A. M. Askhabov

Nonlinear effects in corundum and ilmenite in high frequency electromagnetic fields

This paper details the results of a comparative study of two materials having the same structure, but drastically different radiophysical characteristics. Corundum ceramic samples were synthesized from pure substances by firing a charge in air at 1450°C for 1 h. The second material was prepared from natural ilmenite without heat treatment using an epoxy polymer binder. Measurements of the transmission and reflection factors within the frequency range of 8–26 GHz indicate that corundum ceramic samples scatter electromagnetic radiation (EMR) exhibiting a pronounced dispersion of the reflection and transmission factors. On the contrary, ilmenite samples absorb EMR showing no dispersion at all. The differences in the radiophysical characteristics are due to the presence of magnetic impurities in the crystal lattices of corundum and ilmenite and the specific features of the spin-phonon interaction in dielectric and ferrite materials.

The kvataron model of fullerene formation

A new mechanism is proposed for the formation of fullerenes from clusters of a “latent” phase, which are referred to as kvatarons. According to this mechanism, hollow kvatarons initially arise in a supersaturated carbon-containing medium and then transform into rigid clusters (fullerenes) with characteristic icosahedral symmetry due to the formation of bonds between carbon atoms.

The Influence of Mechanical Deformation on the Optical Properties of Laminated As2S3, GeSe2 and As2Se3 Crystals

Reversible photostructural conversions (darkening and bleaching) attended by a shift of transmittance edge and by the photoluminescence fatigue effect are revealed. Upon mechanical treatment of crystals the maximum of the luminescence excitation spectrum shifts toward higher energies. The low-energy edge of the luminescence spectrum flattens, and emission intensity increases. The experimental results are interpreted within a configuration model of two stable structural states of molecular groups.

Ultrahigh-Pressure Liquation of an Impact Melt

Liquation structures were described in ultrahigh-pressure impact glasses of the Kara astrobleme (Pay-Khoy) with differentiation into the bisilica, aluminosilicate, and ore components for the first time. The sequence of differentiation of mineral phases upon solidification of an ultrahigh-pressure impact melt was established: coesite, silicate glass, augite, aluminosilicate glass of albite composition, and pyrite. The discovered impact glasses are highly resistant to postimpact alterations.

Dynamics of the Formation of Globular Silica Particles according to Dynamic Light Scattering

For the first time, the dynamics of the origination and growth of monodispersion spherical silica particles is studied by dynamic light scattering in the real-time mode. Experimental changes in the particle size and intensity of scattering during their formation and growth indicate the hierarchical formation of silica globules under various mechanisms of aggregation of particles.

Effect of mechanical deformations on the growth of crystals (according to atomic force microscopy data)

Nanosized morphological transformations occurring on the surface of a crystal in the area drawn by a probe needle during the growth of a scratch and the growth kinetics of crystals subjected to mechanical impact have been studied by atomic force microscopy (AFM). A series of experiments with mechanical impact on topographically different areas of a growing face (100) of a dioxidine crystal has been performed. It has been shown that even slight local contact between the probe needle and the surface on a nanoscale leads to essential crystallogenetic (morphological and kinetic) consequences, and its effect is perceptible for a long time. Among these consequences are the coarsening of stages, the appearance of great fluctuations in the growth rate of stages, the loss of morphological stability by the surface even at a distance of several tens of micrometers from the contact area, and also the phenomenon of simultaneous growth and dissolution in neighboring areas of stages.

Effect of preparation conditions on the optical and photoluminescent properties of glassy As2S3

We have studied the 77-K photoluminescent properties of As2S3 semiconducting glass prepared at different temperatures (T1 = 870 K; T2 = 1120 K; T3 = 1370 K) and cooling rates (v1 = 10−2 K/s, v2 = 1.5 K/s, v3 = 1.5 × 102 K/s). The results demonstrate that the structural, optical, and photoluminescent properties of semiconducting chalcogenide glasses can be tuned over a considerable range by varying the preparation conditions.

Effect of rare-earth impurities on the photoluminescence of Ge2S3 glass

The photoluminescence properties of Ge2S3 glass doped with rare-earth elements La, Ce, Gd have been studied in the temperature range of 4.2–300 K. It has been shown that these impurities do not form new levels responsible for emission. The variation in the principal parameters of the excitation and emission spectra with the concentration and nature of impurities has been estimated.

The influence of a high and low content of Au impurity on the photoluminescence of stoichiometric and nonstoichiometric arsenic sulfide

The photoluminescence and photoluminescence excitation spectra of stoichiometric and nonstoichiometric glasses with Au impurity were investigated for the first time at T=77 K. It is found that the photoluminescence spectrum of nonstoichiometric glasses with low content of impurity is split into two bands, one of which is impurity-induced.

Study of mechanical amorphization of mineral orpiment (As2S3) and arsenic and germanium selenide crystals by optical methods

Reversible photostructural transformations (darkening and clearing) accompanied by a shift of the edge transmission and a fatigue effect of luminescence have been found in deformed As2S3, GeSe2, and As2Se3 single crystals and powders at T = 77 K. The experimental results are interpreted based on the configurational model of two stable states of molecular groups.