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Owing to the complex composition architecture of these solid solutions, some fundamental issues of the classical (1−x)Bi1/2Na1/2TiO-xBi1/2K1/2TiO3 (BNT-xBKT) binary system, such as details of phase evolution and optimal Na/K ratio associated with the highest strain responses, remain unresolved. In this work, we systematically investigated the phase evolution of the BNT-xBKT binary solid solution with x ranging from 0.12 to 0.24 using not only routine X-ray diffraction and weak-signal dielectric characterization, but also temperature-dependent polarization versus electric field (P-E) and current versus electric field (I-E) curves. Our results indicate an optimal Na/K ratio of 81/19 based on high-field polarization and electrostrain characterizations. As the temperature increased above 100 °C, the x = 0.19 composition produces ultrahigh electrostrains (> 0.5%) with high thermal stability. The ultrahigh and stable electrostrains were primarily due to the combined effect of electric-field-induced relaxor-to-ferroelectric phase transition and ferroelectric-to-relaxor diffuse phase transition during heating. More specifically, we revealed the relationship between phase evolution and electrostrain responses based on the characteristic temperatures determined by both weak-field dielectric and high-field ferroelectric/electromechanical property characterizations. This work not only clarifies the phase evolution in BNT-xBKT binary solid solution, but also paves the way for future strain enhancement through doping strategies. © 2021 The Chinese Ceramic Society.

Charge carrier transport through the probe-sample junction can have substantial consequences for outcomes of electrical and electromechanical atomic-force-microscopy (AFM) measurements. For understanding physical processes under the probe, we carried out conductive-AFM (C-AFM) measurements of local current-voltage (I-V) curves as well as their derivatives on samples of a mixed ionic-electronic conductor Li1-xMn2O4 and developed an analytical framework for the data analysis. The implemented approach discriminates between contributions the highly resistive sample surface layer and the bulk with the account of ion redistribution in the field of the probe. It was found that, with increasing probe voltage, the conductance mechanism in the surface layer transforms from Pool-Frenkel to space-charge-limited current. The surface layer significantly alters the ion dynamics in the sample bulk under the probe, which leads, in particular, to a decrease of the effective electromechanical AFM signal associated with the ionic motion in the sample. The framework can be applied for the analysis of electronic transport mechanisms across the probe/sample interface as well as to uncover the role of the charge transport in the electric field distribution, mechanical, and other responses in AFM measurements of a broad spectrum of conducting materials. © 2020 Elsevier B.V.

Samarium substituted bismuth ferrite (BiFeO3) ceramics prepared by sol-gel synthesis method were studied using both local scale and microscopic measurement techniques in order to clarify an evolution of the crystal structure of the compounds across the morphotropic phase boundary region. X-ray diffraction analysis, transmission and scanning electron microscopies, XPS, EDS/EDX experiments and piezoresponse force microscopy were used to study the structural transitions from the polar active rhombohedral phase to the anti-polar orthorhombic phase and then to the non-polar orthorhombic phase, observed in the Bi1−xSmxFeO3 compounds within the concentration range of 0.08 ≤ x ≤ 0.2. The results obtained by microscopic techniques testify that the compounds in the range of 0.12 ≤ x ≤ 0.15 are characterized by two phase structural state formed by a coexistence of the rhombohedral and the anti-polar orthorhombic phases; two phase structural state observed in the compounds with 0.15

A diffractive optical element based on a nonlinear-optical ferroelectric single crystal has been proposed, synthesized, and experimentally characterized. The element allows fast modulation of transverse modes of a Gaussian laser beam. © 2021, Institution of Russian Academy of Sciences. All rights reserved.

