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1.
《Current Applied Physics》2010,10(3):734-739
CdxZn1−xSe films (0  x  1) were deposited for the first time by the pulse plating technique at different duty cycles in the range 6–50% at room temperature from an aqueous bath containing zinc sulphate, cadmium sulphate and selenium oxide. To the author’s knowledge this is the first report on pulse plated CdxZn1−xSe films. The deposition potential was −0.9 V (SCE). The as deposited films exhibited cubic structure. Composition of the films was estimated by Energy Dispersive Analysis of X-ray studies. X-ray photoelectron spectroscopy studies indicated the binding energies corresponding to Zn(2p3/2), Cd(3d5/2 and 3d3/2) and Se(3d5/2 and 3d3/2). Optical band gap of the films varied from 1.72 to 2.70 eV as the composition varied from CdSe to ZnSe side. Atomic force microscopy studies indicated grain size in the range of 20–150 nm.  相似文献   

2.
YFexAl12−x in the composition range 4.4⩽x⩽5 was prepared by induction melting followed by annealing in vacuum at 1270 K. Magnetization data below 150 K show complex magnetic behaviour dependent on applied field, composition and temperature. The transition temperature Tc, corresponding to the main maximum of the magnetization vs. temperature curves and below which magnetic interactions are observed for a significant fraction of the Fe atoms in the Mössbauer spectra, decreases from 180 K for x=4 down to 100 K for 4.2⩽x⩽4.7 and rises again up to 160 K for x=5. The analysis of the spectra obtained at 5 K is consistent with full occupation of the 8f sites by Fe atoms and sharing of the 8j sites by Fe and Al as deduced from the Rietveld analysis of X-ray powder diffraction data. The Mössbauer spectra further show a dependence of magnetic hyperfine fields and isomer shifts on the crystallographic site and on the number of the Fe nearest neighbours similar to that observed in UFexAl12−x (4⩽x⩽6) and RFexAl12−x (R=Y, Lu, x=4, 4.2). The magnetic properties of the UFexAl12−x and YFexAl12−x series are compared and the magnetic interactions between the different Fe sublattices are discussed.  相似文献   

3.
Single crystals of hexagonal HfFe6Ge6-type HoMn6Sn6−xGax compounds (0.14⩽x⩽1.89) have been obtained by a flux method and studied by magnetisation measurements. All the compounds order ferrimagnetically (308⩽Tc⩽386 K) with moments lying in the (0 0 1) plane and undergo a moment reorientation transition at lower temperatures (156⩽TSR⩽195 K). At 5 K, the moments are aligned along an intermediate direction (44⩽φc⩽50°). These results are discussed and compared with the neutron diffraction results related to the isotypic TmMn6Sn6−xGax and TbMn6Sn6−xGax series where a change of the easy direction is observed with increasing gallium contents.  相似文献   

4.
Nanostructured Zn1−xMnxS films (0  x  0.25) were deposited on glass substrates by simple resistive thermal evaporation technique. All the films were deposited at 300 K in a vacuum of 2 × 10−6 m bar. All the films temperature dependence of resistivity revealed semiconducting behaviour of the samples. Hot probe test revealed that all the samples exhibited n-type conductivity. The nanohardness of the films ranges from 4.7 to 9.9 GPa, Young’s modulus value ranging 69.7–94.2 GPa.  相似文献   

5.
The chemical pressure control in (Sr2−xCax)FeMoO6 (0  x  2.0) with double perovskite structure has been investigated systematically. We have performed first-principles total energy and electronic structure calculations for x = 0 and x = 2.0. The increasing Ca content in (Sr2−xCax)FeMoO6 samples increases the magnetic moment close to the theoretical value due to reduction of Fe/Mo anti-site disorder. An increasing Ca content results in increasing (Fe2+ + Mo6+)/(Fe3+ + Mo5+) band overlap rather than bandwidth changes. This is explained from simple ionic size arguments and is supported by X-ray absorption near edge structure (XANES) spectra and band structure calculations.  相似文献   

