In this paper, a study of a graphite intercalation compound by potassium was carried out using Raman spectroscopy. The purpose of the study was to determine the intercalation stage and study the influence of intercalated atoms on the vibrational properties of highly oriented pyrolytic graphite lattice. The intercalation of highly oriented pyrolytic graphite by potassium was performed using a two-zone method. Raman spectra were obtained for both pure and intercalated highly oriented pyrolytic graphite. The experiments carried out to identify the synthesized structures showed the formation of sixth stage graphite intercalation compound. Knowledge of the stage of the intercalated graphite compounds is important for its use as a superconducting material, as well as in supercapacitors. In addition, the intercalation stage is a key factor in obtaining graphene by chemical exfoliation of graphite intercalation compound, since the number of graphene layers will directly depend on the intercalation stage. In the obtained Raman spectra, the effect of G-peak splitting is observed, indicating a change in the vibrational properties of the graphite lattice during its intercalation due to the charge transfer from the intercalate to the carbon layers. The value of the transferred charge is determined using first-principles calculations.

Introduction of dopants is a classic method for modifying the properties of materials, in particular, complex oxides of the perovskite family with the general formula ABO3. Ions located in positions A and/or B are substituted. In this case, their valence can coincide with the valence of the basic ion (isovalent substitution) or differ (heterovalent substitution). Sodium niobate (NaNbO3) is a convenient basis for producing ferroelectric solid solutions. Doping changes the properties of sodium niobate in a wide range, allowing the production of functional materials for various applications. In this paper, the effect of Bi3+ doping upon substitution of niobium ion Nb5+ on the structure and electrophysical properties of sodium niobate is studied. It has been shown that such compositions are characterized by a significant increase in electrical conductivity with increasing the doping concentration, a decrease in the Curie temperature, and a change in the grain structure. The dopant concentration is more than 10 mol. % leads to the formation of some secondary phases.

Results are presented from optical profilometry and scanning probe microscopy studies of the structures and surface parameters of germanium single crystals exposed to an alternating magnetic field. A change in the relief and surface roughnesses of the crystals after magnetic field processing and a drop in their optical transmittance in the range of 1.8–23 μm are established.

An investigation is performed of the temperature dependence of the permittivity and electrical conductivity of sodium niobate ceramics doped with iron or bismuth in a wide range of frequencies of the external field. Phase transitions and their character are revealed for the considered solid solutions and conduction mechanisms.

The work presents the results of green synthesis (biosynthesis) of silver nanoparticles using aqueous extracts of maple and oak leaves. The efficiency of the synthesis, size and shape of the formed nanoparticles were studied using UV-visible spectroscopy, dynamic light scattering, atomic force microscopy and scanning electron microscopy techniques. It was found that the formation of silver nanoparticles is accompanied by the appearance of a plasmon resonance band in the electronic spectra of aqueous extracts, the maximum of which depends on the concentration of silver nitrate and is in the range of similar to 420-429 nm in the spectra of maple leaves, and in the spectra of oak extracts there is a shift towards longer wavelengths similar to 425-435 nm, which correspond to the formation of nanoparticles of larger size. According to the dynamic light scattering data, the size of nanoparticles in the maple extracts is of about 60-68 nm and in the oak samples of similar to 107 nm. The differences in the size and shape of nanoparticles obtained in the maple and oak phytoextracts detected by atomic force microscopy and scanning electron microscopy are explained by the different composition of bioactive substances in the plants involved in the reduction of silver ions and stabilization or modification of the surface of silver nanoparticles.

The paper considers the preparation of potassium sodium niobate ceramics doped with titanium in an amount of 5 mol. %. The structure and dielectric properties were investigated in the temperature range 30–650 °C. It is shown that acceptor doping leads to a decrease in the grain size. Violation of stoichiometry in the anionic sublattice contributes to a decrease in the relaxation time of thermal ionic polarization compared to the case of nonstoichiometry in the cationic sublattice.

The work is devoted to investigation of the influence of the technology for producing potassium sodium niobate ceramics with an acceptor impurity Ti4+ on its structure and dielectric properties. The aim of the work was to determine ways to obtain a single-phase composition of doped ceramics and the role of the TiO2 modifying impurity. It is shown that the substitution of niobium by titanium for preserves the cubic shape of potassium sodium niobate grains, increases dielectric losses and causes significant migration polarization. The latter leads to the fact that the maximum temperature dependence of the dielectric permittivity at low frequencies is not observed for the studied ceramics. The shift of the phase transition temperature caused by doping is not observed. In all samples, despite the heterogeneity of the elemental composition and grain structure, the phase transition temperature corresponds to the phase transition temperature of pure potassium sodium niobate ceramics.

