共查询到20条相似文献,搜索用时 15 毫秒
1.
Korovushkin V. V. Trukhanov A. V. Kostishin V. G. Isaev I. M. Shchetinin I. V. Durov N. M. Mironovich A. Yu. Minkova I. O. Astapovich K. A. 《Physics of the Solid State》2020,62(5):891-901
Physics of the Solid State - The features of the composition, crystal, and magnetic structure of Ti-substituted barium hexaferrite BaFe12 – xTixO19 (0.25 ≤ x ≤... 相似文献
2.
《Superlattices and Microstructures》1997,21(3):459-461
A series of superconducting cuprates with the nominal composition YBa2Cu3 − xCdxO7 − yand the effect of Cd substitution on Cu sites in this compound is presented. X-ray powder diffraction patterns for these cadmium cuprates with reduced diamagnetism indicate an orthorhombic unit cell like-perovskite structure for (0 ≤ x ≤ 0.15), while for higher Cd concentration, i.e.x = 1.0 the material is polyphasic. The observed superconducting transition temperature of the samples is nearly the same ([formula] K), except for (x = 1.0) whereTcdrops to 72 K and a transition from metallic to semiconducting behavior of the normal state of the resistivity is observed. Such a decrease inTcfor higher Cd concentration could be attributed to the presence of the green phase in this composition. 相似文献
3.
《Superlattices and Microstructures》2001,30(2):75-80
In this work, the electronic structure and disorder effects in copper halides alloys are studied by means of the full potential linearized augmented plane wave (FLAPW) method. The calculated bowing parameter shows that the main contribution is due to the relaxation effects, though the charge transfer remains relatively significant, while the volume deformation contribution is negligible. The total bowing is found to be small in the three studied alloys. Results agree well with experimental and available theoretical works. 相似文献
4.
《Superlattices and Microstructures》2001,30(1):9-19
In order to clarify the electronic and optical properties of wide-energy gap zinc-blende structures ZnSe, MgSe and their alloys (ZnSe)1 − x(MgSe)x, a simple pseudo-potential scheme (EPM) within an effective potential, the virtual crystal approximation (VCA) which incorporates compositional disorder as an effective potential, is presented. Various quantities, including the fundamental band gap, the energies of several optical gaps, charge densities, ionicity character, transverse effective charge, and refractive index are obtained for this alloy. 相似文献
5.
《Superlattices and Microstructures》2001,30(5):241-251
The electronic, optical and elastic properties of the ternary II–VI semiconductor alloys Cd1 − x Zn xTe are calculated by thesp3s * semi-empirical tight-binding theory and the bond-orbital model. We found a nonlinear decrease of the transverse effective charge and refractive index and a nonlinear increase of the bandgap and elastic constants with increasing Zn composition x. For all these behaviours, the corresponding bowing factors are predicted. The results are compared with previous theoretical estimates and experiments. 相似文献
6.
Anikin M. S. Tarasov E. N. Neznakhin D. S. Semkin M. A. Selezneva N. V. Andreev S. V. Ragozina M. V. Zinin A. V. 《Physics of the Solid State》2022,64(4):222-227
Physics of the Solid State - Crystal structure, temperature and field dependences of magnetization, high-field susceptibility, and magnetocaloric effect (MCE) of... 相似文献
7.
Co-doping B-site of perovskite oxide LaxSr1 ? xCoyFe1 ? yO3 ? δ (LSCFO) with Cr6+ and Mg2+ ions has been attempted in this research for revamping chemical stability and oxygen ionic conductivity of this mixed conducting oxide. It is known that partial substitution for B-site cations of LSCFO by Cr gives rise to a significant improvement on chemical and thermal stability of the perovskite oxide. On the basis of this doped structure, introduction of an immaterial dose of Mg2+ ion into its B-site results in a microstructure consisting of smaller grains with higher density than its precursor. Furthermore, the resulting perovskite oxide La0.19Sr0.8Fe0.69Co0.1Cr0.2 Mg0.01O3 ? δ (LSFCCMO) displays higher O2? conductivity than the solely Cr-doped LSCFO besides the improved chemical stability against reduction in 5% CH4/He stream at 850 °C. A detailed examination of the oxidation states of B-site transition metal ions by XPS has also been conducted as a part of structural characterizations of LSFCCMO. The assessment of relative O2? conductivity shows that the grain boundary area plays a more important role than the bulk phase in facilitating ion transport, but with comparable boundary areas the higher densification level is favorable. 相似文献
8.
