to the tetragonal phase, which was in good agreement with the Curie temperature. The remnant polarization Pr, of BSFT was significantly improved by the Sr and Ti substitution for Bi and Fe, and ranged from 9 to 16 μC/cm2, although no remarkable variation in the coercive field Ec was observed. As a result, a well-saturated P-E hysteresis loop of BSFT ceramic was obtained at x=0.5 with a Pr of 30 μC/cm at an applied voltage of 280 kV/cm. 相似文献
17.
Shaoxiong LinXin Zhang Xuezhao ShiJinping Wei Daban LuYuzhen Zhang Huanhuan KouChunming Wang 《Applied Surface Science》2011,257(13):5803-5807
In this paper the fabrication and characterization of IV-VI semiconductor Pb1−xSnxSe (x = 0.2) thin films on gold substrate by electrochemical atomic layer deposition (EC-ALD) method at room temperature are reported. Cyclic voltammetry (CV) is used to determine approximate deposition potentials for each element. The amperometric I-t technique is used to fabricate the semiconductor alloy. The elements are deposited in the following sequence: (Se/Pb/Se/Pb/Se/Pb/Se/Pb/Se/Sn …), each period is formed using four ALD cycles of PbSe followed by one cycle of SnSe. Then the deposition manner above is cyclic repeated till a satisfactory film with expected thickness of Pb1−xSnxSe is obtained. The morphology of the deposit is observed by field emission scanning electron microscopy (FE-SEM). X-ray diffraction (XRD) pattern is used to study its crystalline structure; X-ray photoelectron spectroscopy (XPS) of the deposit indicates an approximate ratio 1.0:0.8:0.2 of Se, Pb and Sn, as the expected stoichiometry for the deposit. Open-circuit potential (OCP) studies indicate a good p-type property, and the good optical activity makes it suitable for fabricating a photoelectric switch. 相似文献
18.
Hailing MaiDengsong Zhang Liyi Shi Tingting YanHongrui Li 《Applied Surface Science》2011,257(17):7551-7559
A series of Ce1−xCuxO2 nanocomposite catalysts with various copper contents were synthesized by a simple hydrothermal method at low temperature without any surfactants, using mixed solutions of Cu(II) and Ce(III) nitrates as metal sources. These bimetal oxide nanocomposites were characterized by means of XRD, TEM, HRTEM, EDS, N2 adsorption, H2-TPR and XPS. The influence of Cu loading (5-25 mol%) and calcination temperature on the surface area, particle size and catalytic behavior of the nanocomposites have been discussed. The catalytic activity of Ce1−xCuxO2 nanocomposites was investigated using the test of CO oxidation reaction. The optimized performance was achieved for the Ce0.80Cu0.20O2 nanocomposite catalyst, which exhibited superior reaction rate of 11.2 × 10−4 mmol g−1 s−1 and high turnover frequency of 7.53 × 10−2 s−1 (1% CO balanced with air at a rate of 40 mL min−1, at 90 °C). No obvious deactivation was observed after six times of catalytic reactions for Ce0.80Cu0.20O2 nanocomposite catalyst. 相似文献
19.
Yu-jie Zhang Hong-guo Zhang Hong-wei Zhang Jing-lan Chen Guang-heng Wu 《Journal of magnetism and magnetic materials》2010,322(15):2251-809
A series of rare-earth doped BiFeO3 samples, Bi1−xRxFeO3 (x=0-1, R=La, Nd, Sm, Eu and Tb), were prepared in this work. X-ray diffraction analysis showed that the structure of rare-earth doped BiFeO3 was transformed from rhombohedral lattice to orthorhombic one by increasing x. The lattice constants and unit-cell volume decreased with the increasing of the doping content, while both the Néel temperature and magnetization were enhanced. A magnetic phase transition was observed at about 35 K for BiFeO3. The variation of the magnetization with temperature depended on applied field strength and magnetizing history, which was explained according to the antiferromagnetic exchange interaction between Fe and R sites in Bi1−xRxFeO3(x>0). The magnetocrystalline anisotropy contributed by Fe sublattice gave rise to a large coercivity in BixNd1−xFeO3 with an orthorhombic structure. 相似文献
20.
Z.H. Wang D.Y. Geng J. Li W. Liu Z.D. Zhang 《Journal of magnetism and magnetic materials》2010,322(20):3000-3003
The characterization and magnetic properties of YFe12−xMox (x=2.0, 2.5 and 3.0) with the ThMn12-type structure, and the magnetocaloric effect of YFe9.5Mo2.5 were investigated. A directional growth was observed in YFe10Mo2 alloy. A broad peak in the zero-field-cooling (ZFC) magnetization curve of the YFe12−xMox compounds is ascribed to the existence of ferromagnetic clusters with different site moments and scattered orientations of the moments. The broad range of the peak is reduced with increasing Mo content. A weak peak is observed near 190 K in the ZFC curve of YFe9Mo3, which is associated with the 8i sites being mostly occupied by Mo atoms. YFe9.5Mo2.5 has a magnetic entropy change of −1.09 J/kg K for a field change of 5 T at 277 K. 相似文献