Materials Literature
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The crystal structure if RbH 2 PO 4 has been determined by neutron diffraction at room temperature and T c +5K in the tetragonal (paraelectric) phase using single-crystal samples. The techniques of constrained refinement and statistical testing have been used to examine carefully the significance of some pertinent str…
SnO 2 single crystals have been grown by use of vapour-phase reaction method. The crystals obtained are characterised by chemical analysis and electrical measurements. The density of the crystals was determined as 6.994+or-0.001 g cm -3 . The thermal conductivity measured is discussed for different orientations of the…
It is shown that the crystal structures of the binary IV-VI compounds can be classified by parameters derived from a Pauli-force model potential, which has previously been used successfully for the octet and suboctet materials (A N B P-N with P=8 and 2<or=P<or=6). Trends in the transverse effective charges, in the hea…
Synthesis of optically active natural carotenoids and structurally related compounds. IV. Synthesis of (3 R , 3′ R , 6′ R )‐lutein The synthesis of (3 R , 3′ R , 6′ R )‐lutein ( 19 ) according to the building principle C 25 +C 15 C 40 is reported utilizing ( R )‐4‐hydroxy‐2,6,6‐trimethyl‐2‐cyclohexen‐1‐one ( 4 ) as a…
The subject of gradient-index optics dates from the 1850s. However, only in the last 10 years has it been possible to design lenses, manufacture materials, measure the properties, and fabricate lens elements. The current status of gradient-index optics is reviewed.
The complex dielectric constant ϵ = ϵ′– jϵ″ of single crystals of squaric acid C4H2O4(H2SQ) was examined at around 100 MHz and between 2 and 8 GHz as a function of temperature. In the GHz range the imaginary part ϵ″ can be well described by the beginning of a monodispersive relaxation, whose relaxation frequency slows…
The anomalous photovoltaic effect referred to here is obtained fro crystals without a centre of symmetry. The spatially oscillatory photovoltaic current is investigated and the photovoltaic coefficients kijk for SbSI and ZnS determined. These coefficients are k31 = 4 × 10−8 Acm/W, k32 = 3 × 10−8 Acm/W, and k33 = (2 to…
The synthesis is described of four new cleavable, photosensitive, heterobifunctional cross-linking reagents for use in examining membrane organization: 4'-azidoazobenzene-4oxysuccinimide ester (1), N-[4-(p-azidophenylazo)benzoyl]-3-aminopropyl-N'-oxysuccinimide ester (2), N-[4-(p-azidophenylazo)benzoyl]-6-aminohexyl-N…
Optical materials for the 8 - 13 micron waveband are discussed and a range of high performance infrared telescopes incorporating chalcogenide glass is described.
The valence states of Fe and the charge compensation by oxygen vacancies of Fe57-doped BaTiO3 are studied by the Mössbauer effect and gravimetry as a function of O2 partial pressure. By preparational and analytical effort, it is ensured that the dopant homogeneously substitutes Ti4+ in the BaTiO3 lattice (up to 1.2 mo…
The perovskites Pb(Sc1/2Nb1/2)O3 and Pb(Sc1/2Ta1/2)O3 can be obtained in a disordered state by means of a synthesis at high temperature (1250 to 1500°C). Ordering of the trivalent and pentavalent ions occurs during annealing at lower temperatures. The kinetics of this ordering process are investigated by means of X-ra…
Electro-optical measurements of the electric field along solid insulator/vacuum interfaces have been made to determine the mechanisms associated with fast (ns) insulator flashover. Data showing the temporal and spatial performance of the insulator surface fields prior to and at flashover are presented. The results sho…
By modifying the surface plasma mode on a bare metal surface with an ultrathin film deposited on the metal, we measured the film thickness by attenuated total reflection (ATR). Various factors causing measurement errors are estimated with numerical examples. As a result, for example, it is shown that for some thicknes…
The vibrational averaging theory of Kern and Matcha is extended, at the harmonic level of approximation, to the case where the molecular property under investigation can itself lead indirectly to a perturbation of the vibrational levels of the molecule. It is found that contributions arising from this perturbation can…
The observation of a frequency-dependent conductivity ($\ensuremath{\sigma}$) and dielectric constant ($\ensuremath{\epsilon}$) in Nb${\mathrm{Se}}_{3}$ is reported. In both charge-density-wave phases a strong frequency dependence and huge dielectric constant are observed below 100 MHz, with greatest effects observed…
The heat capacities of LaNi5, α-LaNi5H0.36, and β-LaNi5H6.39 were measured from 5 to 300 °K, and in the case of LaNi5 also from 300 to 350 °K. Various special techniques and unusual circumstances involved in the measurements and calculations are described. A slight enhancement of the heat capacity of β-LaNi5H6.39 was…
While thin films of TiN and TaN are good diffusion barriers in contact structures which use nickel or gold as a top layer, they show poor barrier properties if aluminum is used as a top layer. It is shown in this letter that stable high-temperature contacts on silicon semiconductor devices can be produced by using int…
Optical spectra of the elpasolite hexachloride compounds Cs2NaLnCl6, where Ln represents one of the lanthanide ions, are analyzed with a crystal-field Hamiltonian of Oh symmetry. Crystal-field parameters, Bnm, are found that minimize the rms deviation between calculated and experimental energy levels for Ln=Ce, Pr, Nd…
The complete determination of the crystal structure of solid nitromethane has been obtained from single crystal x-ray diffraction and neutron powder diffraction data. The structure is orthorhombic, space group P212121 with a=5.1832 Å, b=6.2357 Å, c=8.5181 Å at T=4.2 K, and Z=4. Two models were used to describe the the…
Extensive electrical resistivity and Seebeck-coefficient measurements are reported for ${({\mathrm{V}}_{1\ensuremath{-}x}{\mathrm{Cr}}_{x})}_{2}{\mathrm{O}}_{3}$ single-crystal alloys in the range $0\ensuremath{\le}x\ensuremath{\le}0.1$. For $0\ensuremath{\le}x\ensuremath{\le}0.005$ a metal-insulator transition is enc…