Forward domain growth representing one of the main stages of domain switching is studied for isolated domains and domain arrays appearing as a result of tip-induced switching on the non-polar cuts of lithium niobate crystals. Formation of the wedge-like domains with a high aspect ratio and charged domain walls is observed. The domain growth in the area with a negligible external field is considered in terms of the kinetic approach based on analogy with crystal growth. The domain wall motion by step generation and propagation of the charged kinks is discussed. It is proposed that the switching field contains the inputs of the external field produced by a biased scanning probe microscope tip, the depolarization field produced by charged kinks, and the screening fields. According to the simulation results of the field distribution, the forward growth is caused by the step generation near the tip and the kink propagation induced by the depolarization field produced by the kinks. Scanning with the biased tip creates self-assembled domain arrays with several modes of domain length alteration: doubling, quadrupling, and chaotic. The statistical characterization of the arrays proves their high ordering. The array is formed under the influence of the depolarization field produced by three neighboring domains. The proposed mechanism can be applied for forward domain growth during switching on the polar cuts as well. In this case, the steps on the domain wall are generated on the polar surface, whereas the domain elongates by kink motion in the field produced by the charged kinks. © 2021 Author(s).

In vitro toxicological experiments were performed on an endothelial cell line exposed to different doses of spherical nanoparticles of cadmium and/or of lead sulfides with mean diameter 37 ± 5 nm and 24 ± 4 nm, respectively. Toxic effects were estimated by Luminescent Cell Viability Assay, endothelin-1 concentration and cell size determination. Some dose-response relationships were typically monotonic (well approximated with hyperbolic function) while others were bi- or even 3-phasic and could be described within the expanded hormesis paradigm. The combined toxicity type variated depending on the effect it was assessed by. © The Author(s) 2021.

The method of Fe3O4 magnetic nanoparticle synthesis by co-precipitation, modification by 3-aminopropylsilane and conjugation with pH-(low)-insertion peptide (pHLIP) is reported. The characterization of nanoparticles by scanning electron microscopy, transmission electron microscopy, Fourier-transform infrared spectroscopy, elemental and thermogravimetric analyses as well as dynamic light scattering and z-potential measurements is provided. The effect of nanoparticles on the viability of mouse and human peripheral blood mononuclear cells is tested by flow cytometry. The experimental details of nanoparticle administration to tumor-bearing mice, magnetic resonance imaging scanning as well as subsequent tumor sample collection and their processing for transmission electron microscopy, inductively coupled plasma atomic emission spectroscopy, histological and immunohistochemical analyses are described. Biodistribution of the nanoparticles in mice and blood serum analysis data for experimental animals are given. The data are useful for an experiment workflow design and for the development of theranostic systems based on magnetic nanoparticles. © 2020 The Authors

Outbred female rats were exposed to inhalation of lead oxide nanoparticle aerosol produced right then and there at a concentration of 1.30 ± 0.10 mg/m3 during 5 days for 4 h a day in a nose-only setup. A control group of rats were sham-exposed in parallel under similar conditions. Even this short-time exposure of a relatively low level was associated with nanoparticles retention demonstrable by transmission electron microscopy in the lungs and the olfactory brain. Some impairments were found in the organism’s status in the exposed group, some of which might be considered lead-specific toxicological outcomes (in particular, increase in reticulocytes proportion, in δ-aminolevulinic acid (δ-ALA) urine excretion, and the arterial hypertension’s development). © 2020 by the authors. Licensee MDPI, Basel, Switzerland.

Ferroelectric materials based on lead zirconate titanate (PZT) are widely used as sensors and actuators because of their strong piezoelectric activity. However, their application is limited because of the high processing temperature, brittleness, lack of conformal deposition, and a limited possibility to be integrated with the microelectromechanical systems (MEMS). Recent studies on the piezoelectricity in the 2-D materials have demonstrated their potential in these applications, essentially due to their flexibility and integrability with the MEMS. In this work, we deposited a few layer graphene (FLG) on the amorphous oxidized Si3N4 membranes and studied their piezoelectric response by sensitive laser interferometry and rigorous finite-element modeling (FEM) analysis. Modal analysis by FEM and comparison with the experimental results show that the driving force for the piezoelectric-like response can be a polar interface layer formed between the residual oxygen in Si3N4 and the FLG. The response was about 14 nm/V at resonance and could be further enhanced by adjusting the geometry of the device. These phenomena are fully consistent with the earlier piezoresponse force microscopy (PFM) observations of the piezoelectricity of the graphene on SiO2 and open up an avenue for using graphene-coated structures in the MEMS. © 1986-2012 IEEE.

