Materials Literature
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New upconversion phosphor BaCl2 containing 28 mol% Er3+ exhibited extremely bright green luminescence, and the fluorescence intensity of the chloride at 550 nm and under 1.516 μm (5mW) laser diode excitation was 40 times greater than that of conventional Er3+-doped fluoride. The excitation spectrum and stability of th…
Quasi-static stress relaxation and dynamic internal friction measurements of stress induced reversible structural relaxation were performed on the amorphous alloy Fe40Ni40B20. The kinetics can be well described by a stretched exponential Kohlrausch-Williams-Watts quasi-static relaxation. The thermally activated part o…
The luminescence spectra of Y2TiO5 and Y2Ti2O7, NaSn2−xTix(PO4)3 and Y3Ga5O12:Ca,Ti are reported. The titanate host lattices are also doped with Eu3+. The data are discussed in terms of existing models. It is shown that a relation between quenching temperature and excitation maximum of the titanate emission holds and…
(Bi0.5Sb0.5)2Te3 single crystals doped with In atoms (cIn = 0 to 9.8 × 1020 cm−3) are prepared by the modified Bridgman method. From the analysis of the measurements of reflection spectra in the plasma resonance-frequency region, electrical conductivity, and the Seebeck coefficient it is found that an increase in the…
Several possibilities to design a cheap red lamp phosphor are reviewed. It appears to be possible to increase the amount of energy transfer from the niobate group in CaNb2O6 to Eu3+ on calcium sites by suitable substitutions. However, part of the niobate excitation energy still does not reach the Eu3+ ion. Only the me…
Numerical calculations of the density of tunneling and vibrational states of glasses within the soft-potential model (an extension of the tunneling model to include soft vibrations) are reported and compared to analytical approximations. Using a specific assumption on the asymmetry of the soft potentials, one is able…
A three-dimensional simulation of dislocation dynamics and interactions is applied to the question of the formation of cell structures in single crystals oriented for multiple slip. The numerical conditions selected are those of a [100]-oriented aluminium single crystal tested in constant total strain rate with a high…
For pt.II see ibid., vol.5, p.945 (1993). Measurements of the linear optical birefringence were used to determine the phase diagram of TbPO 4 at temperatures down to 1.4 K. At least one new structural and magnetic phase transition was found that is not detectable in magnetic investigations. Calculations using an appro…
Diaquabis(oxoacetato-O,O'')germanium(IV), [Ge(C 2 H 2 O 3 ) 2 (H 2 O) 2 ], was prepared from germanium dioxide and glycolic acid in refluxed H 2 Oand identified with IR, 1 H NMR, 13 C NMR, mass spectrum, elemental analysis, and X-ray single crystal structure determination. C 4 H 8 GeO 8 , M r =256.7, monoclinic, P2 1…
In situ Si-TaSi2 composites are studied by synchrotron white beam topography and by double axis diffractometry. These results show that the single crystal Si matrix is of excellent quality: Rocking curve widths are between 40 and 60 s of arc, and the topographs do not exhibit asterism. Diffuse radial streaks in the La…
The scaling relations close to the ideal glass transition point in a self-consistent mode coupling model with realistic structural properties are studied. The behavior of the long time limit of the density autocorrelation function or the nonergodicity parameter over a reasonable density range around the transition poi…
Luminescence spectroscopy of nanocrystals (100 nm) has been used to probe the details of the low-temperature photophysics of AgBr, an indirect-gap semiconductor. Small crystallite size, moderate excitation levels, and radiative decay rates create a situation in which only one electron-hole pair exists in a given nanoc…
Abstract In this paper I review the evidence that shows that the optical and electronic properties of semiconducting diamond can be understood in terms of boron acceptors partially compensated by deep donors. In natural semiconducting diamond, in which the total impurity concentration is less than 1 ppm, there is a lo…
Later-stage spinoidal decomposition (SD) of off-critical mixtures of poly(styrene-ran-butadiene) SBR/polyisoprene or SBR/polybutadiene was investigated by time-resolved light scattering. Changes in the scaled structure factor F(x,t)≡qm(t)3I(x,t) with x≡q/qm(t) were determined as a function of the composition w of the…
The \ensuremath{\pi}-electronic structural changes in a polyene molecule containing seven double bonds, \ensuremath{\alpha},\ensuremath{\omega}-diphenyltetradecaheptaene (DP7), have been studied upon gradually doping with sodium, using x-ray and ultraviolet photoelectron spectroscopies. The spectra are interpreted wit…
We have studied phonon states of Ge small particles by Raman scattering resonating with the ${\mathit{E}}_{1}$\ensuremath{\sim}${\mathit{E}}_{1}$+${\mathrm{\ensuremath{\Delta}}}_{1}$ gaps. Those particles are prepared by evaporation in Ar gas atmosphere and their sizes range from about 2 through 30 nm. Since the elect…
Total electron and total and partial ion yield spectra of Ar clusters (with average size up to 600±200) in the region of Ar 2p excitation have been measured using synchrotron radiation and time-of-flight mass spectrometry. As the average cluster size increases, the x-ray absorption spectrum changes systematically from…
We investigate the optical excitation of visible room-temperature luminescence in electrochemically produced porous silicon and in siloxene obtained from the chemical reaction of calcium disilicide with hydrochloric acid. Luminescence and luminescence excitation spectra (2--5 eV) of different porous silicon and siloxe…
The propagation of acoustic waves in superlattices is investigated within the effective-medium model generalized to the quasiperiodic structure. The effective elastic constants are analytically obtained in closed form for superlattices with hexagonal symmetry. These results are used to interpret the observed low-frequ…
We prepared silica glasses having various concentrations of chlorine, fluorine, hydrogen (SiO2−x), and oxygen (SiO2+x) to examine the precursors of paramagnetic centers induced by γ rays. In the case of glasses sintered under chlorine and hydrogen ambients, the concentration of the E′ center induced by γ-ray irradiati…