6.
《Current Applied Physics》2010,10(1):333-336
Observation of room temperature ferromagnetism in Fe doped In2O3 samples (In1−xFex)2O3 (0  x  0.07) prepared by co-precipitation technique is reported. Lattice parameter obtained from powder X software shows distinct shrinkage of the lattice constant indicating an actual incorporation of Fe ions into the In2O3 lattice. X-ray diffraction data measurements show that the entire sample exhibits single phase polycrystalline behavior. SEM micrographs showed the prepared powder was in the range 25–36 nm. SEM EDS mapping showed the presence of Fe and In ions in the Fe doped In2O3 sample. The highest remanence magnetization moment (6.624 × 10−4 emu/g) is reached in the sample with x = 0.03.  相似文献   

7.
Dielectric and piezoelectric properties of [Pb0.976La0.014−xCexSr0.01][Zr0.57Ti0.43](0.9975−((0.014−x)/4)−(x/4))Nb0.002O3 (PLCSZNT) ceramic compositions for 0  x  1 mol% were investigated. The XRD analysis showed the presence of single rhombohedral phase. Grain size and density increased until 0.6 mol% Ce and further Ce concentration inhibited the grain growth. The stability of rhombohedral phase has been supported by tolerance factor and average electronegativity difference. The room temperature dielectric response (εRT) increased up to 0.6 mol% combined with a significantly reduced dielectric loss (Tan δ) and low Curie temperature (Tc). The higher piezoelectric properties associated with low Ce concentration are attributed to rhombohedral phase. The optimum dielectric and piezoelectric properties were found in 0.6 mol% Ce composition which could be suitable for possible piezoelectric applications.  相似文献   

8.
Based on the pseudopotential formalism under the virtual crystal approximation, the dielectric and lattice vibration properties of zinc-blende InAs1−xySbxPy quaternary system under conditions of lattice matching and lattice mismatching to InAs substrates have been investigated. Generally, a good agreement is noticed between our results and the available experimental and theoretical data reported in the literature. The variation of all features of interest versus either the composition parameter x or the lattice mismatch percentage is found to be monotonic and almost linear. The present study provides more opportunities to get diverse high-frequency and static dielectric constants, longitudinal and transversal optical phonon modes and phonon frequency splitting by a proper choice of the composition parameters x and y (0  x  0.30, 0  y  0.69) and/or the lattice mismatch percentage.  相似文献   

9.
Spin reorientation and magnetocrytalline anisotropy of (Nd1−xDyx)2Fe14B (x=0.25, 0.5, 0.75) have been studied from mangetization curves of magnetically aligned powders. In (Nd1−xDyx)2Fe14B, the spin reorientation temperature (TSR) decreases linearly on increasing Dy-substitution from 135 to 56 K with the ratio of ΔTSR=−1.11 K/Dy at% in the composition range of 0⩽x⩽0.75. The spin reorientation angle at 4.2 K decreases on Dy-substitution from 30.4° at x=0 to 14.7° at x=0.75. From the investigation of the magnetocrystalline anisotropy at 4.2 K, the disappearance of the spin reorientation for compositions x≳0.85 is expected.  相似文献   

10.
《Current Applied Physics》2010,10(3):866-870
Perovskite La1−xSrxFeO3 (0.10  x  0.20) ceramics have been synthesized by the conventional solid-state reaction technique. Their electrical resistivity, Seebeck coefficient and thermal conductivity have been measured. It has been found that the increase of Sr content reduces significantly both the electrical resistivity and the Seebeck coefficient, but slightly increases the high-temperature thermal conductivity. An adiabatic hopping conduction mechanism of small polaron is suggested from the analysis of the temperature dependence of the electrical resistivity. Seebeck coefficients decrease with increasing temperature, and saturate at temperature above 573 K. The saturated value of Seebeck coefficient decreases with increasing of Sr contents, from 200 μV/K for x = 0.10 to 100 μV/K for x = 0.20. All samples exhibit lower thermal conductivity with values around 2.6 W/m K. The highest dimensionless figure of merit is 0.031 at temperature 973 K in La0.88Sr0.12FeO3.  相似文献   

11.
《Current Applied Physics》2010,10(3):838-841
The low-temperature conductivity of InxGa1−xN alloys (0.06  x  0.135) is analyzed as a function of indium composition (x). Although our InxGa1−xN alloys were on the metallic side of the metal–insulator transition, neither the Kubo-Greenwood nor Born approach were able to describe the transport properties of the InxGa1−xN alloys. In addition, all of the InxGa1−xN alloys took place below the Ioeffe–Regel regime with their low conductivities. The observed behavior is discussed in the framework of the scaling theory. With decreasing indium composition, a decrease in thermal activation energy is observed. For the metal–insulator transition, the critical indium composition is obtained as xc = 0.0543 for InxGa1−xN alloys.  相似文献   

