Reliable electrical contacts are essential for high-temperature piezoelectric devices based on lithium niobate (LiNbO3, LN), yet the behavior of electrode materials under elevated temperatures remains insufficiently studied. Here we evaluate three practical electrode systems on bidomain LN (BLN) substrates: screen-printed Pd thick films, sputtered indium–tin oxide (ITO), and sputtered nichrome (80 wt.% Ni and 20 wt.% Cr). Bidomain LN crystals function as single-crystal piezoelectric bimorphs with well-defined bending resonances, enabling sensitive impedance-based detection of electrode degradation. Impedance spectra were recorded in 100 °C increments up to 800 °C, complemented by microstructural inspection, electrical resistivity measurements, and X-ray photoelectron spectroscopy. Pd thick films showed the highest stability, with unchanged impedance spectra after heating to 800 °C and cooling. Indium–tin oxide electrodes remained functional up to at least 700 °C, with possible operation at 800 °C. X-ray photoelectron spectroscopy results suggest gradual incorporation of Nb from the BLN substrate which may initiate slow degradation in ITO. NiCr electrodes showed degradation of electrical contact near 500 °C due to oxide formation, while intrinsic electrical degradation associated with loss of film continuity occurred above 600 °C. These results identify Pd as a robust but costly choice, ITO as a promising mid-range alternative, and NiCr as suitable only within a lower high-temperature window.

Rapid adjustment of X-ray optics is crucial for time-resolved studies that track dynamic material processes in real time. Conventional servo- or stepper-driven goniometers are too slow, prompting interest in piezo-actuated adaptive X-ray optical elements (AXOEs). A piezoelectric bimorph in an AXOE can sweep the beam by hundreds to thousands of arcseconds at several-hundred-hertz rates. Although single-crystal AXOE monochromators outperform mechanical stages, only double-crystal geometries preserve beam direction during energy scans and suppress angular divergence. Synchronizing two crystals, however, is difficult with standard PbZrxTi1-xO3 (PZT) bimorphs, whose hysteresis and thermal drift degrade reproducibility. We report a double-crystal monochromator that employs two adaptive bending X-ray optical elements (ABXOs) based on bidomain LiNbO3 (BLN) single-crystal bimorph actuators. The monolithic structure of BLN eliminates intergrain interfaces, yielding hysteresis-free response and high thermal stability. Two mechanically matched actuators, each resonant at approximate to 102.5 Hz with mirrors attached, deliver angular sweeps exceeding 1200 arcsec. We describe calibration and phase-synchronization procedures that provide traceable control of beam energy and alignment. Performance was verified at the Kurchatov Synchrotron Source. Measurements confirmed the predicted angular and spectral tuning ranges and quantified beam displacement. Using the prototype, we recorded the Cu K-edge absorption spectrum (similar to 20 mu m foil) with markedly higher spectral resolution than a comparable single-crystal ABXO system. These results demonstrate that BLN-based ABXOs enable fast, reproducible, and direction-stable energy scanning for synchrotron diffraction and spectroscopy, opening a path toward sub-10 ms time resolution without complex feedback hardware.

The study demonstrates that the dynamic characteristics of piezoelectric bimorph actuators based on bidomain lithium niobate (BLN) single crystals are accurately described by an analytical one-dimensional (1D) model of an ideal bimorph. Our observations show that displacements and an electric impedance of the BLN-based bimorphs can be predicted without use of any sophisticated lumped circuit models, equations with handpicked "effective" values of material's constants or finite element method. The experimental data were measured by means of laser interferometry and impedance spectroscopy and then fitted with the equations predicted by the 1D model. Solving the inverse problem for the experimental points we calculated the transverse piezoelectric coefficient, longitudinal mechanical compliance, dielectric permittivity, and piezoelectric coupling coefficient of the material. The obtained values of the material constants of the lithium niobate y + 128 degrees-cut crystal are d23 = 25 pC/N, sE33 = 7.58 TPa-1, 8T22 = 52.7 80, and k223 = 0.18, which are in excellent agreement with the literature data.