The creation of the periodical domain patterns with a submicron period in lithium niobate on insulator (LNOI) wafers is a key problem for nonlinear-optical applications, including second harmonic generation, backscattering optical parametric oscillator, etc. We have experimentally studied the domain formation and evolution during local polarization reversal in Z+ LNOI wafers with a metal bottom electrode. It has been shown that domain growth occurs by the formation of the spikes at the charged domain wall (CDW). The complicated shape of isolated domains with a jagged CDW has been revealed. The obtained weak domain-domain interaction has been attributed to effective bulk screening by charge injection. The revealed dependence of the domain sizes on humidity caused by the adsorbed water layer should be taken into account during periodical poling. © 2020 Author(s).

The domain switching by ion beam irradiation of single-domain Y-cut plates of congruent lithium niobate doped by 5 mol% MgO was studied. Dot irradiation resulted in the formation of wedge-like domains grown along Z- polar direction. The nonlinear dependences of the domain sizes on irradiation conditions were obtained. The model of domain growth on non-polar cut was proposed in frame of kinetic approach. The absence of the domain merging along Z- polar direction was attributed to the deceleration of the forward growth by electrostatic interaction of the positive charges at the charged domain walls and injected positive ions. © 2020, © 2020 Taylor & Francis Group, LLC.

The formation of the maze domain structures in the plates of congruent lithium niobate single crystal caused by multiple irradiation of infrared pulsed laser at different plate temperatures was studied. Four stages of domain evolution with increasing pulse number were distinguished. The dependence of the formed self-organizing domain structures on pulse number and sample temperature was revealed. Suppression of the domain formation at the elevated temperatures was attributed to increasing ionic conductivity, which led to decreasing the switching field. © Published under licence by IOP Publishing Ltd.

The microstructure and surface morphology of (Ba0.8,Sr0.2)TiO3 based glass-ceramics with different amounts of La and Ce were studied. It was shown that the addition of the 1.5% La and >2%Ce led to formation of dendrite-like structures. The isolated clusters of ferroelectric phase were found in all investigated samples. Fraction of ferroelectric phase was about 0.75% for La addition and 0.25% for Ce addition. © Published under licence by IOP Publishing Ltd.

Production of non-spherical crystalline nanoparticles by laser ablation in liquid has been demonstrated recently. Here we studied the shape variety of PbO nanoparticles prepared by laser ablation in deionized water and IPA. The key role of water in the formation of PbO non-spherical nanostructures was demonstrated. Only spherical nanoparticles have been obtained in isopropyl alcohol (IPA). PbO non-spherical nanostructures have been formed only in presence of water, which supports the growth mechanism by oxidation. Using mixture of IPA and water in various proportions and revealing the time and temperature dependences of non-spherical nanostructure morphology can be used for controlled growth of PbO non-spherical nanostructures. © Published under licence by IOP Publishing Ltd.

The morphology of a single charged domain wall, appeared under the action of composition gradients produced by partial VTE procedure by Cherenkov-type second harmonic generation microscopy, was observed in detail. The width of the charged domain wall was estimated as 70 μm. Non-through and through narrow domains, grown from the charged domain wall, were revealed. The maximum length of non-through domains with submicron diameter was about 100 μm. The growth of narrow domains from the charged domain wall was demonstrated and attributed to the action of pyroelectric field. The widening of domains occurred after achieving the polar surface. © Published under licence by IOP Publishing Ltd.

Nanoparticles of metals and their oxides (Me-NPs) are of special interest in the light of health risks assessment and management, because, along with engineered Me-NPs, there exists usually a substantial fraction of nanoscale ("ultrafine") particles of the same substances within the particle size distribution of condensation aerosols generated by arc-welding, metallurgical, and some chemical technologies. The nonspecific responses of the organism to the impact of Me-NP included: changes in the cytological and some biochemical characteristics of the bronchoalveolar lavage fluid caused by the deposition of particles in the lower airways, various manifestations of systemic toxicity including significant damage to the liver and kidneys, moderate neurological disturbances associated with possible penetration of Me-NP into the brain from the blood as well as from the nasal mucous membrane along the olfactory pathway, a paradoxically low manifestation of pulmonary pathology due to low chronic retention of nanoparticles in the lungs, and a genotoxic effect on the organism level. The toxicity and even genotoxicity of Me-NPs can be significantly attenuated by adequately composed combinations of some bioactive agents in innocuous doses. © Published under licence by IOP Publishing Ltd.