The results of studies of the structure, as well as piezoelectric, and dielectric properties, of lead zirconate-titanate ceramics modified with various concentrations of lanthanum (PLZT) are presented. It is found that with an increase in the La content, the grain size and the average size of the domains increase. The PLZT 12/40/60 samples contain both labyrinthine-like and periodic domains and different lateral sizes ranging from several hundred nanometers to 3 μm in diameter. It is found that with an increase in the size of domains in samples with a high content of lanthanum the signal of the piezoelectric response is enhanced. The fact of the existence of areas on the surface of PLZT x /40/60 ceramics, having an internal bias field, as indicated by the asymmetry along the voltage axis of the residual piezoelectric hysteresis loops, is established. In the PLZT 5/40/60 and PLZT 12/40/60 samples, a significant dispersion of the dielectric constant ε( f ) and the maximum tangent of the dielectric loss angle in the frequency range from 10 5 to 10 6 Hz are observed. This is due to the presence of ionic relaxation polarization. It is found that the value of the dielectric constant increases markedly with an increase in La, which confirms the appearance of a rigid unipolar state in the grains of the PLZT 12/40/60 ceramics. In the samples under study, at low frequencies of the measuring field, an increase in the dielectric loss tangent is observed, which is related to the contribution of the conductivity to tan δ. The dependences of the dielectric loss factor ε'' on the dielectric constant ε' are plotted. They have the form of Cole–Cole diagrams, which indicates the presence of a spectrum of relaxation times, and it is found that the spectral width in the PLZT 5/40/60 samples is approximately half that in the PLZT 12/40/60 samples.

В работе представлены результаты исследований микро- и наноструктуры поверхности быстрозакаленных лент сплавов Гейслера (NiMnAl,NiMn AlSi, NiCoMn Al) методами сканирующей электронной и атомно-силовой микроскопии. Рассмотрено влияние химического состава на размер, геометрию границ и структуру зерен. Показано, что все исследуемые образцы обладают наноразмерным мартенситным рельефом, определены его параметры. Установлено, что поперечное сечение лент представлено кристаллическими зернами разной формы и размера, что обусловлено отличием скоростей охлаждения по краям и в центре ленты. Проведено элементное картирование поверхности поперечного сечения лент с помощью рентгеновского энергодисперсионного спектрометра, установлено равномерное распределение химических элементов в образцах. Показано, что легирование лент состава NiMnAl кобальтом вызывает изменение микроморфологии поверхности и оказывает значительное влияние на ход полевых зависимостей намагниченности и доменную структуру образцов. The paper describes the results of the scanning electronic and atomic force microscopy research of the surface structure of the NiMn Al, NiMn AlSi, NiCoMnAl rapidly quenched ribbons. The influence of the chemical composition on the size, boundary geometry and structure of the grains is considered. It is shown that all the test samples have a nano-sized martensitic relief, and its parameters are determined. It has been established that the cross section of the ribbon is represented by crystalline grains of different shapes which are due to differences in the cooling rates along the edges and in the center of the samples. Elemental mapping of the cross-sectional surface of the ribbons was carried out using an X-ray energy dispersive spectrometer, and a uniform distribution of chemical elements in the samples was established. It is shown that the cobalt doping of NiMn Al ribbon causes changes in the micromorphology of the surface and has a significant effect on the magnetic properties of rapidly quenched ribbons: field dependences of themagnetization and domain structure.

In the present work, we study mixed compounds based on Ca0.28Ba0.72Nb2O6 (CBN28) calcium–barium niobate, and Sr0.61Ba0.39Nb2O6 (SBN61) strontium–barium niobate single crystals. It is shown that electron radiation in an electron microscope (with an accelerating voltage of 15 kV) during the scanning process induces the enhanced DC conductivity of samples along with a drastic rise in the dielectric constant. Furthermore, the dielectric constant as a function of the temperature changes its course, leading to a strong increase in dielectric loss at frequencies below 10 kHz.

The article presents the results of research of the grains surfaces piezoelectric ceramics with ABO(3)composition using scanning electron microscopy and atomic force microscopy. The dependences of the shape and size of the grains on the cation in position A are detected. Growth steps are observed on the surface of the grains. Domain walls on such grains are perpendicular to the growth steps.

In our work, we obtained and studied the samples of porous piezoelectric ceramics based on lithium - sodium niobate (LNN) with a pore content of 10, 20, 30, and 40 volume percent. An analysis of the structure, temperature and frequency dependences of the permittivity of the samples was carried out. It was shown that in all samples there are two main relaxation processes: in the regions of high (1 - 7 MHz) and low (10 Hz - 1 MHz) frequencies. The frequency at which a change in the type of dispersion occurs depends on the pores concentration in the sample.

The dependence of the microstructure and domain structure of sodium niobate ceramics on the production conditions (synthesis temperature of the initial composition and sintering temperature of the samples) was studied by scanning electron microscopy (SEM) and piezoelectric force microscopy (PFM). It is found that the samples whose material was obtained without re-synthesis have a larger grain size. The deleting of re-synthesis makes it possible to obtain sodium niobate ceramics with ferroelectric properties at the 1100 degrees C sintering temperature, while for samples which are obtained by double synthesis, they appear only at sintering temperatures above 1200 degrees C.

Introduction of dopants is a classic method for modifying properties of perovskite complex oxides of the family of general formula ABO3 . Sodium niobate NaNbO3 is widely used as a basis for creating solid solutions. The introduction of substitutional cations is carried out at both position A and at position B. Of particular interest is the case when valence of the dopant is greater or less than valence of the initial cation at the site. In this case, a defected structure is formed, which may have unique properties. This work is devoted to study of the electrical properties of sodium niobate ceramics doped with Fe3+. The substitution was carried out according to positions of the nibium cations Nb5+. It is shown that such compositions are characterized by a significant increase in electrical conductivity, a decrease in the Curie temperature, and a diffuse of the phase transition.