Materials Literature
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X-ray diffraction measurements have been made of the wavevector and intensity of satellite diffraction spots as a function of temperature in two examples of crystal B phases. In N-(5-n butyloxybenzylidene)-4-n-heptylaniline (5O.7) a simple sinusoidal layer modulation of fixed wavelength grows in amplitude with decreas…
For pt.II see ibid., vol.15, p.3445 (1982). The authors consider diffusion from a surface y=0 into a solid containing a regular array of d dislocations per unit area, all normal to the surface and each represented as a pipe of radius a within which the diffusion coefficient D' is very much greater than that, D, for di…
Calculations of the electronic structure of WO 3 suggest that the detailed crystallographic arrangement determines rather sensitively the size of the semiconducting energy gap. This increases from 1.6 eV in the perovskite-like cubic approximation to the structure, as used in the only previous study, to 2.4 eV in the f…
The luminescence decay time of the 1.945 eV centre has been determined as 13+or-0.5 ns for natural type Ib diamonds. For synthetic diamonds the value is slightly lower, probably because of competitive non-radiative recombination in these relatively impure crystals. The similarity of the decay time to that for the H3 c…
A review of the polymerization of cycloorganosiloxanes is provided. Cycloorganosiloxanes such as octamethyl cyclotetrasiloxane are the principal intermediate for the formation of high molecular weight polyorganosiloxane polymers. The ring opening reaction can be initiated through the use of suitable basic or acidic ca…
Heat capacity of As4S3 is measured in the range 100 to 500 K. The structural phase transition (β to α) and the crystalline-to-plastic phase transition (α to γ) are investigated and these phase transition temperatures are determined to be (422 ± 0.5) and (432 ± 0.5) K, respectively. The results are compared with those…
The ternary compounds PtMnGe, PtMnAl, FeNiIn, FeMnIn, FeNiGe, FeCoGe, FeMnGe, CoNiSn, FeNiSn, FeCoSn, and MnCoSn are found to crystallize in the hexagonal Ni2In structure. The lattice constants of these compounds are determined and their magnetic properties studied in the range 4.2 to 300 K. It is found that most of t…
Electrical conductivity of bull amorphous V2O5 obtained by splat cooling is measured in the temperature range 360 to 150 K. A continuous decrease of the activation energy W deduced from a plot of In (σT) vs. T−1 is observed in the whole range. Such a behaviour is typical of small polaron hopping in amorphous transitio…
The electrical conductivity and the thermoelectric power of some finely-divided cobalt and zinz ferrites near stoichiometry are studied as a function of firing temperature and atmosphere. It is determined that iron-excess ferrites obtained at low preparation temperature or firing in vacuum above 600 °C are of n-type a…
Recently, Alig, Bloom, and Struck have reported a simple model of ionization scattering in semiconductors and insulators. Their model is based upon the random-$k$ approximation to the transition rate for impact ionization, and upon a generic band structure with only two free parameters to describe all materials. The p…
We present a systematic study of thermal diffusivity in the nematic liquid crystalline phase of 4-4′-di-(n-alkoxy) azoxy benzenes and several other materials. The data allow to separate the respective contributions of the rigid central core and of the flexible aliphatic chains. For the component of the diffusivity ten…
AgCr${\mathrm{S}}_{2}$ is a quasi-two-dimensional superionic conductor for silver ions which shows a second-order phase transition at ${T}_{c}=673$ K. Well below ${T}_{c}$, AgCr${\mathrm{S}}_{2}$ is ordered and pyroelectric; above ${T}_{c}$ the silver ions are disordered and the phase is nonpyroelectric. The ion dynam…
In this paper we have completed an error analysis of the Buchdahl glass model for 813 glasses available from five manufacturers. A quadratic model has a standard deviation of 0.00002 and a maximum absolute error of 0.0001 in the visible spectral region. A cubic model has a standard deviation of 0.00005 and a maximum a…
From an analysis of $^{31}\mathrm{P}$ nuclear-magnetic-resonance spectra, the chemical nature and local bonding of phosphorus in samples of amorphous hydrogenated silicon ($a\ensuremath{-}\mathrm{S}\mathrm{i}:\mathrm{H}$) have been determined. Overlapping spectra of threefold- and fourfold-coordinated phosphorus may b…
Four-wave mixing from a regular array of uniformly shaped and sized silver particles has been observed. The measured conversion efficiency yields an enhancement in the particles' third-order polarizability by a factor of 900 over that of the bulk metal, and is found to be in satisfactory agreement with the enhancement…
Neutron diffuse scattering from powder samples of α-AgI type superionic conductors AgI, Ag 3 SI and Ag 2 S was measured using a triple-axis spectrometer with a fixed position of the energy analyzer so as to measure only the elastic scattering caused by a disordered distribution of cations. The disorder scattering curv…
Diffuse x-ray scattering studies of the quasi-one-dimensional conductor di-tetramethyltetraselenafulvalenium perchlorate [${(\mathrm{TMTSF})}_{2}$Cl${\mathrm{O}}_{4}$], both in its pristine form and when slightly doped with the sulfur analog tetramethyltetrathiafulvalene (TMTTF), reveal the formation of a low-temperat…
The spin-flip energy of donor-bound electrons is investigated in the semimagnetic semi-conductor ${\mathrm{Cd}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{Se}$. Temperature and magnetic field dependences are measured with the use of Raman scattering and calculated theoretically from a statistical-mechanical model. Res…
A simple method of measuring refractive indices of bulk materials using a prism coupling procedure is described. Refractive indices are determined from the measurement of the angle incident to the prism at which total reflection on the prism base breaks. This method is shown to possess the advantages of its simple pro…
Hydrogenated amorphous (a-C:H) films were prepared by rf-plasma deposition from benzene vapor. Complete optical absorption spectra from the UV to the IR (0.2–20.0 μm) have been measured. The optical gap depends linearly on hydrogen content and Eopt can be varied between 0.8 and 1.8 eV. For energies below Eopt the film…