In this report, we present a detailed study of the formation of alumina nanostructures at the surface of aluminium plate by hot water treatment (HWT) at various temperatures. The nanostructures were studied by scanning electron microscopy. The superhydrophilic property of the treated surface was revealed and its stability was investigated. It was shown that HWT could be used also for synthesis of the aqueous suspensions of alumina nanoparticles. It is proposed that the method can be applied for production of surface nanostructures and nanoparticles of various metal oxides. © Published under licence by IOP Publishing Ltd.

Female white rats were exposed during up to 6 months 5 times a week, 4 hr per day in a "nose only" inhalation device to an aerosol containing predominantly submicron (nanoscale included) particles of amorphous silica in the concentration 2.6±0.6 or 10.6±2.1 mg/m3. In an auxiliary experiment with a single-shot intratracheal instillation of these particles, it was shown that they induced a pulmonary cell response comparable with that to highly cytotoxic and fibrogenic standard quartz powder DQ12. However, in the long-term inhalation test, the studied aerosol proved to be of very low systemic toxicity and fibrogenicity. This paradox may be explained by low SiO2 retention in lungs and other organs due to a relatively high in vivo solubility of these nanoparticles. Nevertheless, their genotoxic action and transnasal penetration into the brain should make one give a cautious overall assessment of this aerosol as an occupational or environmental hazard. © Published under licence by IOP Publishing Ltd.

Optical waveguides are fabricated by irradiation of LiTaO 3 with a variety of swift heavy ions that provide increasing levels of both nuclear and electronic damage rates, including C, F and Si ions, in the energy range of 15-40 MeV. A systematic study of the role of the ion fluence has been carried out in the broad range of 1e13-2e15 at/cm 2 . The kinetics of damage is initially of nuclear origin for the lowest fluences and stopping powers and, then, is enhanced by the electronic excitation (for F and Si ions) in synergy with the nuclear damage. Applying suitable annealing treatments, optical propagation losses values as low as 0.1 dB have been achieved. The damage rates found in LiTaO 3 have been compared with those known for the reference LiNbO 3 and discussed in the context of the thermal spike model. © 2019 Optical Society of America.

The features of the domain patterning in thin lithium niobate crystals were studied. It was shown that decrease in crystal plate thickness led to domain size increase due to limitation of forward growth. The domain size weakly depended on electron energy due to equality of screening charge value at the same doses and various accelerating voltages. The weak dependence of domain sizes on pattern period was attributed to absence of electrostatic interaction of domain walls. The possibility of creation of the through periodical domain structures with the vertical domain walls and period down to 2 μm in thin crystal was demonstrated. © 2019, © 2019 Taylor & Francis Group, LLC.

Stress-induced local polarization reversal was studied in La doped BiFeO3 ceramics under the action of Berkovich-type prism indentation. Piezoresponse force microscopy was used for detailed study of domain structure before and after local polarization reversal. Two mechanisms of domain formation under the action of the mechanical loading were revealed: (1) direct stress-induced and (2) stress mediated by grain clamping. Critical stress value for local polarization reversal was extracted from the dependence of the switched area on the applied loading force. © 2019, © 2019 Taylor & Francis Group, LLC.

High purity In2O3 crystals were synthesized by the chemical vapour transport (CVT) as confirmed by X-ray Photoelectron Spectroscopy (XPS) using survey, core-levels and valence band scans of the samples. Further, high energy resolution XPS spectra revealed perfectly bonded In 3d configuration and excluded the presence of metallic In0, concurrently, the dual band observed for O 1s configuration was interpreted in term of the additional defectiveness in the oxygen sublattice. The valence band as measured by XPS is in agreement with the calculated one using DFT approach, and an insignificant shift of valence band toward Fermi level (about 0.05 eV) caused by the presence of the defects was established. Moreover, the energetics of the primarily defects were calculated and the trends were set in the perspective of XPS measurements. Altogether we make CVT In2O3 crystals ready to be used for the onward studies and technical applications. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.

