The synchronization of laser and X-ray sources is essential for time-resolved measurements in the study of ultrafast processes, including photo-induced piezo-effects, shock wave generation, and phase transitions. On the one hand, optical diagnostics (by synchronization of two laser sources) provides information about changes in vibration frequencies, shock wave dynamics, and linear and nonlinear refractive index behavior. On the other hand, optical pump–X-ray probe diagnostics provide an opportunity to directly reveal lattice dynamics. To integrate two approaches into a unified whole, one needs to create a robust method for the synchronization of two systems with different repetition rates up to the MHz range. In this paper, we propose a universal approach utilizing a field-programmable gate array (FPGA) to achieve precise synchronization between different MHz sources such as various lasers and synchrotron X-ray sources. This synchronization method offers numerous advantages, such as high flexibility, fast response, and low jitter. Experimental results demonstrate the successful synchronization of two different MHz systems with a temporal resolution of 250 ps. This enables ultrafast measurements with a sub-nanosecond resolution, facilitating the uncovering of complex dynamics in ultrafast processes.

The dynamics of the diffraction peak 0012 parameters of LiNbO3:Fe crystals with a time resolution of less than 1 ns were recorded by synchronizing nanosecond laser pulses with electron bunches of the KISI-Kurchatov synchrotron source. The influence of a laser pulse (λ = 532 nm, t = 4 ns, energy density 0.6 J/cm2) at different polarization directions of the laser radiation causes a change in the peak intensity, which depends on the angle between the polarization direction of the laser radiation and the crystallographic axes. The obtained results are supplemented with wavelet analysis of experimental data. The observed polarization dependence correlates with published data on the photovoltaic effect.

Unusual time-delayed changes in the x-ray diffraction parameters of LiNbO3 and LiNbO3 : Fe crystals were observed under nanosecond laser impact. Subnanosecond time resolution in the registration of diffraction rocking curve (DRC) dynamics was achieved through the synchronization of a 4 ns laser pulse with the circulation phase of electron bunches within a synchrotron storage ring. The response of the crystals to optical impact resulted in a reversible center-of-mass shift and integral intensity decrease of the DRC recovering in similar to 35 ns. The dynamics of lattice deformation indicates the process of formation and subsequent decay of an electrical charged layer near the surface due to directed migration of photoelectrons as a result of the bulk photovoltaic effect. The drop in the integral intensity of the DRCs is apparently caused by a running wave generated by a sharp change in the deformation of the crystal lattice. In the case of the nominally undoped crystal, the time-delayed processes occur within the same time interval but with significantly smaller amplitudes.

Using X-ray topography, the distributions of deformations in the volume of two types of AT-cut quartz resonators of different sizes were obtained on laboratory and synchrotron X-ray sources. The comparison of X-ray topography data and the amplitude–frequency characteristics of the resonators was used to establish a correlation between the deformation patterns and the features of oscillatory processes for the operating modes and their harmonics, as well as for parasitic modes. A connection between vibrations at parasitic modes and their harmonics, which manifest themselves in an amplitude inhomogeneity, and the topology of the resonators has been found. The applied significance of the obtained results for the development and optimization of new designs of piezoelectric elements and the development of their manufacturing technology is pointed out.

The method and experimental cell for the X-ray diffraction diagnostic of crystalline materials exposed to magnetic fields have been described. It has been shown that the application of even weak magnetic fields (about several Oersteds) allows one to significantly reduce the diffraction contrast on X-ray topograms of FeBO3 and Fe0.94Ga0.06BO3 single crystals, which is due to a nonuniform distribution of magnetostriction strains, and thereby to improve the degree of their structural perfection. The magnetic domain structure of Fe1 –xGaxBO3 solid solution single crystals has been visualized. It has been found that small concentrations of diamagnetic Ga ions do not significantly change the configuration of domain walls in FeBO3-based crystals.

The possibilities of a new class of adaptive X-ray optical elements based on bending piezoelectric actuators for practical implementation of time-resolved experiments using X rays and synchrotron radiation-fast high-resolution X-ray diffractometry and fast X-ray absorption spectroscopy-are described. Examples of studies and results obtained using the proposed elements and the corresponding techniques are presented.

In this work, high-resolution triple-crystal X-ray diffractionand reciprocal space mapping were applied to study the effect of magnetoelasticinteractions on the structural perfection and diffraction propertiesof magnetically ordered iron borate crystals. It was established thatthe presence of magnetic domains with different orientation of magnetizationand near-surface magnetism effect in FeBO3 leads to theappearance of disordered areas in crystals and slight changes in thelattice parameters. This is affected in the broadening or splittingof the reciprocal lattice point and diffraction properties of thecrystal. An applied weak external magnetic field alters the domainstructure and significantly improves the diffraction characteristicsof FeBO3 crystals. This effect is important for practicalapplications of iron borate crystals, including the use of these crystalsas X-ray modulators. Itwas established that the presence of magnetic domainsand near-surface magnetism effect in FeBO3 leads to theappearance of disordered areas in crystals and slight changes in thelattice parameters. This is affected in the broadening or splittingof the reciprocal lattice point and diffraction properties of thecrystal. An applied weak external magnetic field alters the domainstructure and significantly improves the diffraction characteristicsof FeBO3 crystals.