12.
BTlGaN quaternary alloys are proposed as new semiconductor materials for infrared opto-electronic applications. The structural and opto-electronic properties of zinc blende BxTlyGa1−xyN alloys lattice matched to GaN with (0  x and y  0.187) are studied using density functional theory (DFT) within full-potential linearized augmented plane wave (FP-LAPW) method. The calculated structural parameters such as lattice constant a0 and bulk modulus B0 are found to be in good agreement with experimental data using the new form of generalized gradient approximation (GGA-WC). The band gaps of the compounds are also found very close to the experimental results using the recently developed Tran–Blaha-modified Becke–Johnson (TB-mBJ) exchange potential. A quaternary BxTlyGa1−xyN is expected to be lattice matched to the GaN substrate with concentrations x = 0.125 and y = 0.187 allows to produce high interface layers quality. It has been found that B incorporation into BTlGaN does not significantly affect the band gap, while the addition of dilute Tl content leads to induce a strong reduction of the band gap, which in turn increases the emission wavelengths to the infrared region. The refractivity, reflectivity and absorption coefficient of these alloys were investigated. BTlGaN/GaN is an interesting new material to be used as active layer/barriers in quantum wells suitable for realizing advanced Laser Diodes and Light-Emitting Diodes as new sources of light emitting in the infrared spectrum region.  相似文献   

13.
Spectral sensitivity dependencies of Hg1−xCdxTe (0.20  x  0.25) backside illuminated planar photodiodes were investigated at T = 80 K to study their longwavelength edge features. It was shown that the longwavelength part of these spectral dependencies is mainly formed by the exponential wavelength dependence of the optical transitions. Empirical dependencies of cut-off wavelengths at different values (λmax, λ0.5, λ0.9) were obtained. The influence of the epitaxial layer thickness on the maximum sensitivity position was also studied.  相似文献   

14.
《Solid State Communications》2002,121(9-10):467-470
Using the Korringa–Kohn–Rostoker coherent-potential approximation in the atomic-sphere approximation (KKR-ASA CPA) method for taking into account the effects of disorder, Gaspari–Gyorffy formalism for calculating the electron–phonon coupling constant λ, and Allen–Dynes equation for calculating Tc, we have studied the variation of Tc in Mg1−xTaxB2 alloys as a function of Ta concentration. Our results show that the Tc decreases with the addition of Ta for up to 40 at.% and remains essentially zero from 60 to 80 at.% of Ta. We also find TaB2 to be superconducting, albeit at a lower temperature. Our analysis shows that the variation in Tc in Mg1−xTaxB2 is mostly dictated by the changes in the B p density of states associated with the addition of Ta.  相似文献   

15.
The present work reports the observation of Meyer–Neldel rule for the thermally activated crystallization of glassy Se98−xZn2Inx (0  x  10) alloys. We have observed a strong co-relation between the pre-exponential factor K0 of rate constant K(T) of crystallization and activation energy of crystallization Ec in the present case. This indicates the presence of compensation effect for the non-isothermal crystallization process in the present glassy system, which is explained in terms of phase separation of the present alloys due to flaw bonds of these amorphous solids.  相似文献   

16.
The solid solutions BaAl1−xSi1+x (0  x  0.5) were prepared. The compound with the stoichiometric composition (x = 0) did not show superconductivity as reported by other investigators, but the solid solutions with x > 0 became superconductors with a transition temperature Tc = 2.8 K. The comparison of the lattice parameters with those of the other isotypic ternary superconductors MAlSi (M = Ca, Sr) suggested that the superconductivity could be related to the lattice parameter within the (AlSi) plane rather than the interlayer spacing. The band structures near the Fermi level of MAlSi (M = Ca, Sr, Ba) were measured using soft X-ray photoelectron spectroscopy, which were in good agreement with the calculated ones, confirming that the contribution of the d orbitals of the alkaline-earth metals were predominant in the conduction bands.  相似文献   

