A high pressure technique for the direct synthesis of polycrystalline HgTe in quartz ampoules is presented. An excess of mercury as well as a quasi-static regime of the inert gas pressure al melt temperatures up to 750 degrees C have been used. X-ray diffraction and SEM confirmed the structural homogeneity of the synthesized material.
Mossbauer measurements performed on Fe100-xGdx thin films and on Fe80-xGdxB20 both as thin films and ribbons show a dependence of the spins orientation and [H-hyp] versus temperature, Gd content and preparation conditions. Increasing the Gd content, the initial low anisotropy disappears and [H-hyp] decreases. A sharp increase of the anisotopy with temperature in ribbons with low Gd concentration is evidenced.
DOI: 10.1080/00914039408028570
Electron spin resonance investigations of the thermo-oxidative degradation of trans-polypentenamer rubbers, containing various stabilizers, are reported. The dependence of the resonance line parameters on the degradation time and temperature as well as the effect of various stabilizers on the resonance line are studied in detail. The activation energies for the generation of free radicals, the reaction order for the overall generation of free radicals and the associated constant rate, are estimated.
DOI: 10.1080/15363839408009551
The structure of pollycrystalline C60 films prepared by sublimation from 99.9% pure C60 powder and from graphite soot was investigated by X-ray diffraction. A complex fcc (111) line was found in the former samples. Comparison of experimental and simulated (111) profiles allowed to assess quantitatively the degree of stacking disorder introduced during the growth of the film. Probabilities could be derived for continuation of already started fcc and hcp sequences, thereby characterizing the statistical microstructure of the C60 films. Also, the relative magnitudes of inter- and intra-layer disorder can be estimated. The films deposited from graphite soot show a high structural disorder.
The present paper is a review of the data about the dislocations in the as-grown quartz crystal. The work presents some general considerations about dislocations, their origins and causes, methods of their observation and techniques to reduce the dislocations density. It is also shown a method to obtain a new shape crystal used in the positive X-seeds preparation.
DOI: 10.1016/0141-3910(94)90065-5
Electron spin resonance (ESR) investigations of polyethylene, irradiated with accelerated sulphur ions, are reported- The temperature dependence of resonance line parameters in the range 20-260-degrees-C, has been studied. Additional ESR data on polyethylene irradiated with neutrons as well as on polyethylene thermally degraded in air are presented. The nature of the free radicals induced by irradiation is discussed.
A method for the single crystal growth of Yttrium Iron Garnet (YIG) in a PbO/PbF2/B2O3 flux mixture with a melt cooling rate of 1-2.5 degrees C/h is described. In order to keep constant the crystal stoichiometry as well as its specific structural and magnetic properties at such high rates of the cooling process, a previously sintered polycrystalline garnet has been used as raw material. The YIG single crystal quality was checked-up by metallographic analysis, X-ray diffraction, SEM, and magnetic susceptibility measurements.
Evidence for a frozen spin ground state and a mixed magnetic ordered and paramagnetic state at intermediate temperatures was found in Fe-57-doped LiNiO2, using Mossbauer spectroscopy. The magnetic measurements, in agreement with Mossbauer data, suggest short-range ferromagnetic correlations at low temperatures and the occurrence of a paramagnetic phase below the spin freezing temperature.
In-field Mossbauer studies have been performed on the Li-0.5(1+t)(l+r)Fe2.5-1.5tTitO4 system with 1.10 less than or equal to t less than or equal to 1.40. The disordered magnetic properties depend strongly on the chemical disorder and local order induced by thermal treatments. The results are in agreement with low- and high-field magnetization measurements. Locally canted states are observed, with the degree of magnetic disorder depending on the composition and (or) the local chemical disorder.