Materials Literature
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PLZT electrooptic ceramics were fabricated by a unique atmosphere sintering technique. The ceramics produced were significantly more transparent than those obtained by ordinary O 2 sintering methods; in fact, they were comparable in transparency to those obtained by hot‐pressing. To achieve good transparency, the powd…
Reviews the contribution that transmission electron microscopy has made to the understanding of the mobility and clustering of point defects in fcc and bcc metals. The first part of the paper considers the nucleation and growth of vacancy clusters in quenched fcc metals. In the second part the complex subject of irrad…
Abstract The lattice vibrations of Mg 2 SiO 4 forsterite single crystal have been studied using infrared and Raman techniques. The site symmetry method allows to study the degeneracy lifting of the silicate ion vibrational levels and to assign the modes of vibration (45 infrared active modes and 36 Raman active modes)…
The effects of temperature [(4-500)\ifmmode^\circ\else\textdegree\fi{}K] and hydrostatic pressure (0-4 kbar) on the static dielectric constants ${\ensuremath{\epsilon}}_{a}$ and ${\ensuremath{\epsilon}}_{c}$ and on the frequencies of the four Raman-active phonons ${B}_{1g}$, ${E}_{g}$, ${A}_{1g}$, and ${B}_{2g}$ of si…
Performance and reliability of amorphous semiconductor devices that deal with the handling of information in the form of switching, modulation, storage, and display are discussed. Structural changes between a disordered and a more ordered state and the concomitant large change in many material properties offer the pos…
The stability of cylindrically symmetrical line disclinations is examined by continum theory calculations and topological arguments, to show that these singularities can almost always be replaced by a continuous structure of lower energy. The calculations are applied to the four basic types of index ± 2 structures. Ex…
The theory of the diffuse scattering by point defects and by defect clusters is reviewed. For a small concentration of statistically distributed point defects the symmetry of the long ranging part of the displacement field and the strength of the defects can be obtained from scattering measurements close to the recipr…
SUMMARY: Staining a marine bacterium with Ruthenium Red and Alcian Blue demonstrated an extracellular, compact acidic polysaccharide layer, which was involved in bacterial adhesion to surfaces. The adhesive substance was present on suspended bacteria and appeared to assist adhesion when they were forced into contact w…
A group of transparent ferroelectric hot‐pressed (Pb 0.92 La 0.08 )‐(Zr 0.65 Ti 0.35 ) 0.98 O 3 specimens with controlled grain size and constant porosity and a group of similar specimens with controlled porosity and constant grain size were prepared. The electrical and optical constants and polarization‐reversal prop…
The structure of alpha -phase potassium nitrate (KNO 3 ) has been determined at room temperature (25 degrees C) and closer to the alpha to beta transition temperature at 100 degrees C, from three-dimensional neutron diffraction data. The present results indicate that the potassium atoms experience small but significan…
The first stages of oxidation of niobium (NbOx) have been studied by electon microscopy. Two phases, called NbOxI and II were detected. A study of NbOz will be published elsewhere. Niobium has been oxidized by a wet argon flow on thin foils or powders, heated at temperatures from 350 up to 400°C. NbOxI, which has the…
The phase diagram and crystal structure of vanadium–deuterium alloys have been studied by means of neutron and X-ray diffraction as well as heat capacity measurements. In addition to a disordered solid solution (α-phase), the following three ordered phases have been found at relatively low temperatures, i.e. a β-phase…
The results of measurements on the conductivity of single crystals of SnS2 in a direction parallel to the c-axis are given. Prior to forming, space charge injection is shown to be the predominant mechanism and subsequently for the formed crystal the relation between current and voltage is I ∝ Un where n may be as high…
Differential thermal analysis and thermogravimetric analysis of sodium azide diluted with sodium chloride both show one major peak followed by a second minor one. This is interpreted as indicating the occurrence of two distinct decomposition processes. The activation energy of the first, major process was 36 kcal/mol,…
A complete diagonalization of the matrices for the electrostatic, spin-orbit, and crystal field interactions for Sm3+ in LaCl3 has been carried out using a truncated set of basis vectors containing 42 of the 73 LS states. This diagonalization allowed many new assignments to be made. Corrections of some of the centers…
The lattice dynamics, second- and third-order elastic constants, and the anisotropic thermal expansion of hexagonal titanium are worked out using Keating's approach. The ten third-order elastic constants are calculated using five third-order parameters. The experimental measurements on the pressure derivatives of the…
Several substituted pentaerythritol compounds [R—C(CH2OH)3, where R = COOH, CH3, NO2 and NH2] have been found to undergo phase transitions to plastic crystals. With the exception of R = NH2 (which has only one detectable diffraction line in the plastic state), the crystals are f.c.c., a ≃ 8.9 Å.
The drift mobility of excess holes has been investigated in undoped NiO crystals using a transient technique with electron-beam excitation. Specimens with low-impurity content were grown epitaxially from the gas phase. At room temperature ${\ensuremath{\mu}}_{h}$ lies between 20 and 50 ${\mathrm{cm}}^{2}$ ${\mathrm{V}…
Lithium metavanadate is monoclinic with a = 10.158(2), b = 8.4175(9), c = 5.8853(9) Å, β = 110.48(2)° and probable space group C2/c. The structure, refined by least-squares to a ωR = 0.033 using 851 reflections, is isotypic with LiAlSi 2 O 6 (spodumene) and LiFeSi 2 O 6 . Bands of Li—O edge-shared octahedra run parall…
The paramagnetic behavior of localized states in amorphous chalcogenide alloys and the tetrahedrally coordinated amorphous germanium has been studied by ESR experiments. No signal has been detected in any of the chalcogenide glasses, prepared by quenching from the melt, with a sensitivity of about ${10}^{11}$ spins/G…