Magnetoelectric (ME) composites are extensively researched for their ability to detect magnetic fields but are typically characterized by their interactions with homogeneous magnetic fields. However, practical applications often involve non-uniform magnetic fields (NMFs). In this study, we developed and validated a technique for 2D mapping of NMFs using sensor based on ME composite. The primary focus was on mapping the magnetic field generated by a single wire carrying an alternating current (AC). The experimental setup included a "bidomain LiNbO3/Ni/Metglas" ME structure, which demonstrated a ME coefficient of 0.83 V/(cm & sdot;Oe) without external biasing at 117 Hz. The ME structure was characterized using both quasi-static and dynamic methods, with the mapping performed at a frequency of 232 Hz, chosen to ensure a linear response and minimize resonance effects. Our measurements revealed that the position of maximum magnitude of the ME signal was consistently shifted from the position of the maximum integral magnetic field intensity of the wire. This shift was attributed to the deformation of the ME structure and the redistribution of the magnetic flux along the sample due to the magnetic layers, as confirmed through modeling. Further, the measured 2D mapping of the NMF from the wire closely matched the theoretical distribution, displaying axial symmetry but with a persistent shift of 2-3 mm along the length of the ME structure. These effects were linked to the linear dimensions and clamping methods of the ME structure. Overall, our experimental results closely correlated with theoretical data and the FEM model, demonstrating that ME composites are effective for NMF detection and mapping. Future work will aim to reduce the dimensions of the ME structure using MEMS technology to minimize the observed shift effects in the measurements.

Charged domain walls (CDWs) in ferroelectrics exhibit enhanced and tunable conductivity, making them attractive for devices such as non-volatile memories, memristors, and hybrid electro-optic-mechanical systems. Most previous studies of CDWs in lithium niobate (LiNbO 3 ) have focused on Mg-doped crystals. Here, we investigate an extended head-to-head CDW with an inclination angle close to 90°, formed in nominally pure congruent LiNbO 3 during high-temperature reduction annealing near the Curie point. The electrophysical properties of such reduced bidomain crystals, where the bulk shows mixed free- and bound-polaron transport, remain largely unexplored. We systematically measured temperature-dependent current–voltage characteristics from room temperature up to 60 °C using planar structure with Ti electrodes. Data were acquired separately on electrodes contacting the single-domain bulk and those intersecting the CDW (where the measured current is a sum of the CDW and the surrounding single-domain conductivity). Applying the R2D2 equivalent-circuit model enabled us to isolate the intrinsic conductivity of the CDW itself from the parallel conduction channel of the adjacent single-domain matrix. The analysis revealed a stark contrast in activation energies. In the bulk, it was ≈0.5 eV, attributed to bound-polaron hopping. At the CDW, however, the activation energy was not only significantly lower but also exhibited a pronounced polarity dependence: 0.13 eV for one voltage bias and 0.20 eV for the opposite polarity. This anisotropy and the suppression of the activation energy are consistent with a high-density free-polaron gas near the wall, where strong mutual repulsion between carriers reduces the energy barrier for charge transport. Independent determination of currents and activation energies for bulk and domain walls provides new insight into charge-transport mechanisms in ferroelectrics and highlights the potential of domain-wall engineering for future nanoelectronics applications.

Charged domain walls (CDWs) in ferroelectric materials are of interest from both fundamental and applied perspectives due to their unique electrophysical properties, which differ significantly from those of the bulk material. Until recently, research efforts primarily focused on studying these properties, while less attention was given to the finite-thickness regions of CDWs with heterogeneous electrical conductivity. This study proposes a model describing the charge carrier distribution within the conductive region of CDWs. The dependencies of charge carrier concentration and mobility on the distance from the CDW were determined. An analytical expression for current-voltage characteristics, measurable by conductive atomic force microscopy (c-AFM), was also proposed. The model has been experimentally validated using AFM methods. In particular, the Debye screening length of the electric field of head-to-head (H–H) CDWs by free charge carriers in strongly reduced LiNbO3 crystals was found to be 90±10 nm. Additionally, the values of mobility and concentration of polarons forming the conductive H–H CDW were determined. The bound polaron concentration in this region is estimated to be approximately 30 times greater than in the monodomain region, reaching ≈3.8·1017 cm-3.

This study examines the bending dynamics of cantilevered single-crystalline bimorphs made from bidomain LiNbO3 (BLN), emphasizing the interaction between bending resonances, antiresonances, and torsional vibrations. Combining theoretical modeling and experimental validation, we demonstrate that a 1D analytical model, based on classical beam theory, surpasses FEM modeling in predicting bending resonances, particularly in the low-frequency range. The analytical model provides precise positioning of resonant frequencies, enabling the strategic alignment of torsional resonances with bending antiresonances, as confirmed experimentally. Our findings underscore the high predictability of BLN-based bimorphs, allowing accurate descriptions of their behavior at bending resonances, antiresonances, and piezoelectrically passive torsional resonances. Unlike glued actuators made of lead-based ceramics, BLN bimorphs offer superior thermal stability, long-term reliability, and predictable performance. These properties, combined with the availability of commercially produced LN crystals, position BLN-based bimorphs as ideal candidates for MEMS applications, enabling advanced sensing and actuation solutions with reduced reliance on complex feedback loops.

