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91.
Iron redox equilibrium, structure and properties were investigated for the 10ZnO-30Fe2O3-60P2O5 (mol%) glasses melted at different temperatures. The structure and valence states of the iron ions in these glasses were investigated using Mössbauer spectroscopy, Raman spectroscopy and differential thermal analysis. Mössbauer spectroscopy indicated that the concentration of Fe2+ ions increased in the 10ZnO-30Fe2O3-60P2O5 (mol%) glass with increasing melting temperature. The Fe2+/(Fe2+ + Fe3+) ratio increased from 0.18 to 0.38 as the melting temperature increased from 1100 to 1300 °C. The measured isomer shifts showed that both Fe2+ and Fe3+ ions are in octahedral coordination. It was shown that the dc conductivity strongly depended on Fe2+/(Fe2+ + Fe3+) ratio in glasses. The dc conductivity increases with the increasing Fe2+ ion content in these glasses. The conductivity arises from the polaron hopping between Fe2+ and Fe3+ ions which suggests that the conduction is electronic in nature in zinc iron phosphate glasses. 相似文献
92.
Nano-meter sized structural inhomogeneities of (CuI)0.52-(Cu2MoO4)0.48 superionic conducting glass were investigated by high resolution transmission electron microscopy. The as-quenched sample of CuI-Cu2MoO4 is a homogeneous glass, in which the CuI component is finely and uniformly dispersed among the oxyanions of Cu2MoO4 glassy matrix. A two-step crystallization, starting at 440 and 495 K, was observed in the glass. After the first step crystallization, precipitating nano-crystalline cubic CuI 2-3 nm in diameter, the electrical conductivity increases by about 50%. On the other hand, the electrical conductivity decreases with the second crystallization event forming crystalline phases of CuI, Cu2O and others 20-30 nm in diameter. 相似文献
93.
A. Tölle H. Zimmermann F. Fujara W. Petry W. Schmidt H. Schober J. Wuttke 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,16(1):73-80
Low-frequency vibrations of glassy and crystalline orthoterphenyl are studied by means of neutron scattering. Phonon dispersions
are measured along the main axes of a single crystal, and the corresponding longitudinal and transversal sound velocities
are obtained. For glassy and polycrystalline samples, a density of vibrational states is determined and cross-checked against
other dynamic observables. In the crystal, low-lying zone-boundary modes lead to an excess over the Debye density of states.
In the glass, the boson peak is located at even lower frequencies. With increasing temperature, both glass and crystal show
anharmonicity.
Received 7 December 1999 相似文献
94.
R.M.C. de Almeida N. Lemke I.A. Campbell 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(3):513-518
We study random walks on the dilute hypercube using an exact enumeration Master equation technique, which is much more efficient
than Monte Carlo methods for this problem. For each dilution p the form of the relaxation of the memory function q(t) can be accurately parametrized by a stretched exponential over several orders of magnitude in q(t). As the critical dilution for percolation is approached, the time constant tends to diverge and the stretching exponent drops towards 1/3. As the same pattern of relaxation is observed in a wide class of glass formers, the fractal like morphology
of the giant cluster in the dilute hypercube appears to be a good representation of the coarse grained phase space in these
systems. For these glass formers the glass transition may be pictured as a percolation transition in phase space.
Received 16 June 2000 and Received in final form 13 October 2000 相似文献
95.
D.A. Tenne V.A. Haisler N.T. Moshegov A.I. Toropov A.P. Shebanin D.R.T. Zahn 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,8(3):371-376
We present the forward Raman scattering study of zone-centre optical phonon anisotropy in short-period GaAs/AlAs superlattices.
Experiments were performed on specially prepared superlattice structures having anti-reflection dielectric coatings and removed
substrates. The experimental data are compared with the angular dispersion of superlattice optical phonons calculated within
the dielectric susceptibility model. We have found a good agreement between the experimental data and the calculations taking
into account interface disorder.
Received 9 September 1998 and Received in final form 22 October 1998 相似文献
96.