Rats were exposed to nickel oxide nanoparticles (NiO-NP) inhalation at 0.23 ± 0.01 mg/m3 for 4 h a day 5 times a week for up to 10 months. The rat organism responded to this impact with changes in cytological and some biochemical characteristics of the bronchoalveolar lavage fluid along with a paradoxically little pronounced pulmonary pathology associated with a rather low chronic retention of nanoparticles in the lungs. There were various manifestations of systemic toxicity, including damage to the liver and kidneys; a likely allergic syndrome as indicated by some cytological signs; transient stimulation of erythropoiesis; and penetration of nickel into the brain from the nasal mucous membrane along the olfactory pathway. Against a picture of mild to moderate chronic toxicity of nickel, its in vivo genotoxic effect assessed by the degree of DNA fragmentation in nucleated blood cells (the RAPD test) was pronounced, tending to increasing with the length of the exposure period. When rats were given orally, in parallel with the toxic exposure, a set of innocuous substances with differing mechanisms of expected bioprotective action, the genotoxic effect of NiO-NPs was found to be substantially attenuated. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.

Piezoelectric materials based on lead zirconate titanate are widely used in sensors and actuators. However, their application is limited because of high processing temperature, brittleness, lack of conformal deposition and, more importantly, intrinsic incompatibility with biological environments. Recent studies on bioorganic piezoelectrics have demonstrated their potential in these applications, essentially due to using the same building blocks as those used by nature. In this work, we used piezoresponse force microscopy (PFM) to study the domain structures and polarization reversal in the smallest amino acid glycine, which recently attracted a lot of attention due to its strong shear piezoelectric activity. In this uniaxial ferroelectric, a diverse domain structure that includes both 180° and charged domain walls was observed, as well as domain wall kinks related to peculiar growth and crystallographic structure of this material. Local polarization switching was studied by applying a bias voltage to the PFM tip, and the possibility to control the resulting domain structure was demonstrated. This study has shown that the as-grown domain structure and changes in the electric field in glycine are qualitatively similar to those found in the uniaxial inorganic ferroelectrics. © 2019 by the authors.

Nanoparticles (NPs) of Fe3O4 were produced by a chemical technique and NPs of Ag, Au, CuO, NiO, Mn3O4, PbO, ZnO, TiO2, SiO2, and Al2O3 - by laser ablation in water. In some experiments we compared particles of a given chemical composition having different diameters, while in others - equidimensional NPs of different metals or metal oxides (Me-NPs). We used two experimental models: a single intra-tracheal instillation of Me-NPs 24 h before the bronchoalveolar lavage procedure (collecting) and the repeated intra-peritoneal injections during 6-7 weeks in non-lethal doses. Besides, we carried out long-term inhalation experiments with NPs of Fe2O3, SiO2, and NiO. We have demonstrated that NPs are much more noxious than their fine micrometric or even submicron counterparts and are usually the more toxic the smaller their dimensions within the nanoscale range. We have found also that toxicity of Me-NPs strongly depends on their chemical nature, solubility, and specific mechanisms of characteristic action of a given metal in any chemical form. Solubility of Me-NPs in biological milieus plays an important role in their toxicokinetics, which can prevail over that of the physiological mechanisms controlling their distribution, retention, and elimination. On the other hand, thanks to the high activity of these mechanisms, the organism is not defenceless against the impact of Me-NPs. The toxicity and even genotoxicity of Me-NPs can be significantly decreased by adequately composed combinations of some bioactive agents in innocuous doses. © 2018 Institute of Physics Publishing. All rights reserved.

We present experimental study of domain kinetics in 36? Y-cut congruent lithium niobate during polarization reversal by increasing external electric field using liquid electrodes. The motion of the domain walls has been imaged on the Zs+ and Zs-polar surfaces of the crystal simultaneously. The linear dependence of the threshold field on the field rate has been revealed. The threshold field in low field rate limit has been estimated as 32.8 ? 0.3 kV/mm, which is lower than predicted value. The switching process for polarization reversal in the constant field has dramatically accelerated with increase of external electrical field above threshold. The new approach, which accelerates significantly the in situ study of 3D domain kinetics in CLN crystals, has been demonstrated. © 2018 Institute of Physics Publishing. All rights reserved.