17.
《Current Applied Physics》2010,10(4):975-984
Polycrystalline nickel–zinc–copper ferrites with chemical formula Ni0.6+xZn0.2Cu0.2VxFe2−2xO4,(0.0  x  0.25) were prepared by the ceramic route. The X-ray diffraction (XRD) analysis of the samples results confirms single-phase spinel structure. Scanning electron microscopy (SEM) of the prepared ferrites reveal that vanadium addition resulted in a rapid grain growth with large pores trapped inside the grains as the vanadium concentration increases. The ac conductivity σac has been studied as a function of frequency and temperature over the temperature range (300–600 K). The results obtained for these materials reveal a semiconductor – to semimetal transition as V5+ content increases. All studies composition exhibit a transition with change in the slope of conductivity. The obtained temperature Tc is found to be decrease with the increasing vanadium content. The hopping of electrons between Fe3+ and Fe2+ as well as the hole hopping between Ni3+ and Ni2+ are found to responsible for the conduction mechanism. The relation of the universal exponent s with temperature gives evidence for the presence of the correlation barrier hopping (CHB) mechanism in these compounds. The impedance technique has been used to study effect of grain and grain boundary on the electrical properties. The analysis data show only one semi-circle for all samples except for sample with x = 0.05. The results suggested that the conduction mechanism takes place predominantly through the grain in the studied samples.  相似文献   

18.
Melt-spun Nd13Dy2Fe77−xCoxC6B2 (x=0, 5, 10, 15, 20) ribbons with a high coercivity more than 2 T have been obtained. It was found that the ribbons quenched at the optimum wheel speed 15 m/s (as-spun ribbons) mainly consist of ferromagnetic 2 : 14 : 1 phase and paramagnetic NdC2 phase, and the ribbons spun at 25 m/s and subsequently annealed at 973 K for 15 min (as-annealed ribbons) are primarily composed of the magnetic 2 : 14 : 1 and 2 : 17 phases. The magnetization process of as-spun ribbons controlled by a pinning of the domain wall is different from that of as-annealed ribbons determined by a nucleation of the reverse domain. This significant difference originates possibly from the existence of paramagnetic NdC2 phase acting as a pinning center in as-spun ribbons. In the as-annealed ribbons, the substitution of Co for Fe leads to increase of remanence (μ0Mr), maximum energy product ((BH)max) from 0.67 T, 9.7 MGOe for x=0 to 0.84 T, 14.4 MGOe for x=10, respectively. A coercivity of 2.74 T is obtained for as-quenched Nd13Dy2Fe77−xCoxC6B2 (x=0) ribbons.  相似文献   

19.
Temperature and pressure dependence of magnetic properties in the NdMn2−xFexGe2 series of solid solutions (0.1⩽x⩽1.0) are reported. The (P, T) magnetic phase diagrams are determined on the basis of the AC magnetic susceptibility measured in a weak magnetic field. The measurements were carried out under hydrostatic pressure up to 1.5 GPa in the temperature range 80−430 K. The reported data show that in the studied series of solid solutions, a drastic change in magnetic properties takes place in a narrow dilution parameter range (0.4⩽x⩽0.5). While taking into account the magnetic properties, the studied range of Fe content could be divided into four regions. Only in the case of x=0.3 and 0.4, the external pressure significantly influences the magnetic properties of the samples.  相似文献   

20.
《Solid State Ionics》2006,177(7-8):669-676
The electrical conductivity of sintered samples of Ce1−xNdxO2−x / 2 (0.01  x  0.2) was investigated in air as a function of temperature between 150 and 600 °C using AC impedance spectroscopy. The individual contribution of the bulk and grain boundary conductivities has been discussed in detail. In the low temperature range (< 350 °C), the activation enthalpy for bulk conductivity exhibited a shallow minimum at 3 mol% Nd, with a value of 0.68 eV. The activation enthalpy also produced a shallow minimum at 5 mol% Nd in the high temperature range (> 350 °C), with a value of 0.56 eV. It was shown that Ce1−xNdxO2−x / 2 is an electrolyte that obeys the Meyer Neldel rule. The bulk conductivity data measured by others for the same system has also been recalculated and re-evaluated to facilitate easier comparison with our own data.  相似文献   

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