The perovskite BaCe(0.9 ? x)ZrxY0.1O(3 ? δ) has been prepared by solid state reaction at 1400 °C and conventional sintering at 1700 °C. Water uptake experiments performed between 400 and 600 °C, at a water vapour pressure of 0.02 atm, provide data on the concentration of protons incorporated in the sample. The direct current conductivity has been measured as a function of oxygen partial pressure, at a water vapour partial pressure of 0.015 atm. The total conductivity has been resolved into a p-type and an ionic component using a fitting procedure appropriate to the assumed defect model. An estimation of the protonic component was made by assuming a conductivity isotope effect between 1.4 and 1.8. The total conductivity, obtained using impedance spectroscopy has been measured as a function of temperature in the water and heavy water exchanged states. The activation energy has been found to be 0.56 eV to 0.59 eV in the water exchanged state with values 0.03 to 0.04 eV higher in the heavy water exchanged state. Impedance spectra measured at 200 °C showed a reduction in grain boundary resistivity with increasing cerium content. The stability of the compounds to carbon dioxide has been studied by thermogravimetry. 相似文献
9.
Pavlukhina O. O. Sokolovskiy V. V. Buchelnikov V. D. Zagrebin M. A. 《Physics of the Solid State》2020,62(6):963-967
Physics of the Solid State - The structure and magnetic properties of FeRh1 – xIrx alloys (x = 0.5, 0.625, 0.75, 0.875, and 1) are investigated by first-principles methods... 相似文献
10.
Akira Yoshiasa Osamu Ohtaka Daisuke Sakamoto Denis Andrault Hiroshi Fukui Maki Okube 《Solid State Ionics》2009,180(6-8):501-505
(Mg1 ? xFex)1 ? δO (x = 0.01–0.43) single crystals (~ 8 mm in diameter) were made by a melt-growth method. Electrical conductivity measurements were carried out as functions of temperature and frequency by a complex impedance method under pressure (~ 43 GPa and ~ 673 K and at 0.1 MPa and ~ 1400 K). Our experimental results show a change in charge transport mechanism in the (Mg1 ? xFex)1 ? δO solid solution at high temperature. The temperature of inflection point of the slope in Arrhenius plots depend greatly on both composition and extrinsic factors of crystals. The low-temperature conduction mechanism in (Mg1 ? xFex)1 ? δO solid solution is small polaron. Pressure effect of the electric conductivity was observed and the conductivity increased to 0.5 at log scale of S/m with increasing pressure up to 43.4 GPa. The activation energy was decreased linearly with increasing pressure. Chemical composition and homogeneity of specimen rather than pressure greatly influence the electric conductivity. The activation energy of 2.37(4) eV for the (Mg0.99Fe0.01)1 ? δO solid solution might correspond to a migration enthalpy of O ions through thermally formed defects. It is proposed that a possible dominant electrical conduction mechanism in ferropericlase under the lower mantle conditions, at least in the higher temperature region, is super ionic conduction. 相似文献
11.
《Superlattices and Microstructures》1998,23(2):453-465
In order to clarify the electronic properties of the ternary compound semiconductor GaPN, in a zinc-blende structure, a simple pseudopotential scheme (EPM), within an effective potential (VCA), is proposed. The effects of disorder and spin–orbit coupling are neglected. Various quantities, such as energy levels, charge densities, ionicity character, transverse effective charge, and refractive index are obtained for this alloy. Moreover, the crossover of the direct and indirect band gaps is predicted. 相似文献
12.
The europium dopant concentration in strontium cerate was studied to achieve maximum hydrogen permeation. In order to determine high ambipolar conductivity, total conductivity and open circuit potential measurements were performed. Among the three different compositions of Eu-doped SrCe1 ? xEuxO3 ? δ (x = 0.1, 0.15 and 0.2) studied, SrCe0.9Eu0.1O3 ? δ showed highest total conductivity between 600 °C and 900 °C. However, transference number measurements showed increasing electronic conductivity with increasing dopant concentration and a stronger temperature dependence for electronic conduction. Therefore, the highest ambipolar conductivity was obtained over the compositional range from SrCe0.85Eu0.15O3 ? δ to SrCe0.8Eu0.2O3 ? δ depending on temperature. Finally, the hydrogen permeation flux was calculated based on the ambipolar conductivity and compared with experimental results. 相似文献
13.