We have studied the influence of initial domain structure on piezoelectric and dielectric properties of Sr 0.61 Ba 0.39 Nb 2 O 6 single crystals slightly doped with Ce and Ni. Initial domain structure was created by zero-field cooling, in-field cooling, and partial switching. The difference in the frequency dependences of macroscopic piezoelectric response and temperature dependences of dielectric permittivity for various initial domain structures was revealed. © 2018 Institute of Physics Publishing. All rights reserved.

We demonstrate the abilities of various SEM techniques for domain imaging in PMN-PT crystals with different compositions. It is shown that the imaging of the chemically etched relief is limited by its destructivity and potential contrast - by low resolution and contrast instability. The optimal parameters of the imaging by backscattered electron channelling allow obtaining the high-resolution domain imaging in PMN-PT crystals. The domain structure change as a result of the phase transition are imaged. The correlation between the images of the surface domain structure obtained by scanning electron microscopy and piezoresponse force microscopy is demonstrated. © 2018 Institute of Physics Publishing. All rights reserved.

The switching current shape during polarization reversal at room temperature by rectangular field pulses was studied. The activation-type external field dependence of switching time was revealed. The domain structure was imaged after partial polarization reversal by piezoresponse force microscopy with high-spatial resolution and the main geometrical parameters were extracted. The switching currents for complete polarization reversal in field range from 15 to 20 kV/mm were fitted by modified Kolmogorov-Avrami formula taking into account the geometrical parameters of the domain structure. The obtained excellent fitting of the switching current confirmed the proposed model of the switching process. © 2018 Institute of Physics Publishing. All rights reserved.

We studied microstructure, surface morphology, and domain structure of (Ba 0.75 ,Sr 0.25 )TiO 3 based glass-ceramics with different amount of Mn additive (from 0 to 0.5%) prepared from melted and quenched mixed powders using several microscopic methods. The as-quenched sample was annealed and subjected to a controlled crystallization in air for 2h at temperatures 850 and 950?C. It was shown that the addition of the Mn up to 0.5% had no impact on morphology and domain structure. The dendrite structure was revealed in the samples crystallized at 850?C. The geometry of the clusters was analysed in terms of fractal approach. The faceted grains with size about 150 nm were found in ceramics annealed at 950?C. Individual grains demonstrated non-uniform piezoresponse, which could be attributed to existence of domain structure. © 2018 Institute of Physics Publishing. All rights reserved.

We have studied the formation of isolated domains induced by ion beam irradiation in the stoichiometric lithium niobate (SLN) single crystals covered by surface dielectric layer. The unusual domain shape was revealed at the irradiated polar surface at the doses above 20 pC. The nested domain shape with hexagonal outer part and circle inner one has been distinguished. The domains visualization in the bulk showed the hexagonal domain shape in the depth. The obtained effect was attributed to backswitching under the action of electric field produced by space charge dipped to LN plate at the doses above 20 pC due to essential ion beam sputtering effect.

Morphological criteria of diagnosis of dust lesions of lungs in tumors on resection material are considered in the article. It is shown that the complex application of various research methods allows the identification of dust particles in the lung and lymph node tissues, and contributes to the improvement of the diagnosis of dust lesions of the respiratory system. Morphological characteristics of bauxite pneumoconiosis in primary lung cancer on resection material are presented.

The cubic (c) and monoclinic (m) polymorphs of Gd 2 O 3 were studied using the combined analysis of several materials science techniques – X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) spectroscopy. Density functional theory (DFT) based calculations for the samples under study were performed as well. The cubic phase of gadolinium oxide (c-Gd 2 O 3 ) synthesized using a precipitation method exhibits spheroidal-like nanoclusters with well-defined edges assembled from primary nanoparticles with an average size of 50 nm, whereas the monoclinic phase of gadolinium oxide (m-Gd 2 O 3 ) deposited using explosive pyrolysis has a denser structure compared with natural gadolinia. This phase also has a structure composed of three-dimensional complex agglomerates without clear-edged boundaries that are ∼21 nm in size plus a cubic phase admixture of only 2 at.% composed of primary edge-boundary nanoparticles ∼15 nm in size. These atomic features appear in the electronic structure as different defects ([Gd…O–OH] and [Gd…O–O]) and have dissimilar contributions to the charge-transfer processes among the appropriate electronic states with ambiguous contributions in the Gd 5р – O 2s core-like levels in the valence band structures. The origin of [Gd…O–OH] defects found by XPS was well-supported by PL analysis. The electronic and atomic structures of the synthesized gadolinias calculated using DFT were compared and discussed on the basis of the well-known joint OKT–van der Laan model, and good agreement was established. © 2017