A combination of high-resolution X-ray diffraction and X-ray diffraction topography was used for analysis and visualization of elastic strain in ferroelectric triglycine sulfate (TGS) single crystals under uniaxial compression. Diffraction peaks and topographs were obtained for both the 400 and 060 reflections of TGS in transmission geometry under gradually increased compression stress up to 3.5 MPa applied along the [100] and [010] crystallographic directions. All the diffraction data from the sample were obtained from the whole crystal volume with wide beam illumination. Analysis of diffraction patterns revealed a nonlinear increase in integral intensity versus stress and a linear increase in peak broadening versus stress for all compression measurement combinations. The topographs confirmed that the formation of uniform and non-uniform strain fields depended on the direction of crystal compression and its relationship with integral intensity. A twinning process was found for the in-plane reflection along the [100] direction. All the effects induced by compression were reversible after decompression of the sample. According to the results, a significant anisotropy of deformation processes depending on the crystallographic direction was observed, which can be explained by the proposed deformation mechanism with superposition of compression stress, the piezoelectric effect and ferroelectric domain evolution.

An in situ study of the spatial distribution of the piezoelectric properties of an LiNb (1− x ) Ta x O 3 crystal (〈 x 〉 = 0.088) in an external DC electric field was performed by the method of X-ray diffraction of synchrotron radiation at angles close to 180°. The variation of the d 22 piezoelectric coefficient was determined with high accuracy (up to 2%) in local areas by the angular shift of the diffraction maximum under the action of the electric field ( E = 1582 V mm −1 ) applied on the crystal along the Y axis, during scanning along the X and Z directions. A correlation between the piezoelectric strain amplitude and the concentration of tantalum obtained by X-ray fluorescence mapping has been established.

Using the method of time-resolved X-ray diffractometry in a three-crystal scheme, the lattice deformation of a rubidium biphthalate (C 8 H 5 RbO 4 ) crystal was measured in an external electric field. Under the action of an external pulsed electric field along the [001] polar direction, the piezoelectric moduli d 31 ,d 32 , and d 33 were determined independently using three reflections 400, 070, and 004; the obtaind values are -32.8±0.6, 12.8±0.3, and 21.8±1.2 pC/N, respectively. A good agreement was found between the values of the piezoelectric moduli obtained in this work and the values obtained earlier by the quasi-static method. Keywords: piezoelectric effect, time-resolved X-ray diffractometry, three-crystal diffraction scheme, acid phthalate crystals, external electric field.

A diversity of effects leading to deformation of illuminated crystals has been mentioned. A methodical approach to studying the processes of generation of photoinduced deformations in non-centrosymmetric crystals is proposed based on the application of time-resolved X-ray diffraction techniques. Using the experimental measurements with millisecond time resolution, supplemented by numerical calculations, the contributions of piezophotovoltaic and pyroelectric effects, thermal expansion, and optical rectification to the general picture of crystal deformation under illumination are separated. The key parameters of the described deformation contributions are determined for their effective applications.

Using the method of time-resolved X-ray diffractometry in a three-crystal scheme, the lattice deformation of a rubidium biphthalate (С8H5RbO4) crystal was measured in an external electric field. Under the action of an external pulsed electric field along the [001] polar direction, the piezoelectric moduli d31, d32, and d33 were determined independently using three reflections 400, 070, and 004; the obtaind values are –32.8 ± 0.6, 12.8 ± 0.3, and 21.8 ± 1.2 pC/N, respectively. A good agreement was found between the values of the piezoelectric moduli obtained in this work and the values obtained earlier by the quasi-static method.

This work focuses on the validation of a possible connection of the known Ruddlesden-Popper (RP) phases and the novel concept of the migration-induced field-stabilized polar (MFP) phase. To study this subject, model structures of RP phases in bulk strontium titanate are analyzed by means of density functional theory (DFT). The obtained geometries are compared to experimental MFP data. Good agreement can be found concerning atomic displacements in the pm range and lattice strain inferred by the RP phases. Looking at the energy point of view, the defect structures are on the convex hull of the Gibb's free energy. Although the dynamics to form the discussed defect models are not addressed in detail, the interplay and stability of the described defect model will add to the possible structure scenarios within the near-surface region of strontium titanate. As a result, it can be suggested that RP phases generally favor the MFP formation.

