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Mixtures of two liquid crystalline compounds (which do not exhibit antiferroelectric phases separately) show ferrielectric phase in a broad temperature range in 5:5 and 3:7 compositions. The dielectric spectroscopy technique was used for investigation of collective molecular motions in these mixtures. Two relaxation modes were detected in the ferrielectric phase. The temperature dependence of the...
Conductivity of two epoxy matrices based on the same monomer was compared. The epoxy monomer had symmetric structure and contained the biphenyl group which induced additional phase transitions in the pure material. Two amines responsible for different curing mechanisms were used to prepare the matrices. Wide ohmic regions were observed in both materials but quite high activation energy results in...
Formulae for relative impurity content in various parts of a crystal have been derived and analysis of sectorial and zonal distributions of impurities conducted. Contribution of volume diffusion controlled crystal growth for sectorial and tonal distributions of impurities in lopezite crystals has been evaluated as small in comparison with surface diffusion.
The paper describes the influence of the effect of light beam deviation from Bragg angle on the intensity of light diffracted on acoustic wave. The analysis was based on the results of numerical calculations. The calculations were made for several characteristic cases.
It is shown that the fourth-order electrooptic effect may be responsible for the temperature dependence of the quadratic electrooptic coefficients defined in terms of polarization. An example is given for the ammonium dihydrogen phosphate (ADP) crystal.
Results of Monte Carlo simulations for single-layer solid-fluid interface were compared with Bragg-Williams approximation, which describes the number of bonds between solid and fluid cells in Jackson's crystal growth model. The comparison shows that Bragg-Williams approximation produces much higher values than those resulting from simulations. The use of better approximations based on the results...
Transport processes enhanced by absorption of the volatile ethanol on the tetracene and p-quaterphenyl films are considered. Obtained results may suggest injection of the charge during chemisorptions. There was observed a deep modulation of conductivity due to absorption of ethanol, this dependence suggests some ability to utilize.
The deformations of homeotropic nematic layers induced by ac electric field of frequency f were studied numerically. Two kinds of nematic liquid crystals with small negative dielectric anisotropy, Δε < 0, were considered: (i) the non-flexoelectric nematic, (ii) the nematic characterised by the positive sum of flexoelearic coefficients e = e11 + e33 > 0. It was found that at sufficiently low...
Deformations of nematic layers induced by electric field were studied numerically. The role of very strong flexoelectric properties was considered. The threshold voltages for deformations were calculated for nematics with very low, moderate and high ion contents and characterized by negative dielectric anisotropy. The director distributions were also determined. When the sum of flexoelectric coefficients...
There were investigated the magnitude of the mobility and the type of the mechanism of the electron transport in the amorphous antrachinone layers. Antrachinone (C14H8O2) is the molecular crystal. The antrachinone molecules are planar, centrosymmetric and posses permanent dipole moment practically equal zero. The antrachinone layerss were obtained by evaporation in vacuum under the pressure of the...
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