Materials Literature
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Measurements of the electrocaloric effect in crystalline Rochelle salt throughout the ferroelectric range have been made and have been used to determine the Devonshire "dielectric stiffness" coefficient, the ferroelectric Curie temperatures, and the spontaneous polarization close to both Curie temperatures. The result…
The migration of slab, cylindrical, and spherical zones through a block of solid under the influence of a temperature gradient has been analyzed theoretically. The relative rates of migration are in the above order if KS>KL and the reverse order if KS<KL (K=thermal conductivity, S=solid, L=liquid). The m…
The relative intensities of the transitions occurring in the fluorescence spectrum of Eu(C2H5SO4)3·9H2O have been measured at 77° and 4°K. The strengths of both the ``forbidden'' electric dipole transitions and magnetic dipole transitions which were observed are compared to theoretical expressions and the results are…
Dislocation-free crystals of the semiconductor elements germanium and silicon and the compounds indium antimonide and gallium antimonide have been deformed in tension over a range of temperatures, initial dislocation densities, and strain rates. In all of the dislocation-free crystals, plastic deformation occurs at st…
It is shown that in the b.c.c. lattice the crystallography and the commonly observed low stacking-fault energy on {112} lead to the prediction that ½<111> screw dislocations will each dissociate into three 1/6<111> partials situated on {112} planes which intersect along the axis of the original screw dislocation. Calc…
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Artificial layered structures that produce sharp diffraction of x rays are described. The structures were made by alternately evaporating 140 Pb and Mg layers onto a glass slide (d=27 Å). The diffracting efficiency of the layered structures is compared with other structures used in soft x-ray spectroscopy. The usefuln…
The melting temperature of linear polyethylene has been obtained as a function of the time and temperature of crystallization. Recrystallization was minimized by a special melting procedure. By interpreting the melting points as characteristic of a given lamellar thickness, it was found that the thickness of crystals…
The specular reflectance of aluminum films evaporated in ultra-high vacuum has been measured with precision in the 0.3- to 32-μ wavelength region. The measured reflectance of these films, which is good to ±0.1%, is significantly higher than that of films prepared under the usual high-vacuum conditions. The reflectance…
A study, by high‐temperature diffractometry, of the monoclinic‐tetragonal phase changes in pure ZrO 2 and HfO 2 disclosed that the hysteresis loops associated with the transformations have similar shapes which are typical of many martensitic phase changes, but that the widths of the loops differ greatly for the two ma…
Analytical equations of the types required to define ballistic perforation dynamics are developed. These equations concern both blunt and sharp-nosed fragments, perforating plates normally and at oblique impact angles. Residual velocities are defined in terms of magnitude and direction. Analytical models and confirmin…
The high-temperature thermal conductivity of a disordered semiconductor alloy is derived using the Klemens-Callaway theory. It is assumed that the reciprocal relaxation times depend on frequency $\ensuremath{\omega}$ as ${\ensuremath{\omega}}^{4}$ for strain and mass point defects and as ${\ensuremath{\omega}}^{2}$ fo…
A new method of computing the Coulomb self-energy of uniform axial figures is developed. The energy is expressed as a sum of slice-slice interactions plus the self-energy of each slice. Analytical formulas are derived for these energies and are presented in numerical tables. The method is tested numerically by compari…
The thermoelectric effect in single-crystal cuprous oxide, measured at temperatures of 500° to 1130°C and oxygen pressures P of 160 to 2×10—6 Torr, was found always to be positive, indicating that the material is a p-type semiconductor in these ranges of conditions. Plots of the thermoelectric power Q vs 1/T at differ…
The magnetic structures of tetragonal chromium-modified ${\mathrm{Mn}}_{2}$Sb have been determined by neutron-diffraction studies of single crystals. Compositions of ${\mathrm{Mn}}_{2\ensuremath{-}x}{\mathrm{Cr}}_{x}\mathrm{Sb}$ for $x$ from 0.023 to 0.10 were examined. Three magnetic structures have been observed, de…
The curves of the thermal conductivity versus temperature of some insulating crystals (alkali halides) which are doped with certain impurity centers exhibit a distinct indentation. This suggests a relaxation time of some resonance nature, which is independent of the temperature for molecular impurity centers (KCl: KN$…
The emission excited in the association of atomic oxygen and nitrogen has been studied in a fast-flow low-pressure system by photoelectric and spectroscopic methods. The absolute rates of excitation of the products of these associative processes have been measured, and the effects of added quenching gases have been in…