The changes in the defect structure in the near-surface layers of lithium tetraborate (Li2B4O7) single crystals under the influence of an external electric field applied along the polar direction [001] have been studied. Using the X-ray diffractometry with 2 ms time resolution the dynamics of the 004 and 008 diffraction peak parameters (the angular position and the integral intensity) variation was determined. Two types of processes caused by the redistribution of the charge localized at the surface of the polar dielectric and by the migration of lithium ions have been observed with different velocity and response time to the external field switching. The measurements are carried out at voltages at which the induced effects have reversible characters. The use of two orders of diffraction with different X-ray extinction lengths made it possible to visualize space charge layers near the anode and cathode by the intensity variation of the diffraction peaks. The estimation of the effective thickness of the charged near-surface layer gives the value of 25 μm for lithium ions at the cathode and about 45 μm for lithium vacancies at the anode.

Paratellurite TeO 2 crystals under the application of a strong electric field demonstrate significant changes of the shape of allowed reflections, which are associated with the migration of oxygen vacancies to the surface layers [1]. Similar effect was found earlier in strontium titanate SrTiO 3 and got the name of “migration-induced field-stabilized polar phase” [2]. An experiment was carried out at P23 beamline of PETRA III synchrotron, devoted to the study of the changes in the forbidden reflections 002 and 100 in TeO 2 under applied electric field. These reflections are forbidden in conventional X-ray scattering, but can be observed at the energies close to absorption L-edges of Te, due to appearance of dipole-dipole resonant contribution to the atomic factor of Te. The experiment was carried out at the incident radiation energy, close to L 1 edge of Te 4938 eV. For both reflections the azimuthal dependence and energy spectrum were measured with and without application of electric field. For 002 reflection electric field magnitude was 500 and 750 V/mm, for 100 reflection it was 750 and 1050 V/mm. We have observed a change of azimuthal dependence (Fig.1) caused by the violation of a symmetry in electric field in accordance with the predictions of preliminary theoretical calculations. Also we have observed a change of the energy spectrum at the magnitude It is assumed that this change is caused by appearance of oxygen vacancies in the environment of Te. For reflection this change of the energy spectrum was even more obvious. is justified because in this experimental geometry migration of is

Currently, a significant area of materials science concerns the development of mechanisms for controlled variation of a material's structure through local defects formation.This ensures the adjustment of a material's structural organization and functional properties for application in novel data storages, sensors, and energy accumulation systems, among others.

Active research in the field of condensed matter and nanotechnology not only led to significant progress in understanding the mechanisms of formation of electrical polarization and magnetoelectric phenomena, but also showed the possibilities of creating new classes of devices based on a combination of magnetoelectric and piezoelectric properties. Meanwhile, macroscopic properties, such as multiferroism and piezoelectricity, are associated with local structural changes that occur under the influence of external perturbations. In a first step chosen crystal structures are analyzed by means of density functional theory (DFT) to validate the connection of external stress and internal change of lattice symmetry as well as atomic displacements. Among them are TeO 2 , Li 2 B4O 7 , ZnO and SrTiO 3 . Also in focus is the influence of oxygen vacancies on our structures. The research is currently accompanied by experiments in which standing acoustic waves are encoupled in crystal samples to change the structure parameters and particularly the structures' symmetry locally. Because the displacements are expected to be on the picometer scale, X-ray diffraction on forbidden reflections is applied to observe the induced effects. The obtained switching results can significantly widen the range of functional materials and can be directly used in modern technological applications.

Multiple‐wave X‐ray reflections usually aggravate the measurement of Bragg reflections, especially of weak “forbidden” reflections. Accurate analysis of multiple‐wave peaks usually allows to avoid this. However, multiple‐wave reflections can also provide information about crystal structure, since crystal cell parameters determine the positions of multi‐wave peaks. The forbidden reflections 002 and 100 in paratellurite are measured and an approach based on semi‐kinematical X‐ray scattering used to handle the multiple‐wave interferences is shown here.

A series of Fe1-xGaxBO3 single crystals was grown by the flux technique. The atomic structure of crystals has been investigated by high-resolution electron microscopy. Crystal structure perfection of the crystals with 0 <= x <= 1 was studied by X-ray diffraction and X-ray topography, and structural defects were visualized. Comparison of the experimental and calculated data for crystals of the extreme members of the series FeBO3 and GaBO3 with the crystals of solid solutions Fe1-xGaxBO3 revealed a slight decrease in the structural perfection of "mixed" crystals where partial isomorphic substitution of iron for gallium occurs. Along with this, each of the studied samples contains regions free of defects and stresses. The results of this work have demonstrated the possibility of using Fe1-xGaxBO3 crystals as monochromators in synchrotron experiments based on nuclear resonances. (C) 2021 Elsevier B.V. All rights reserved.