《Journal of magnetism and magnetic materials》1987,69(3):317-324
The cationic distributions, ionic valencies and magnetic structures of the magnetoplumbite-like BaFe12-xMnxO19 hexagonal ferrites have been studied from powder diffraction data in the paramagnetic and ferrimagnetic phases. The paramagnetic diagrams show that the Mn cations enter all the sublattices of the M-type structure except the pseudo-tetrahedral one within the R-block. It is also concluded that, in the spinel block, the tetrahedral site is occupied by Fe3+ and Mn2+ ions whereas in the remaining octahedral sites are located Fe3+, Mn3+, Mn4+ cations in a selective way and with a hierarchy of preferences. From the magnetic diagrams it is concluded that even if the long range magnetic ordering has a collinear ferrimagnetic character, the 12k and 2a octahedral sublattices present a random moment canting which decreases further the saturation magnetization. 相似文献
14.
A combination of infrared spectroscopy, X-ray photoelectron spectroscopy and density functional theory has been used to investigate the adsorption behavior of glycine at the Ge(100) ? 2 × 1 surface under ultrahigh vacuum conditions. Comparison of experimental and simulated IR spectra indicates that at 310 K, glycine adsorbs on Ge(100) ? 2 × 1 via O–H dissociation, with some fraction of the products also forming an N dative bond to a neighboring germanium atom. O–Ge dative bonding is not observed. As coverage increases, the surface concentration of the monodentate O–H dissociated adduct increases, while that of the N dative-bonded species appears constant. XPS data support and clarify the IR findings and reveal new insights, including the presence at higher coverage of a minor product that has undergone dual O–H and N–H dissociation. These findings are supported by the calculated energy diagrams, which indicate that the reaction of a glycine molecule on the Ge(100) ? 2 × 1 surface via O–H dissociation and interdimer N dative bonding is both kinetically and thermodynamically favorable and that N–H dissociation of this adduct is feasible at room temperature given incomplete thermal accommodation along the reaction pathway. 相似文献
15.
The carbides of NdDy0.2Fe12-yMoyC0.6 (y = 1.5, 2) crystallized in the ThMn12-type structure have been successfully synthesized by arc melting method, followed by a heat treatment. The magnetic properties are strongly enhanced with the addition of carbon. Upon the carbonation the saturation magnetization Ms is increased by about 20emu/g and the Curie temperature Tc is enhanced by 40-70K. The spin reorientation (SR) temperature decreases from 125 K for NdDy0.2Fe10Mo2 to 55 K for NdDy0.2Fe10MO2C0.6 indicating the change of magnetocrystalline anisotropy in the Nd sublattice. It is found that the intrinsic magnetic properties of the carbides can be improved by further nitrogenation, The composite carbon-nitrogen compounds show a Tc - 560K, M8 - 105 emu/g and Ha (anisotropy field) - 86kOe for NdDy0.2Fe10Mo2Co.6Nz and a Tc- 628K, M8 - 119 emu/g and Ha - 115kOe for NdDy0.2Fe10.5Mo1.5C0.6Nz. These magnetic properties are even better than those of simple nitrides, suggesting that these compounds can be considered as a good candidate for permanent magnet applications. 相似文献
16.
The influence of adsorbed S on surface segregation in CuxPd1 ? x alloys (S/CuxPd1 ? x) was characterized over a wide range of bulk alloy compositions (x = 0.05 to 0.95) using high-throughput Composition Spread Alloy Film (CSAF) sample libraries. Top-surface and near-surface compositions of the CSAFs were measured as functions of bulk Cu composition, x, and temperature using spatially resolved low energy ion scattering spectroscopy (LEISS) and X-ray photoemission spectroscopy (XPS). Preferential segregation of Cu to the top-surface of the S/CuxPd1 ? x CSAF was observed at all bulk compositions, x, but the extent of Cu segregation to the S/CuxPd1 ? x surface was lower than the Cu segregation to the surface of a clean CuxPd1 ? x CSAF, clear evidence of an S-induced “segregation reversal.” The Langmuir–McLean formulation of the Gibbs isotherm was used to estimate the enthalpy and entropy of Cu segregation to the top-surface, ΔHseg(x) and ΔSseg(x), at saturation sulfur coverages. While Cu segregation to the top-surface of the clean CuxPd1 ? x is exothermic (ΔHseg < 0) for all bulk Cu compositions, it is endothermic (ΔHseg > 0) for S/CuxPd1 ? x. Segregation to the S/CuxPd1 ? x surface is driven by entropy. Changes in segregation patterns that occur upon adsorption of S onto CuxPd1 ? x appear to be related to formation of energetically favored PdS bonds at the surface, which counterbalance the enthalpic driving forces for Cu segregation to the clean surface. 相似文献
17.