O.J. Zogal A.H. Vuorimäki E.E. Ylinen 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,10(2):201-207
2H NMR spectra and spin-lattice relaxation rates, R1 are measured as functions of temperature (4.2-310 K) for YD1.99 and YD1.99+0.04. In YD1.99 the measured temperature dependence of R1 is explained by the interaction of deuteron spins with conduction electrons and the value s-1 K-1 is obtained for the inverse Korringa product . Most of the spectral features in the “rigid” lattice regime are described by the dipolar interaction. No evidence of the
deuterium self-diffusion was observed in the measured temperature range. The low-temperature spectra in YD1.99+0.04 consisted of two components: a central line and a doublet characteristic for the quadrupole interaction. The central line
corresponds to zero electric field gradients (EFG) at the sites of the deuterons which have a surrounding with cubic symmetry
like in YD1.99. The doublet indicates a non-zero EFG which can be explained in terms of the presence of short-range ordered domains of the
hypothetical YD2.25 stoichiometry. Other possible interpretations of the spectra are also discussed. In the vicinity of 250 K both spectra and
R1 reflect the onset of the rapid motion of deuterium atoms. The linear dependence of R1 at low temperatures yields s-1 K-1.
Received 8 September 1998 相似文献
97.
The amorphous networks Si3B3N7 and ‘SiBN3C' are studied by solid-state nuclear magnetic resonance (NMR), continuous-wave and pulse electron paramagnetic resonance (EPR), and by one- and two-dimensional electron nuclear double resonance spectroscopy. In both compounds, boron is found to be coordinated exclusively by nitrogen with close to trigonal planar geometry and close to equal bond lengths. Silicon is four-coordinated by nitrogen with the coordination tetrahedra being distorted to accommodate the coordination preferences of boron. REDOR measurements demonstrate that boron resides in the second coordination sphere of silicon. Carbon incorporation into the Si–B–N network does not lead to any observable changes in NMR parameters including the average dipolar coupling between 11B nuclei which depends on the average distance of the boron atoms. Only spin–lattice relaxation of the nuclei is accelerated due to the generation of paramagnetic centers. The unpaired electrons appear to be delocalized over several carbon atoms and exhibit significant hyperfine couplings to boron, silicon, nitrogen, and some residual protons. In contrast to electron spectroscopic imaging experiments, the magnetic resonance results suggest formation of carbon clusters. 相似文献
98.
A new transparent conducting oxide (TCO) film with low resistivity and high transmittance in the visible range, molybdenum-doped zinc oxide (MZO), was successfully prepared by RF magnetron sputtering method on glass substrates at room temperature. The structural, electrical, and optical properties as a function of film thickness were investigated. All the samples have a preferred orientation with the (0 0 2) planes parallel to the substrates. The resistivity initially decreases and then shows an increase with the increase of the film thickness. When the thickness is 400 nm, the film has its best crystallinity and lowest resistivity 9.2 × 10−4 Ω cm with a Hall mobility of 30 cm2 V−1 s−1 and a carrier concentration of 2.3 × 1020 cm−3. The average transmittance in the visible range exceeds 84% for all thickness films. 相似文献
99.
L. Bellon M. Gibert R. Hernández 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,55(1):101-107
We study thermal convection in a colloidal glass of Laponite in formation. Low concentration preparation are submitted to
destabilizing vertical temperature gradient, and present a gradual transition from a turbulent convective state to a steady
conductive state as their viscosity increases. The time spent under convection is found to depend strongly on sample concentration,
decreasing exponentially with mass fraction of colloidal particles. Moreover, at fixed concentration, it also depends slightly
on the pattern selected by the Rayleigh Bénard instability: more rolls maintain the convection state longer. This behavior
can be interpreted with recent theoretical approaches of soft glassy material rheology. 相似文献
100.
J. Mahoney V. Tarnovsky K. H. Becker 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(2):289-293
We measured absolute partial cross sections for the formation of all singly
charged positive ions produced by electron impact on SiCl2 and SiCl
from threshold to 200 eV using the fast-neutral-beam technique. Some of the
cross section curves exhibit an unusual energy dependence with a pronounced
low-energy maximum at an energy around 30 eV, which may be indicative of the
presence of indirect ionization channels. Dissociative ionization channels
are dominant for both species. The experimentally determined total single
ionization cross sections for both species agree very well with calculated
cross sections using the Deutsch-M?rk (DM) formalism. A brief summary of
the ionization cross sections determined for all four SiClx (x=1–4)
species is given highlighting similarities and differences. 相似文献