Charged domain walls (CDWs) in ferroelectric materials raise both fundamental and practical interest due to their electrophysical properties differing from bulk ones. On a microstructure level, CDWs in ferroelectrics are 2D defects separating regions with different spontaneous polarization vector directions. Screening of electric field of the CDW's bound ionic charges by mobile carriers leads to the formation of elongated narrow channels with an elevated conductivity in initially dielectric materials. Controlling the position and inclination angle of CDW relative to the spontaneous polarization direction, one can change its conductivity over a wide range thus providing good opportunities for developing memory devices, including neuromorphic systems. This review describes the state of art in the formation and application of CDWs in single crystal uniaxial ferroelectric lithium niobate (LiNbO3, LN), as resistive and memristive switching devices. The main CDWs formation methods in single crystal and thin-film LN have been described, and modern data have been presented on the electrophysical properties and electrical conductivity control methods of CDWs. Prospects of CDWs application in resistive and memristive switching memory devices have been discussed.

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.

Magnetoelectric (ME) composites have a wide range of possible applications, especially as room-temperature sensors of weak magnetic fields in magnetocardiography and magnetoencephalography medical diagnostic equipment. In most works on ME composites, structures are tested in uniform magnetic fields; however, for practical application, detailed knowledge of their behaviour in inhomogeneous magnetic fields (IMFs) is necessary. In this work, we measured IMFs with radial symmetry produced by alternate currents (AC) passing through an individual thin wire upon different placements of an ME sensor. An ME self-biased b-LN/Ni/Metglas structure with a sensitivity to the magnetic field of 120 V/T was created for IMF detection. The necessity of an external biasing magnetic field was avoided by the inclusion of a nickel layer having remanent magnetization. The ME composite shows a non-zero ME coefficient of 0.24 V/(cm · Oe) in the absence of an external DC magnetic field. It is shown that the output voltage amplitude from the ME composite, which is located in an AC IMF, is dependent on the relative position of the investigated sample and magnetic field lines. Maximum ME signal is obtained when the long side of the ME sample is perpendicular to the wire, and the symmetry plane which divides the long side into two similar pieces contains the wire axis. In the frequency range from 400 Hz to 1000 Hz in the absence of vibrational and other noises, the detection limit amounts to (2 ± 0.4) nT/Hz1/2.

Silicon-carbon films are of great interest as diamond-like materials combining unique properties, e.g. high hardness, adhesion to a wide range of materials, abrasion resistance, chemical resistance, low friction coefficient and biocompatibility. The presence of silicon in the films significantly reduces their inner mechanical stress as compared to diamond films. Currently, the films are used in industry, primarily, as solid lubricants and protective coatings. There are a large number of silicon-carbon film synthesis methods the most widely used of which are various options of chemical vapor deposition. A new silicon-carbon film synthesis technique has been suggested and tested. The technique is based on the use of high-frequency induction for obtaining plasma of silicon and carbon vapors supplied to the reaction chamber from an external source. Impurity-free silicon-carbon films containing 63–65 % carbon atoms with sp3 orbital hybridization have been synthesized on Sitall substrates. The composition, surface roughness and friction coefficient of the impurity-free silicon-carbon films synthesized using the suggested technology have been studied. The possibility of implementing resistive switching in thin silicon-carbon films in cross-bar structures with metallic electrodes has been analyzed.

In this work the effect of annealing in a constant magnetic field on the magnetoelectric (ME) coefficient in three-layered gradient composites is investigated. A technique of nickel electrochemical deposition on bidomain lithium niobate crystals was demonstrated. It is shown that the optimum temperature for the formation of the maximum remanent magnetization of the Ni layer in a constant magnetic field is 350 °C. In the samples annealed at this temperature, the maximum shift of the dependence of the ME coefficient on the external constant magnetic field relative to the value of 0 Oe was achieved. Quasistatic ME coefficient value was 1.2 V/(cm∙Oe) without applying of external DC magnetic field. The maximum value of the ME coefficient was reached 199.3 V/(cm∙Oe) at bending resonance of 278 Hz without external DC magnetic field. Obtained in this work values of ME coefficients don’t yield to most of ME composite materials which were published before.

