Materials Literature
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We investigate the ac conductivity of glasses due to atomic and electronic hopping between sites with random space and energy separations. Several examples are considered including the structural model of glasses recently introduced by Anderson, Halperin, and Varma, and by Philips. We find that glassy materials should…
Abstract The rare-earth crystals DyVO4, DyAsO4 and TbVO4 undergo structural phase transitions at 14, 12 and 34 K respectively induced by a cooperative Jahn-Teller effect. An experimental investigation of the phase changes has been made using Raman scattering methods. For purposes of comparison, the Raman spectra of Dy…
Single-crystal x-ray investigations reveal charge localization in the insulating phases of ${\mathrm{Ti}}_{4}$${\mathrm{O}}_{7}$ and ${\mathrm{V}}_{4}$${\mathrm{O}}_{7}$. Chains of ${M}^{3+}$ and ${M}^{4+}$ sites run parallel to the pseudorutile $c$ axis, whereas the metal valences are disordered in the metallic phase…
Abstract The variation with pH of the viscosities of aqueous solutions of the following polyvinylpyridine oxide derivatives has been studied, viz. atactic poly(2‐vinylpyridine 1‐oxide), poly(2‐methyl‐6‐vinylpyridine 1‐oxide), poly(3‐methyl‐2‐vinylpyridine 1‐oxide), poly(5‐ethyl‐2‐vinylpyridine 1‐oxide), poly(4‐vinylpy…
Saturation magnetization, X-ray and neutron diffraction measurements were made on ferromagnetic alloys in the compositions Ni2MnSb, Ni2MnSn, and Co2MnSn. The compounds investigated have a crystallo-chemical structure of L21 type, with a partial disorder among NiSb atoms in the case of Ni2MnSb and Ni(Co)‒Mn atoms in t…
A structure determination of the orthorhombic phase of ${\mathrm{V}}_{0.95}$${\mathrm{Cr}}_{0.05}$${\mathrm{O}}_{2}$ based on powder data indicates that the probable space group is $F222$ and the room-temperature lattice parameters are ${a}_{o}=13.015$ \AA{}, ${b}_{o}=12.597$ \AA{}, and ${c}_{o}=5.795$ \AA{}. The stru…
Two thermoluminescence peaks are observed in KBr crystals that are x irradiated at room temperature. The 185\ifmmode^\circ\else\textdegree\fi{}C peak can be removed by annealing the crystal for several hours at 400\ifmmode^\circ\else\textdegree\fi{}C and is attributed to highly localized defects. The 152\ifmmode^\circ…
This paper reports new experimental results on the influence of scavengers on the yields of trapped electrons in γ-irradiated organic glasses, which show that: (1) Trapped electron yields observed minutes after irradiation decrease exponentially with scavenger concentration; (2) transfer of trapped electrons to scaven…
The long-range order in $\ensuremath{\beta}$-brass has been determined over the entire range of temperatures below ${T}_{c}$ from x-ray measurements of integrated intensities of superlattice Bragg reflections. Analysis of the data included allowance for the observed appreciable differences between Debye-Waller factors…
We have determined the thermionic parameters---true work function, $A$ constant, and normal energy distribution---for near stoichiometric NiO. The distribution was found to be Maxwellian, with the electron temperature matching the lattice temperature closely. The results show that the Fermi level in NiO is rather inse…
Infrared reflection spectra of NaF single crystal from 160 to 660 ${\mathrm{cm}}^{\ensuremath{-}1}$ as functions of temperature up to about 1000 \ifmmode^\circ\else\textdegree\fi{}K are presented. A Kramers-Kronig (KK) dispersion analysis is applied to these spectra. The optical constants, long-wavelength optic-phonon…
An expression is obtained for the lattice thermal conductivity of an anharmonic crystal by the method of double-time Green's functions using the energy-flux operator propounded by Hardy. The study uses cubic and quartic anharmonic terms in the crystal Hamiltonian. It is found that the nondiagonal part of the energy-fl…
The purpose of this paper is to present a quantum-mechanical theory of the inelastic scattering of slow electrons by long-wavelength surface optical phonons for simple models of an ionic crystal and for a nonionic crystal such as silicon. It is argued that a quantum-mechanical approach is necessary for this problem. H…
The quantization of the motion, perpendicular to the surface, of electrons in an inversion layer at the surface of a silicon substrate is experimentally verified by accurate capacitance measurements at 77 and 300 \ifmmode^\circ\else\textdegree\fi{}K. From the measurements the average distance of the electrons from the…
Raman scattering from the mixed crystal K${\mathrm{Ta}}_{0.64}$${\mathrm{Nb}}_{0.36}$${\mathrm{O}}_{3}$ (${T}_{c}\ensuremath{\approx}10$\ifmmode^\circ\else\textdegree\fi{}C) has been investigated as a function of temperature in the paraelectric and single-domain-ferroelectric phases. The phonon spectrum was found to c…
By Monte Carlo calculations in the canonical ensemble, we have studied some properties of a two-dimensional system of 170 long hard ellipses (whose axis ratio equals 6). This system can be considered as a two-dimensional model for a nematic liquid crystal. We have shown that this system exhibits two first-order phase…
The toroidal but parallel array of planes of unidirectionally oriented molecules believed to characterize cholesteric liquid crystals also gives rise to certain geometrical patterns. The reality of this structure is demonstrated by micrographic evidence.
The review presents a detailed summary of the current understanding of the phenomenon of corrosion fatigue in gaseous and in aqueous environments. The effects of gaseous environments at low and at elevated temperatures and the mechanisms which govern fatigue crack initiation and propagation in the presence and in the…
Abstract Phosphatschichten wurden erhalten durch anodisches Phosphatieren in Natriumphosphatlösungen (2,5 bis 5% Phosphat, PH 4,2 bis 5,4 Stromdichte 2,5 bis 5,0 mA/cm 2 ). Die Phosphatschichten (Schischtgemisch 7,3 bis 20 g/m 2 ) bestehen aus Ferri‐Ferro‐Phosphat, wobei das Verhältnis Fe 2+ :Fe 3+ von der Badzusammen…
The polarized Raman spectra of the room temperature (ordered) phase and the high temperature (disordered) phase of cesium nitrate have been recorded. The assignment of the spectral bands differs somewhat from earlier reports of the room temperature phase with a to/lo splitting of the ν3(E) band at ∼ 1350–1400 cm−1 rep…