Materials Literature
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The effect of Brownian motion of particles in a statistically homogeneous suspension is to tend to make uniform the joint probability density functions for the relative positions of particles, in opposition to the tendency of a deforming motion of the suspension to make some particle configurations more common. This s…
Dielectric and elastic constants of $\mathrm{K}{\mathrm{Ta}}_{1\ensuremath{-}x}{\mathrm{Nb}}_{x}{\mathrm{O}}_{3}$ are presented as a function of $x$ and of the temperature. For $x=8\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$, the system exhibits the characteristics of a ferroelectric at the displacive li…
Effective charges, q, in ternary and complex systems are estimated. The semiempirical method of Suchet (1965) is extended to ternary compounds such as manganites and ferrites while the semi-experimental method of Gianturco and Coulson (1968) is applied to complex Co-Zn ferrites and cobalt complexes. An attempt is made…
Abstract The H4 vibronic band is the dominant end product of annealing irradiated diamonds which contain impurity nitrogen in one specific aggregated form, the ‘B’ form. This paper reports uniaxial stress experiments on the H4 zero phonon line, and establishes it unambiguously as a (110) electric dipole transition at…
Doped polyacetylene forms a new class of conducting polymers in which the electrical conductivity can be systematically and continuously varied over a range of eleven orders of magnitude. Transport studies and far-infrared transmission measurements imply a metal-to-insulator transition at dopant concentrations near 1%.
The insulator–metal transition of VO2 and VO2 doped with Re is studied by means of DTA, X-ray diffraction, magnetic susceptibility, and electrical conductivity measurements. A linear decrease of the transition temperature of 18 K/at% Re is observed. The low-temperature phase is found to be temperature-independent para…
Photoluminescence of GaSe is measured between 4.2 and about 40 K. The spectra of many samples are classified into three types. The first type has only one broad peak at about 2.04 eV, and the second type has two sharp lines at 2.096 and 2.088 eV followed by some lines at the lower energy side. The last one contains a…
The substitution of Ca2+ ions in magnetite is studied, mainly by Mössbauer spectroscopy. The Ca2+ ions are located at the tetrahedral sites and the conduction electrons can be described by a band model. The magnetite structure can at most contain 6.67 wt% of Ca. The presence of a Ca2+ ion at an A-site decreases the hy…
An equilibrium method for the determination of the vacancy formation volume in many metals is provided by the trapping of positrons at vacancies. Utilizing a Bridgman press and angular-correlation counting techniques, the vacancy formation volume in metallic indium has been determined to be 6.1 \ifmmode\pm\else\textpm…
The visible interaction of low-intensity ultrasonic waves with a nematic liquid crystal may be explained simply by the hypothesis of a torque tending to orient LC molecules perpendicular to the vibrations. It is shown how this torque can be related to anisotropic attenuation of ultrasound and minimization of propagati…
Measurements of the thermal impedance across copper-epoxy-copper sandwiches have been made over a temperature range of 0.05-10 K. The data are consistent with the suggestion that only low-frequency phonons contribute to thermal transport across the sandwich. As a result the apparent thermal boundary resistance at the…
We have measured the Auger, electron-energy-loss, and optical-transmission spectra of $\ensuremath{\alpha}\ensuremath{-}{\mathrm{Al}}_{2}{\mathrm{O}}_{3}$ and Na $\ensuremath{\beta}\ensuremath{-}{\mathrm{Al}}_{2}{\mathrm{O}}_{3}$ from 0 to 45 eV and from 3 to 6 eV, respectively. Although Auger measurements were not ab…
A thin (∼400 Å) LPE In1−xGaxP1−zAsz ’’trap’’ on the p-type side of an InP junction [Eg(InP)−Eg(InGaPAs) ≡ΔE∼245 meV], is filled by injection to a high enough density to make it possible to observe confined-particle states and laser modes in a 70-meV (≳600 Å) range. The position of the modes is in good agreement with t…
Low-temperature Raman scattering results for stage 1, 2, and 3 graphite-alkali-metal intercalation compounds are reported for in-plane modes using the Brewster-angle back-scattering geometry. Detailed full spectra are presented for stage 1, 2, and 3 compounds of graphite-Rb at 77 K. Particular attention is given to th…
The complex dielectric constant has been measured at five audio frequencies over the temperature range 5.5-400 K for calcium fluoride doped with 13 different rare earths. Five relaxations are observed which are characteristic of rare earths in calcium fluoride. Two of the relaxations do not exist for large rare-earth…
The elastic constants K11, K22, and K33 of some members of two homologous series of nematic liquid crystals, the p,p′-di-n-alkyl and p,p′-di-n-alkoxy azoxybenzenes, are reported. Both K11 and K33 become greater with increasing alkyl chain length, while the ratio K33/K11 decreases along the series. For small alkyl chai…
The effects of compositional, vibrational, long-range positional, and topographical disorders upon the angle-resolved photoemission spectra of tightly bound valence electrons are investigated. In order to take into account the strong potential sensed by the electron in the vicinity of the atomic core, an augmented-pla…
Raman and far-infrared reflectivity spectra have been obtained for both stoichiometric and nonstoichiometric Ti${\mathrm{Se}}_{2}$ above and below the transition temperatures corresponding to formation of the $2{a}_{0}\ifmmode\times\else\texttimes\fi{}2{c}_{0}$ superlattice. In the normal phase above ${T}_{c}$ Raman-a…
A first-principles energy-band study of the metallic rutile phase of V${\mathrm{O}}_{2}$ using a general crystal potential and an expansion of the Bloch functions in a linear combination of atomic orbitals is reported. The results are compared with previous work and experimental optical, x-ray absorption and emission,…
The transport properties of the linear-chain metal Nb${\mathrm{Se}}_{3}$ are anomalous. Giant increases in the dc resistivity appear at 145 and 59 K, suggestive of charge-density-wave (CDW) formation. These anomalies show breakdown effects with applied electric fields as low as 0.1 V ${\mathrm{cm}}^{\ensuremath{-}1}$.…