Non-contact mapping of magnetic fields produced by the human heart muscle requires the application of arrays of miniature and highly sensitive magnetic field sensors. In this article, we describe a MEMS technology of laminated magnetoelectric heterostructures comprising a thin piezoelectric lithium niobate single crystal and a film of magnetostrictive metglas. In the former, a ferroelectric bidomain structure is created using a technique developed by the authors. A cantilever is formed by microblasting inside the lithium niobate crystal. Metglas layers are deposited by magnetron sputtering. The quality of the metglas layers was assessed by XPS depth profiling and TEM. Detailed measurements of the magnetoelectric effect in the quasistatic and dynamic modes were performed. The magnetoelectric coefficient |α32| reaches a value of 492 V/(cm·Oe) at bending resonance. The quality factor of the structure was Q = 520. The average phase amounted to 93.4° ± 2.7° for the magnetic field amplitude ranging from 12 to 100 pT. An AC magnetic field detection limit of 12 pT at a resonance frequency of 3065 Hz was achieved which exceeds by a factor of 5 the best value for magnetoelectric MEMS lead-free composites reported in the literature. The noise level of the magnetoelectric signal was 0.47 µV/Hz1/2. Ways to improve the sensitivity of the developed sensors to the magnetic field for biomedical applications are indicated.

Temperature and magnetic field dependencies of sheet resistance R # (T,B) in polycrystalline CVD graphene, investigated in the range of 2≤ T≤ 300 K and magnetic fields 0≤ B≤ 8 T, allowed to determine carrier transport mechanisms in single-layered and twisted CVD graphene. It is shown that for R # (T,B) curves for such samples are described by the interference quantum corrections to the Drude conductivity independently on type of precursor and peculiarities of graphene transfer from Cu foil onto the various substrates (glass or SiO 2 ). The twisted CVD graphene samples have demonstrated additional contribution of 2D hopping conductivity into the R # (T,B) dependencies. Keywords: graphene, single layer, twisted layers, CVD, carrier transport, magnetoresistance.

Lithium niobate (LiNbO3) and lithium tantalate (LiTaO3) are among the most important and most widely used materials of coherent and nonlinear optics, as well as acoustics. High degree of uniformity and reproducibility has become the foundation of technology for manufacturing high-quality crystals, absorbed by many suppliers around the world. However, the above areas do not limit the use of LiNbO3 and LiTaO3 due to their unique piezoelectric and ferroelectric properties. One promising application of crystals is the design of electromechanical transducers for precision sensors and actuators. In this respect, the high thermal stability of the piezoelectric and mechanical properties, the lack of hysteresis and creep make it possible to create electromechanical converters with wide operating temperature range, that is beyond the capability of commonly used ferroelectric ceramics. The main advantage of LiNbO3 and LiTaO3 over other single-crystal piezoelectrics is ferroelectric domain structure regulation toward targeted impact on the device characteristics. One of the most striking examples of electromechanical transducer design through domain engineering is the formation of a so-called bidomain ferroelectric structure in crystal. It represents a single-crystalline plate with two macrodomains with opposite directions of spontaneous polarization vectors separated by a charged domain wall. High switching fields make inversion domains stable at temperatures up to 1000 °C. This review summarizes the main achievements in the formation of bidomain structure and near surface inversion domains in LiNbO3 and LiTaO3 crystals. We present the domain structure virtualization methods in crystals and non-destructive methods for controlling the domain boundary position. The report contains a comparative analysis of the methods for forming inversion domains in crystals, and the patterns and technological control methods of the domain structure are discussed. The basic physical models have been proposed in the literature to explain the effect of the inversion domains formation. In the present paper we outline what one sees as strengths and weaknesses of these models. The strategies of crystallographic cut selection to create devices based on bidomain crystals are briefly discussed. We provide examples of the implementation of devices based on bidomain crystals such as actuators, sensors, acoustic transducers, and waste energy collection systems.