Local electromechanical (EM) measurements were performed in Pr doped BiFeO3 (BPFO) ceramics via piezoresponse force microscopy (PFM). The results revealed that local EM response was different from the macroscopic one due to the large contribution of the leakage current. The locally measured response was used to evaluate effective piezoelectric coefficient d33 of the material. The multi-frequency PFM mode with additional compensation of the cantilever-surface Coulomb interaction under application of the external DC bias provided the most accurate values of the effective d33 coefficient and allowed studying its surface distribution and residual depolarization field distribution across the surface of BPFO ceramics. © 2018 Taylor & Francis Group, LLC.

Relaxor ferroelectrics exhibit a range of interesting material behavior, including high electromechanical response, polarization rotations, as well as temperature and electric field-driven phase transitions. The origin of this unusual functional behavior remains elusive due to limited knowledge on polarization dynamics at the nanoscale. Piezoresponse force microscopy and associated switching spectroscopy provide access to local electromechanical properties on the micro- and nanoscale, which can help to address some of these gaps in our knowledge. However, these techniques are inherently prone to artefacts caused by signal contributions emanating from electrostatic interactions between tip and sample. Understanding functional behavior of complex, disordered systems like relaxor materials with unknown electromechanical properties therefore requires a technique that allows distinguishing between electromechanical and electrostatic response. Here, contact Kelvin probe force microscopy (cKPFM) is used to gain insight into the evolution of local electromechanical and capacitive properties of a representative relaxor material lead lanthanum zirconate across the phase transition from a ferroelectric to relaxor state. The obtained multidimensional data set was processed using an unsupervised machine learning algorithm to detect variations in functional response across the probed area and temperature range. Further analysis showed the formation of two separate cKPFM response bands below 50 °C, providing evidence for polarization switching. At higher temperatures only one band is observed, indicating an electrostatic origin of the measured response. In addition, the junction potential difference, which was extracted from the cKPFM data, becomes independent of the temperature in the relaxor state. The combination of this multidimensional voltage spectroscopy technique and machine learning allows to identify the origin of the measured functional response and to decouple ferroele

La-modified lead zirconate titanate (PLZT) thin films were prepared to study their physical properties at macro- and nanoscale. Piezoresponse force microscopy (PFM) studies suggest a local imprint behavior at room temperature. Confirmed by P-E hysteresis loops recorded at 180-300 K, the imprint effect at room temperature tends to disappear at lower temperatures. In addition, the remanent polarization gradually increases and then decreases after reaching a maximum at around 243 K. This behavior suggests the occurrence of a reentrant dipole glass or an activated electric field effect in the studied PLZT films. © 2017 Taylor & Francis Group, LLC.

The following scenarios of Re-embedding into SiO2-host by pulsed Re-implantation were derived and discussed after XPS-and-DFT electronic structure qualification: (i) low Re-impurity concentration mode → the formation of combined substitutional and interstitial impurities with Re2O7-like atomic and electronic structures in the vicinity of oxygen vacancies; (ii) high Re-impurity concentration mode → the fabrication of interstitial Re-metal clusters with the accompanied formation of ReO2-like atomic structures and (iii) an intermediate transient mode with Re-impurity concentration increase, when the precursors of interstitial defect clusters are appeared and growing in the host-matrix structure occur. An amplification regime of Re-metal contribution majority to the final Valence Band structure was found as one of the sequences of intermediate transient mode. It was shown that most of the qualified and discussed modes were accompanied by the MRO (middle range ordering) distortions in the initial oxygen subnetwork of the a-SiO2 host-matrix because of the appeared mixed defect configurations. © 2017 Elsevier B.V.

