Iliya A. Verbenko

Ferro-piezoceramic materials (FPCM) with different degrees of ferrohardness were fabricated by double solid-phase synthesis followed by the sintering technique using hot pressing method. The X-ray studies carried out in a wide temperature range showed that with increasing temperature, each of the studied FPCM undergoes a series of phase transformations, accompanied by a change in the symmetry of the unit cell. In this case, near the phase transition to the nonpolar cubic phase, in each of the FPCM, the formation of a fuzzy symmetry region is observed, which is characterized by weak distortions and temperature–time instability of the crystal structure. The study of the piezoelectric modulus d₃₃ in the quasi-static regime as a function of temperature made it possible to reveal the different nature of its behavior in materials of various degrees of ferrohardness. It was shown that the conservation of the state in ferrosoft materials above the Curie temperature is associated with the relaxation nature of the change in their properties, the existence of a region of fuzzy symmetry (noncubic phase) in them above the Curie temperature, and increased inertia of the system. The expediency of taking into account the presented results in the development of electromechanical converters based on FPCM of various degrees of ferrohardness, operated under temperature effects, including cyclic ones, was shown.

The crystal structure and surface morphology of ceramics as well dielectric and thermal properties of Bi_1−xEr_xFeO₃ (where x = 0.05 − 0.20, Δх = 0.05) magnetoelectric solid solutions (SS) were investigated. The regularities of changes in phase composition, microstructure, electrical and dielectric properties of objects at room temperature are established.

The investigation results of the processes of phase formation in barium niobate, strontium, and their solid solutions in the conditions of the variability of the thermodynamic background are presented. The formation of a grain landscape and dielectric properties (including relaxation phenomena) in the solid solutions of strontium niobate and their solid solutions and the establishment of regularities in the formation of radio-absorbing properties in them are studied.

We investigated and presented our results for the dependence of the characteristics of the crystalline and grain structures of the PCR-13 material (based on the lead zirconate titanate (PZT) system), which was sintered in various ways, on the regulations for its preparation. The data from the microfluorescence analysis of the surface of ceramic materials were provided, which allowed us to state that micro X-ray fluorescence spectrometry (MICRO–XRF), supplemented by mathematical statistics, allows us to trace even small changes in the chemical composition of ceramic samples, reliably characterize the degree of surface homogeneity and provide strict mathematical conclusions related to the reproducibility of the properties of manufactured piezoelectric ceramic materials. Based on the obtained data, the optimal conditions for ceramics have been selected, which ensure homogeneity, high-density structure and reproducibility of the characteristics. This allows us to reliably use the material in frequency-selective equipment.

Conditions for fabricating (Ba_0.5Sr_0.5)Nb₂O₆ ceramics are optimized. It is shown that materials synthesized at T = 1250°C and sintered at T = 1375–21400°C exhibit the best ceramic characteristics. The (Ba_0.5Sr_0.5)Nb₂O₆ solid solution is found to be a ferroelectric with a diffuse phase transition. The possibility of fabricating Ba_0.5Sr_0.5Nb₂O₆ thin films from ceramic targets prepared in the resulting optimum regimes is shown.

Features of the thermal and frequency dependence of dielectric permeability in solid solutions based on the (Na, Li)NbO₃ system are investigated. It is established that the high-temperature anomalies of dielectric properties are associated with the partial reduction of niobium.

Ceramics of a modified Ba multicomponent system of PbNb2/3Zn1/3O3-PbNb2/3Mg1/3O3-PbNb2/3Ni1/3O3-PbTiO3were developed. A comprehensive study was peformed of the reversible dielectric nonlinearity and...

High-quality ceramics were synthesized on the basis of Bi1 − x A xFeO3 ( A = La, Nd; 0.00 ≤ x≤ 0.20) solid solutions. Their crystal and grain structure, Mössbauer spectra, and other dielectric and...