In this work, the effect of long-term room temperature exposure on the electrical conductivity of the charged domain wall (CDWs) in nonpolar x-cut congruent lithium niobate (LiNbO3, LN) crystals has been studied. Bidomain ferroelectric structures containing head-to-head charged domain boundaries have been produced by diffusion annealing in air near the Curie temperature and by infrared annealing. The crystals have been reduction annealed in a nitrogen atmosphere for the formation of color centers and growth of the electrical conductivity. The current measured during the recording of the I-V curves of the specimens using scanning probe microscope after room temperature exposure for 91 days has been found to decrease. The effect of storage conditions on the electrical conductivity of the CDWs has been studied. Degradation of the electrical conductivity does not originate from the effect of environment on the crystal surface. It has been hypothesized that the degradation is caused by distribution of charge carriers shielding the bound charge of the CDWs.

Composite multiferroics are materials in which electric polarization of the material is possible under the action of an external magnetic field and vice versa, a change in the magnetization of the structure when an electric field is applied. Such properties have a high practical potential for application in science and technology. Based on these materials, it is possible to manufacture a number of devices with unique properties, such as, for example, random access magnetoelectric (ME) memory, ME sensors of magnetic fields, current, magnetic nanoparticles, micromechanical ME antennas, voltage-adjustable microwave filters, resonators and phase shifters. Therefore, the search for new materials of composite multiferroics and the study of the ME effect in them is a priority and urgent task in the search and creation of new electronic devices. One of the most promising and close to practical implementation directions is the creation of highly sensitive sensors of ultra-weak magnetic fields on the basis of composite multiferroics. The absence of the need to cool such sensors is a significant technical advantage over superconducting quantum interferometers currently used for these purposes. To date, the best achieved limits for detecting magnetic fields using sensors based on composite magnetoelectrics are values of the order of pT/Hz(1/2), and new works are regularly published that reduce this threshold by improving processing electronics and changing the sensor design. This threshold of sensitivity is already sufficient for reliable detection of magnetic fields induced by alpha-rhythm currents of the brain with amplitudes of units of pT (magnetoencephalography) and for detecting the magnetic activity of the human heart. The review article is devoted to composite magnetoelectric structures with a focus on sensor structures capable of detecting ultra-weak magnetic fields. The comparison of the limiting sensitivity to the magnetic field of the existing ME composite structures is carried out, the ways of increasing the sensitivity to the magnetic field are shown.

The effect of annealing in a permanent magnetic field on the magnitude of magnetoelectric coefficient in three-layered gradient magnetoelectric LiNbO3/Ni/Metglas composites has been studied. A method of electrochemical nickel deposition on bidomain lithium niobate crystals has been demonstrated. We show that the optimum annealing temperature in a permanent magnetic field for the generation of the highest remanence in the Ni layer is 350 °C. The specimens annealed at this temperature exhibit the greatest shift of the magnetoelectric coefficient dependence on external magnetic field magnitude relative to the value Hdc = 0. The quasi-static magnetoelectric coefficient in the absence of an external magnetic field proves to be 1.2 V/(cm ∙ Oe). The highest magnetoelectric coefficient that has been achieved at a bending structure resonance frequency of 278 Hz proves to be 199.3 V/(cm ∙ Oe) without application of an external magnetic field. The experimental magnetoelectric coefficient figures for three-layered gradient LiNbO3/Ni/Metglas composites are not inferior to those for most magnetoelectric composite materials reported earlier.

Lithium niobate is a ferroelectric material finding a wide range of applications in optical and acoustic engineering. Annealing of lithium niobate crystals in an oxygen-free environment leads to appearance of black coloration and concomitant increasing electrical conductivity due to chemical reduction. There are plenty of literary data on the electrophysical properties of reduced lithium niobate crystals though contact phenomena occurring during electrical conductivity measurement as well as issues of interaction between the electrode material and the test specimens are almost disregarded. The effect of chromium and indium tin oxide electrodes on the results of measurements of electrophysical parameters at room temperature for lithium niobate specimens reduced at 1100 °C has been investigated. It was found that significant nonlinearities in the VACs of the specimens at below 5 V distort the specific resistivity readings for lithium niobate. This requires measurements at higher voltages. Impedance spectroscopy studies have shown that the measurement results are largely affected by capacities including those probably induced near the contacts. It has been shown that the experimental results are described adequately well by a model implying the presence of near-contact capacities that are parallel to the specimen’s own capacity. Possible mechanism of the induction of these capacities has been described and a hypothesis has been proposed of the high density of electron states at the electrode/specimen interface that can trap carriers, the concentration of trapped carriers growing with an increase in annealing duration.