Electrochemical strain microscopy (ESM) is a scanning probe microscopy (SPM) method in which the local electrodiffusion is probed via application of AC voltage to the SPM tip and registration of resulting electrochemical strain. Here, we implemented ESM to measure local strain in bulk LiMn2O4 cathodes of a commercial Li-battery in different states of charge to investigate distribution of Li-ion mobility and concentration. Ramped AC ESM imaging and voltage spectroscopy were used to find the most reliable regime of measurements allowing separating and diminishing different contributions to ESM. This is not a trivial task due to complex geometry of the sample and various obstacles resulting in less predictable contributions of different origins into ESM response: Electrostatic tip-surface interactions, charge injection, electrostriction, and flexoelectricity. Understanding and control of these contributions is an important step towards quantitative interpretation of ESM data. © 2016 AIP Publishing LLC.

Polycrystalline lanthanum lead zirconate titanate (PLZT) thin films were deposited on Pt/TiO2/SiO2/Si substrates to study the effects of the thickness and grain size on their structural and piezoresponse properties at nanoscale. Thinner PLZT films show a slight (100)-orientation tendency that tends to random orientation for the thicker film, while microstrain and crystallite size increases almost linearly with increasing thickness. Piezoresponse force microscopy and autocorrelation function technique were used to demonstrate the existence of local self-polarization effect and to study the thickness dependence of correlation length. The obtained results ruled out the bulk mechanisms and suggest that Schottky barriers near the film-substrate are likely responsible for a build-in electric field in the films. Larger correlation length evidence that this build-in field increases the number of coexisting polarization directions in larger grains leading to an alignment of macrodomains in thinner films. © 2016 Author(s).

Potential ferroelectricity in charge-transfer organic materials is often masked by the intrinsic conductivity. Here, we report the compelling evidence of ferroelectricity in organic π-conjugated meta-nitroaniline (m-NA) crystals as shown by the local electromechanical measurements using the piezoresponse force microscopy (PFM) technique. m-NA is a charge-transfer molecular material with the exceptional optical non-linearity and perceptible conductivity along the crystallographic polar axis. While standard Sawyer-Tower measurements revealed an apparently lossy-dielectric hysteresis, The PFM switching spectroscopy indicated clear ferroelectric behaviour in this technologically important multifunctional material. Further study of the pyroelectric properties in m-NA crystals confirmed their high spontaneous polarization of 18 μC/cm2 at room temperature, comparable to the best known organic ferroelectrics. © 2016 Author(s).

Randomly oriented Sr0.75Ba0.25Nb2O6 thin films have been deposited on Pt(111)/Ti/SiO2/Si substrates using a polymeric chemical method to study their physical properties. Refinements of the structure confirm the stoichiometry of the studied films. The relaxor behavior is evidenced by the dielectric measurements and Vögel-Fulcher analysis of the dielectric curves. Lowering the transition temperature (Tm) by about 100 K and asymmetries in the local hysteresis loops well above Tm are discussed in terms of the existence of complex defects in thin films. © 2016 Taylor & Francis Group, LLC.

Formation of domain structure by electron beam irradiation in congruent lithium niobate covered by surface dielectric layer with planar and channel waveguides produced by Soft Proton Exchange (SPE) process has been studied. Formation of domains with arbitrary shapes as a result of discrete switching has been revealed. The fact was attributed to ineffective screening of depolarization field in the crystals with a surface layer modified by SPE process. The dependences of the domain sizes on the dose and the distance between irradiated areas have been revealed. Finally, we have demonstrated that electron beam irradiation of lithium niobate crystals with surface resist layer can produce high quality periodical domain patterns after channel waveguide fabrication. Second harmonic generation with normalized nonlinear conversion efficiency up to 48%/(W cm2) has been achieved in such waveguides. © 2016 Author(s).

Domain shape evolution and domain wall motion have been studied in KTiOPO4 (KTP) ferroelectric single crystals using complementary experimental methods. The in situ visualization of domain kinetics has allowed revealing: (1) qualitative change of the domain shape, (2) dependence of the domain wall velocity on its orientation, (3) jump-like domain wall motion caused by domain merging, (4) effect of domain shape stability. The model of domain wall motion driven by generation of elementary steps (kink-pair nucleation) and subsequent kink motion is presented. The decrease in the relative velocity of the approaching parallel domain walls is attributed to electrostatic interaction. The effect of polarization reversal induced by chemical etching is observed. The obtained results are important for the development of domain engineering in the crystals of KTP family. © 2016 Author(s).