Materials Literature
按标题、摘要、年份、主题和来源检索公开元数据。结果保留作者、摘要、分类与原始来源链接。
The authors present a comparative study of the properties of two solution-processible alkyl-substituted polythienylenes, poly(3-hexyl thienylene), P3HT and poly(3-dodecyl thienylene), P3DT. Both show the onset of pi - pi * interband absorption at 2 eV with the peak in absorption coefficient near 2.5 eV, and both show…
The first measurements are reported for the AC conductivity (real and imaginary parts) of the semiconducting CuO-Bi 2 O 3 -P 2 O 5 glasses in the frequency range 10 2 -10 5 Hz and in the temperature range 80-4000 K. The experimental results have been analysed in the light of various theoretical models proposed for amo…
The structures of 2H PbI 2 , grown from a gel, and of 4H PbI 2 , obtained by thermal transformation of 2H at 423 K, have been determined by single-crystal X-ray analysis. The space groups are P3m1 for 2H and P3m1 for 4H. The occupancy of the atomic sites in the 2H and 4H structures is only about 80-85%, indicated by a…
Photoluminescence and cathodoluminescence are studied in MgO and CaO stabilized ZrO2 crystals before and after mechanical damage by grinding and Vickers indentations. Significative differences in the emission and excitation spectra are found between crystals stabilized by MgO and CaO. Mechanical damage in cubic stabil…
The hardness of materials, H, is dependent on grain diameter, d, in a similar way as the flow stress in the Hall-Petch relation: H = Ho + KHd−1/2, where, Ho and KH are constants. The microhardness of 2S-Al (99.5% Al), pure Cu, Al-MD 105 (Al-1% Al2O3), and Duralumin (Al-3.94% Cu) is found to vary with grain size accord…
For KH 2 PO 4 (KDP) and NH 4 H 2 PO 4 (ADP), the orientation of the optical indicatrix for NaD light (589 nm) has been determined in the low temperature orthorhombic phase, through the optical and X-ray measurements. For both KDP and ADP, the principal refractive indices, n a , n b and n c have been found to satisfy n…
[YC12(H20)6]C1, Mr = 303.356, monoclinic, P2/n, a = 7.8346 (25), b = 6.4729 (26), c = 9.5817 (50) angstroms, beta = 93.768 (35) °, V = 484.86 cubic angstroms, Z = 2, Dx = 2.0776 g cm -3, Mo Kalpha (A = 0.71069 angstroms),/z = 68.66 cm- 1, F(000) = 300, room temperature, final R = 0.0449 for 940 unique observed reflexi…
The spatial and temporal evolution of photodarkening in chalcogenide glasses is simulated by a simple kinetic model and tested against experiments. In the model, photodarkening, a gradual decrease of the energy of the absorption edge caused by above-band-gap illumination, is the additional absorption at defects create…
The anions of (TMTSF) 2 ClO 4 order below about 24 K. The speed at which this transition is passed has a drastic influence on the low temperature electronic properties of this salt. We determined as a function of the cooling rate the number of ordered ClO 4 as well as the average size of the ordered domains. A high re…
The phase transition sequence of a K 2 ZnBr 4 crystal was investigated by DTA and dielectric measurements. It was found that the crystal undergoes at least two phase transitions, at -118°C and around 200°C, on heating. Ferroelectricity was observed below the lower transition point.
We report a first-principles, local-density-functional (LDA) calculation of the electronic structure of crystalline, three-dimensional (3D) trans-(CH${)}_{\mathit{x}}$. For the perfect crystal, we find a broken-symmetry ground state having P${2}_{1}$/a space-group symmetry, corresponding to in-phase dimerization on ne…
In the present work we make M\"ossbauer and magnetization studies of the ${\mathrm{Ti}}^{4+}$-substitution effect in the ${\mathrm{Ni}}_{1\mathrm{\ensuremath{-}}\mathit{y}}$${\mathrm{Zn}}_{\mathit{y}}$${\mathrm{Fe}}_{2}$${\mathrm{O}}_{4}$ ferrite (y=0.3 and 0.4). In this range the M\"ossbauer spectra are not relaxed a…
Hydration phase transitions in Na vermiculite, a specific example of expandable 2:1 layered silicates, were examined as a function of temperature at a constant water-vapor pressure by x-ray diffraction. The samples exhibited well-defined 0-, 1-, and 2-water-layer hydration states (WLHS's) with the basal spacings of 9.…
We report on the molecular-beam-epitaxy growth of CdS films on CdTe(110), studied with reflection high-energy electron diffraction (RHEED) and angle-resolved photoemission spectroscopy. The exponential attenuation of the Te 4d core-level emission as a function of the CdS film thickness and the persistency of the subst…
The influence of surface roughness on the electrical conductivity of polycrystalline metal films has to be considered at two different length scales. The large-scale surface roughness due to the granular arrangement of these films gives rise to a fluctuating film cross section. One-dimensional models of these fluctuat…
A simple but tractable model of the density of exciton states associated with potential fluctuations in semiconductor alloys is proposed. It consists of minimizing the fluctuation entropy related to the composition fluctuation \ensuremath{\Delta}x averaged over a volume V, for a given localization energy \ensuremath{\…
Photoelectron diffraction has been measured from a (001) single-crystal surface of aluminum. Anisotropies of the photocurrent of 73% and 65% have been observed in azimuthal scans of 2s and 1s core-level intensities comprising the [011] direction. Azimuthal intensity scans have also been measured for the plasmon-loss p…
Polarized, depolarized, isotropic, difference, and reduced Raman spectra were obtained from vitreous silica, irreversibly compacted at 600 °C and 50 kbar, to ambient densities as high as 2.73 g cm−3. The 60 cm−1 ‘‘Boson’’ peak; and, the intense optic, Si–O–Si bending peak at 440 cm−1 including its low-frequency should…
The weak-localization phenomenon for two-dimensional (2D) electronic systems is invoked to explain the negative magnetoresistance as well as the low-temperature dependence of the resistivity of pyrocarbon samples heat treated between 2000 and 2600 \ifmmode^\circ\else\textdegree\fi{}C. The 2D character is found to orig…
Optical absorption over a large dynamic range obtained by two different experimental techniques is reported for an undoped α-Al2 O3 single crystal. Absorption data are presented in two energy ranges: 0.94–3.5 eV and 4.5–8.6 eV. Vacuum ultraviolet (vuv) absorption measurements were performed on three boules of Czochral…