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A flux growth technique for synthesizing FeBO3 single crystals of high structural perfection was developed. The high structural quality of the synthesized FeBO3 crystals was confirmed by means of double-crystal X-ray diffraction analysis both in Laue and Bragg geometries. The diffraction rocking curves taken locally and integrally over the surface are in excellent agreement with the calculated curves. Some macrodefects were revealed by X-ray topography in the crystal volume. However, the local defects do not prevent the use of defect-free regions of the crystal for synchrotron Mössbauer experiments.

Time-resolved technique of X-ray diffraction curve measurement was implemented at a laboratory X-ray source using a high-speed data acquisition system. The time resolution of up to 100 µs was achieved via this X-ray diffractometry technique in the experiment of rocking curve dynamics measurement in a piezoelectric lanthanum-gallium silicate crystal under the influence of high voltage periodic pulsed electric field with an amplitude of 3.08 kV/mm corresponding to the pre-breakdown state. This perturbation caused a quick angular shift of the rocking curve caused by crystal lattice deformation due to the piezoelectric effect. The absence of the diffraction curve broadening effect was shown as well as the absence of the other significant relaxation-like variations of the curve parameters which are inherent for the migration of charge carriers (ions or vacancies) under the external electric field.

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The dynamics and anisotropy of the formation processes of near-surface structures in paratellurite (α-TeO2) single crystals due to the migration of charge carriers induced by an external electric field are studied by x-ray diffraction and electrophysical methods. Significant yet reversible variations in the parameters of the diffraction rocking curves are observed. A diffraction peak broadening occurs for both polarities with a simultaneous shift of its maximum only occurring on the surface with a positive electric potential. For the [100] direction, a much higher velocity of saturation and relaxation processes was registered compared to the [110] direction. Moreover, a significant increase in the integral intensity of the 200 diffraction peak was observed. The electric field application along the fourth-order axis [001] does not lead to visible changes in the diffraction peak parameters. The dynamics and amplitude of the diffraction peak variation reflect the structural changes in the thin near-surface region of the crystal volume. This corresponds to the measured kinetics and value of the electric conductivity and the formation of the electrical double layer close to the insulator–metal interface, which is attributed to the oxide ion migration process from the crystal volume to its surfaces. The thickness of the structure formed close to the surface is estimated by mathematical calculations (the Debye screening length) and by x-ray diffraction (a layer with mechanical deformations) obtained at different diffraction orders. The experimental data are compared with the results of the x-ray diffraction peak simulations considering the crystal lattice strain with the depth attenuation.

Examining forbidden reflections provides valuable information on electronic states and the local environment of resonant atoms in crystals. Experimental studies of two forbidden reflections 002 and 100 in TeO2 single crystals were performed at photon energies close to the L1 tellurium absorption edge. It was found that the spectral form corresponding to these two reflections looks almost identical, which is completely unexpected for a highly anisotropic material. Theoretical consideration shows that only one component fxy of the tensor describing dipole-dipole resonance scattering contributes to the 002 reflection, while two components fxy and fxz correspond to the 100 reflection. Numerical calculations show that the latter tensor component is comparable to the first one, but the combination of several geometric factors leads to the fact that its contribution to the spectrum is negligible. This explains the experimentally observed results. The finding shows a way for targeted investigation of single tensor components and makes it possible to compare different spectra and use them the study the physical phenomena in functional materials.

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