《Superlattices and Microstructures》2001,29(2):169-186
We present a review of published work concerning the effect of In and N compositions on the operation wavelength, optical quality and lasing threshold in GaxIn1 − xAs1 − yNy/GaAs QW and double heterostructure lasers. We show that the emission wavelength in the range between 1.0 and 1.4 μ m can be obtained for a wide range of In and/or N concentrations. However, in most Fabry–Perot lasers and vertical cavity surface emitting lasers (VCSELs) reported in the literature, the threshold current density plotted as a function of the relative In/N composition (R = (1 − x) / y) indicate a broad minima for 40 < R < 70, suggesting an optimum relative composition. We also present the results of our studies concerning the optical quality of GaxIn1 − xAs1 − yNy/GaAs single quantum wells for R = 15. We show that the optical quality of GaInAsN can be improved while achieving a red shift in the PL spectra. This is unlike the results obtained by rapid thermal annealing or conventional annealing, which are widely employed as post-growth treatment techniques, where any increase in the PL intensity is almost always accompanied by an undesired blue shift. 相似文献
18.
Shut V. N. Syrtsov S. R. Trublovsky V. L. Petrovic M. Vijatovic 《Physics of the Solid State》2019,61(10):1746-1751
Physics of the Solid State - Samples of homogeneous (x = 0, 0.1, and 0.2) and multilayer ceramics based on solid solutions of nickel–zinc ferrites (Ni1 – xZnx)Fe2O4... 相似文献
19.
We report a systematic study of the layered lithium nitridocuprates Li3 ? xCuxN with 0.1 ≤ x ≤ 0.39. The structural data obtained from experimental XRD patterns, Rietveld refinements and unit cell parameters calculation vs x, indicate that copper (I) substitute interlayer lithium ions in the parent nitride Li3N to form the Li3 ? xCuxN compound without any Li vacancy in the Li2N? layer. Electrochemical results report Li insertion into the corresponding layered structures cannot take place in the 1.2/0.02 V voltage range as in the case of lithium into nitridonickelates and nitridocobaltates. However, in the initial charge process of Li3 ? xCuxN at 1.4 V leading to a specific capacity higher than 1000 mA h/g, the oxidation of copper and nitride ions is probably involved inducing a strong structural disordering process. As a consequence a new rechargeable electrochemical system characterized by discharge–charge potential of ≈ 0.3 V/1.2 V appears from the second cycle. Cycling experiments 0.02 V voltage/0.02 V range induce a complete destruction of the layered host lattice and the presence of Cu3N in the charge state suggests a conversion reaction. The capacity recovered in the 1.4/0.02 V range practically stabilizes around 500 mA h/g after 20 cycles. 相似文献
20.
Motivated by the need to form 1D-nanostructured dopants on silicon surfaces, we have attempted to grow Ga on the high index Si(5 5 12) surface which has a highly trenched (1D) morphology. The evolution of the interface with Ga adsorption in the monolayer regime has been probed by in situ AES, LEED and EELS. Controlling the kinetics by changing the Ga flux rates shows an interesting difference in the 1.0 to 1.5 ML region. The low flux rate (0.03 ML/minute) results in a Frank van der Merwe (layer by layer) growth mode up to 2 ML, while the higher flux rate (0.1 ML/minute) shows a transient island formation after the completion of 1 ML. The low rate shows the formation of 2 × (3 3 7) and (2 2 5) superstructures, while only the 2 × (3 3 7) is observed in a wide coverage range for the higher rate. The results demonstrate the ability to kinetically control the surface phases with different electronic properties of this technologically important interface. 相似文献