Materials Literature
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Abstract Three polyethyleneoxide samples of molecular weights ranging from 6,000 to 28,000 have been studied with low‐angle X‐ray diffraction and dilatometry techniques. The thickness of the lamellae, the number of folds of the polymer chains, and the degree of crystallinity have been determined as functions of the cr…
Abstract In addition to the six liquids for which the results of viscoelastic measurements are reported in part I, studies have also been made on a further eight liquids which differ widely in molecular composition, namely: squalane, tri(β-chloroethyl) phosphate, tri(o-tolyl) phosphate, tri(m -tolyl) phosphate, tris(2…
Size-effect oscillations in the Hall resistivity have been studied in a monocrystal of highly pure cadmium at liquid-helium temperatures. Samples ranging in thickness from 2.01 to 0.09 mm were prepared from a single monocrystal by successively reducing the thickness using spark planing followed by electropolishing. Th…
The effective elastic constants of CdS have been measured by the ultrasonic pulse-echo method as a function of hydrostatic pressure to 4 kbar. The logarithmic pressure derivatives determined were $\frac{d\mathrm{ln}{C}_{11}}{\mathrm{dP}}=3.56$, $\frac{d\mathrm{ln}{C}_{33}}{\mathrm{dP}}=3.44$, $\frac{d\mathrm{ln}{C}_{1…
A formula for the phonon-drag part ${S}_{g}$ of the thermoelectric power in metals is obtained by assuming that the electron scattering processes can be described by a relaxation time $\ensuremath{\tau}(\mathrm{k})$. The formula differs from the simplest variational expression only by having extra factors of $\ensurem…
The specific heat of a ``splat''-formed amorphous alloy of gold-silicon-germanium exhibits a very steep rise with increasing temperature near 295°K to a peak and then begins to fall before crystallization occurs. These last Cp values fall on a reasonable extrapolation of the high temperature Cp-T relation found for th…
A study of the 7Li nuclear magnetic resonance in a LiNbO3 single crystal is made and the electric field gradient at the lithium site is determined. Electric-field-gradient calculations indicate that the net charge on the niobium is +1.59 while that on the oxygens is −0.86. This shows that the niobate ion is predominat…
Paramagnetic DyMn2O5 crystallizes in the orthorhombic system with lattice constants a=7.2940±0.0008, b=8.5551±0.0008, and c=5.6875±0.0008 Å, in the space group Pbam(D2h9). There are four DyMn2O5 per unit cell. The crystal structure was solved by a combination of three-dimensional Patterson and Fourier series and refin…
The kinetics of solidification of 1,3,5-tri-α-naphthylbenzene have been studied from 25° above the glass temperature (69°C) almost to the crystal thermodynamic melting point (199°C). The crystal growth rate has been analyzed using current theories of crystallization and a mechanism for crystal growth has been proposed…
The first-order Raman spectra of CaW${\mathrm{O}}_{4}$, CaMo${\mathrm{O}}_{4}$, SrW${\mathrm{O}}_{4}$, and SrMo${\mathrm{O}}_{4}$ have been obtained. All theoretically predicted vibrations have been observed, and assignment has been given for the internal vibrations of the tungstate and molybdate ions as well as for t…
The electron paramagnetic resonance of C${\mathrm{H}}_{3}$N${\mathrm{H}}_{3}$Al${(\mathrm{S}{\mathrm{O}}_{4})}_{2}$\ifmmode\cdot\else\textperiodcentered\fi{}12${\mathrm{H}}_{2}$O (MASD) doped with ${\mathrm{Cr}}^{3+}$ was studied from 90 to 300\ifmmode^\circ\else\textdegree\fi{}K. At the first-order ferroelectric Curi…
The first-order magnetic-transition temperature in MnAs has been measured as a function of both increasing and decreasing pressure. A critical pressure ${P}_{c}\ensuremath{\sim}4.6$ kbar has been obtained for the range of stability of the hexagonal phase. The pressure hysteresis increases with decreasing temperatures.…
The polarization associated with the vibrations of a complex lattice can be discussed by assigning apparent charges to the individual ions. These apparent charges can be calculated for a lattice of electrically polarizable ions by a consideration of the local dipole fields if polarization due to short-range forces is…
The lattice dynamics of the perovskite-type ferroelectric KTa${\mathrm{O}}_{3}$ has been studied by inelastic neutron-scattering techniques. In particular, the temperature dependence of the soft ferroelectric mode, namely a transverse optical mode at $q=0$, has been studied between 4 and 295\ifmmode^\circ\else\textdeg…
Conductivity, Hall-effect, and Seebeck-coefficient measurements on single-domain crystals of $n$-type BaTi${\mathrm{O}}_{3}$ are described. In the cubic phase above 126\ifmmode^\circ\else\textdegree\fi{}C, the electron mobility is 0.5 ${\mathrm{cm}}^{2}$/V sec. When the material becomes tetragonal, the mobility perpen…
The rates of radiative and nonradiative decay were determined for several excited states of ${\mathrm{Er}}^{3+}$ in La${\mathrm{F}}_{3}$ from calculated spontaneous emission probabilities and measured lifetimes. Electric-dipole, magnetic-dipole, and electric-quadrupole transition probabilities were evaluated using int…
A general method of obtaining many-electron wave functions which are eigenfunctions of ${\stackrel{^}{S}}^{2}$ and which also satisfy Pauli's principle is developed. This method is based on the properties of the irreducible units of the group algebra of the symmetric group. Using this method, expansions of the exact w…
Abstract The thermal conductivity of crystals of holmium ethylsulphate has been measured in the range 1 to 4·25°K in zero magnetic field and also in fields up to 53 kG, applied parallel to the hexagonal axis. The change in the thermal resistivity in a field is characterized by two maxima separated by a local, temperat…
Abstract The interpretation of X-ray and neutron diffraction data in accurate studies of crystal and molecular structure requires the development of a new structure factor formalism. The formalism normally employed in structure analysis fails to recognize antisymmetric features associated with nonspherical atomic char…
Single-crystal foils of the compound Bi2Te3 were irradiated with 7.5-MeV protons at two levels of flux to the same integrated dose of 5.5×1018 protons/cm2. The specimens were examined by transmission electron microscopy. After irradiation with a flux of 1.8×1013 protons/cm2·sec, clusters of point defects ranging in si…