Olga Yu Sinelshchikova

Using the method of coprecipitation followed by hydrothermal treatment, nanoparticles of potassium polytitanates with titanium atoms shielded with nickel in amounts from 2,5 % to 10% were obtained. According to scanning electron microscopy, quasi-one-dimensional nanoparticles are formed during synthesis. The paper presents the results of a study of the sorption properties of potassium polytitanate nanoparticles doped with nickel, using the example of a reaction with the model dye methylene blue.

This article presents the results of a study of the concentration limits of the existence of the hollandite phase in the Cs₂O–Al₂O₃–TiO₂ system. A number of samples with different ratios of cesium, aluminum, and titanium are obtained by combustion of citrate–nitrate compositions. The phase composition and microstructure of the obtained materials are studied using X-ray phase analysis and scanning electron microscopy. When studying the electrical properties, it is found that the Cs_1.16Al_1.84Ti_6.33O₁₆ (σ = 5.45 × 10^–5 S/cm at T = 750°C) has the highest specific electrical conductivity.

Flexible crystal(水晶) structures, which exhibit(展览) single-crystal(水晶)-to-single-crystal(水晶) (SCSC) transformations(转型), are attracting attention(注意) in many applied aspects: magnetic(磁) switches, catalysis, ferroelectrics and sorption. Acid treatment(治疗) for titanosilicate material(材料) AM-4 and natural(自然) compounds with the same structures led to SCSC transformation(转型) by loss(损失) Na⁺, Li⁺ and Zn²⁺ cations with large structural(结构) changes (20% of the unit(单位)-cell(细胞) volume(体积)). The conservation(保育) of crystallinity through complex(复杂) transformation(转型) is possible due(由于) to the formation(形成) of a strong hydrogen bonding(债券) system(系统). The mechanism(机制) of transformation(转型) has been characterized using single-crystal(水晶) X-ray(射线) diffraction analysis(分析), powder(粉) diffraction, Rietvield refinement, Raman spectroscopy and electron microscopy. The low migration(迁移) energy(能源) of cations in the considered materials(材料) is confirmed using bond(债券)-valence and density(密度) functional(功能) theory(理论) calculations, and the ion conductivity of the AM-4 family’s materials(材料) has been experimentally verified.

The authors were not aware of errors made in the proofreading phase, and, hence, wish to make the following corrections to this paper

A metamaterial based on periodic ferroelectric inhomogeneities in a magnetic ferrite matrix including a quantity of ferroelectric composite in a matrix, demonstrating relative low microwave losses and effective dielectric permittivity, was produced. Glass-ceramic composites, consisting of low-melting glass and barium-strontium titanate, were successfully synthesized and incorporated into the periodic holes of the ferrite matrix to build the meta-structure. Investigation of the structure showed dielectric permittivity, which increased with the volume of ferroelectric inclusions. The range of magnetically controlled interactions of the meta-structures with an electro-magnetic field was increased for the matrix with periodic holes filled by the ferroelectric composite in comparison with the basic ferrite matrix. The ferrite substrate completely determined the microwave losses of the sample and the ferroelectric inclusions increased the Q-factor of the meta-structure.

Ceramics based on hollandites are known to mainly produced by the conventional solid-phase method. However, the use of various sol–gel methods in some cases makes it possible to change the temperature and time its synthesis, morphological characteristics, porosity, and electrophysical properties. In this work, ceramic materials based on a number of cesium titanate hollandite phases were synthesized by combustion of citrate–nitrate mixtures. The structure of the obtained materials was studied by X-ray powder diffraction analysis and scanning electron microscopy. Investigation of the electrophysical properties showed that, in a hydrogen flow, the electrical conductivity of hollandites with aluminum and nickel increases significantly (by 2.5–3 orders of magnitude) throughout the studied temperature range. Thus, ceramics based on these hollandites can be considered promising for creating hydrogen sensors and fuel cells.

Introduction. Materials exhibiting high dielectric permittivity are relevant for use in modern ultrahigh-frequency electronics. Among them, ferroelectrics with high dielectric nonlinearity present particular interest. The electrical strength of ferroelectric materials can be increased using modern composite structures based on mixing ferroelectries and linear dielectrics - materials exhibiting simultaneously low dielectric permittivity and high electrical strength. This approach provides for the opportunity of creating new multicomponent materials with previously unattainable properties and adjusting their component composition, inclusion size and electrical properties across a wide range. In this work, on the basis of porous potassium-iron-silicate glass (KFS) obtained by ion exchange, glass-ceramic materials containing barium titanate were synthesized for use at ultrahigh frequencies.Aim. Production of glass composites by low-temperature sintering of pre-synthesized BaTiO₃ (BTO) and potassium-iron-silicate glass, as well as characterization of their structural and electrical properties at ultrahigh frequencies (microwave).Materials and methods. The crystal structure and phase composition of the obtained films were studied by X-ray diffraction using a DRON-6 diffractometer by the emission spectral line CuK_α1 (λ = 1.5406 Å). The dielectric permittivity (ε) of microwave samples was evaluated by the Nicholson-Ross method at room temperature using an Agilent E4980A LCR-meter.Results. According to X-ray diffraction analysis, the synthesized samples are a mixture of KFS glass, ferroelectric BaTiO₃ and dielectric barium polytitanates; the ratio of the latter determines the electrical properties of the composites. Depending on the content of barium titanate, the studied samples demonstrate a dielectric constant from 50 to 270 at a dielectric loss level of 0.1...0.02. The samples subjected to annealing in an oxygen medium showed an increase in dielectric permittivity by 10.25 % and an increase in controllability with a decrease in dielectric losses by an average of two times.Conclusion. The composite composition of 70 wt % BTO /30 wt % KFS was found to be the most promising in terms of structural and electrical properties. This composite showed an increase in dielectric permittivity by 25 % and a significant increase in nonlinearity, at the same time as reducing losses by more than two times as a result of annealing in an oxygen medium.