Materials Literature
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We present a theoretical description of the influence of conduction-electron--local-moment exchange on the properties of free carriers in antiferromagnetic semiconductors, with explicit application to EuTe. We conclude that the ferron, an electron self-trapped in a potential well formed by exchange-induced ferromagnet…
The absolute total electron scattering cross section for methane (inelastic+elastic, integrated over all angles) was measured with a time-of-flight electron transmission spectrometer for incident energies from 1.3 to 50 eV. The major discrepancies that exist between recent absolute measurements of the total cross sect…
A macroscopic model of the microcontacts in ceramic ZnO varistors was prepared by using ZnO single-crystal plates and a layer of the usual oxide additives. The electrical properties of these model contacts are very similar to those of the microcontacts. Measurements on one-sided macrocontacts require the assumption of…
The electron velocity distribution is calculated for an idealized model of the high electron mobility transistor using a many-particle Monte Carlo model and a self-consistent two-dimensional Poisson solver. Hot electron effects, nonstationary effects, and real space transfer are analyzed. The results show that signifi…
We model the phonon spectra of the diamond-structure compounds C, Si, Ge, Sn and the zinc-blende-structure compounds GaP, GaAs, and ZnS. We use a four-parameter valence-force model consisting of first- and second-neighbor forces plus the very important coplanar angle-angle interaction introduced by McMurry et al. Alth…
The results of an experimental study of dc and microwave electrical conductivities, electron-spin resonance, optical reflection, and infrared absorption in ${\mathrm{FeCl}}_{3}$-doped polyparaphenylene (PPP) are presented. In low-conducting PPP, the conductivity is described by interpolaron hopping processes among the…
[ PtC12(C6 H 13N)(CsH 11P)] The shortest intermolecular contact [3.46 (2)A], observed between N and Cl(2)[~+x, ~--y, - z ] , is probably due to an N - H . . . C 1 hydrogen bond. The packing arrangement is shown in Fig. 3. Thanks are due to Dr G. Consiglio (ETH, Zfirich) who kindly prepared the compound. The drawings w…
Theoretical and experimental results describing the dependence of the Seebeck and Peltier coefficients on the composition of Ga1−xAlxAs solid solution are given. The Seebeck coefficient for nondegenerately doped n- and p-type Ga1−xAlxAs is given by the simple expressions αn=(k/e)(lnNc/n+2) and αp=−(k/e)(lnNv/p+2), res…
We have studied the charge-density-wave phase transition of ${\mathrm{TiSe}}_{2}$ using photoelectron spectroscopy with high angle and energy resolution. We accurately measured the band dispersions of the Se 4p and Ti 3d bands, whose interaction is thought to be deeply involved in the phase transition. In contrast to…
Depending on the dopant concentration, two distinct types of porous silicon can be formed during the anodization of silicon in hydrofluoric acid. A range of samples of both types of porous silicon has been investigated using x-ray double crystal diffraction techniques. The crystal lattice of porous silicon is found to…
Crystals of K 3 Fe(CN) 6 undergo a second-order phase transition accompanied by a soft mode at about 130 K. The crystal structures of the room- and low-temperature phases have been determined by X-ray diffraction. Crystals of the room-temperature phase are monoclinic with space group P 2 1 / c , a =7.058(1), b =10.426…
We report an analysis of new and previously existing optical absorption and fluorescence data, far-infrared data, and electronic Raman scattering data for Eu3+, Dy3+, and Er3+ in the C3i sites of Y2O3 and R2O3, where R=a rare earth. Our previous analysis of C2-site spectra yields an effective point-charge model for th…
The emission spectrum of Tb3+ substituted in YAG to various concentrations (x in Y3−xTbxAl5O12 ranges from 3×10−5 to 3×10−1) has been measured on samples prepared by two different methods. These methods are powder preparation by coprecipitation and growth of crystalline layers by liquid-phase epitaxy. The spectrum con…
The previously postulated production of holes during the electrical breakdown of varistors has been directly verified. In some compositions band-gap (3.2 eV) luminescence from the recombination of these holes with free electrons has been observed. The intensity of this luminescence is greater in varistor compositions…
We have performed an extended x-ray-absorption fine-structure (EXAFS) measurement of ${\mathrm{Cd}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$${\mathrm{Mn}}_{\mathrm{x}}$Te solid solutions for various concentrations x in the single-phase range 0\ensuremath{\le}x\ensuremath{\le}0.7. Data have been collected on the Mn K, Cd…
The physical and electronic properties of poly(isothianaphthene) PITN, are reported, including initial characterization, electrochemical cyclic voltammetry, spectroscopy, and transport properties. PITN has the smallest energy gap of any known conjugated organic polymer, Eg≂1 eV. This novel conjugated polymer exhibits…
The light stabilization of polypropylene (PP) fibers places special requirements on the stabilization system due to the high surface to volume ratio, the severe processing conditions, and the post spinning treatments. Earlier systems provided only moderate performance lifetimes thus limiting the markets for PP fibers.…
The properties of hindered diazacycloalkanones were evaluated as light stabilizers and antioxidants for polypropylene. A totally hindered piperazinone was found to be excellent light stabilizer with many other desirable properties as a polymer additive. Partially hindered decahydroquinoxalinone derivatives were found…
Since their initial production by our laboratories about ten years ago, hindered amine light stabilizers (HALS) have become established as excellent light stabilizers of polymers. This review deals with their synthesis, evaluation and development.
Although polyethylene is essentially nonbiodegradable, it was found that copolymers of ethylene and 2-methylene-1,3-dioxepane prepared by a high pressure free radical solution polymerization were indeed biodegradable. Most synthetic polymers are not biodegradable because they have not been on the earth long enough to…