Study of the fatigue endurance and mechanical strength of solid solutions of the PZT–PZN–PMN system, modified with Ba and Sr, corresponding to the formula (Pb1−α1−α2Srα1Baα1) [TixZry〈(Nb2/3Zn1/3) (Nb2/3Mg1/3)〉1−x−y]O3, with α1 = 0.02 ÷ 0.12; Δα1 = 0.02, α2 = 0.0036 ÷ 0.073; x= 0.385 ÷ 0.430, y= 0.402 ÷ 0.447 is presented. It is shown that the evolution of the polarization characteristics with an increase in the number of repolarization cycles, n, is characterized by two sections: slow fatigue and logarithmic evolution. It was found that an increase in the strontium content shifts the beginning of the logarithmic stage towards to the large n. It is shown that an increase in the average grain size decreases the mechanical strength. A conclusion is made about the expediency of using the obtained data in the development of devices operating in power modes.Study of the fatigue endurance and mechanical strength of solid solutions of the PZT–PZN–PMN system, modified with Ba and Sr, corresponding to the formula (Pb1−α1−α2Srα1Baα1) [TixZry〈(Nb2/3Zn1/3) (Nb2/3Mg1/3)〉1−x−y]O3, with α1 = 0.02 ÷ 0.12; Δα1 = 0.02, α2 = 0.0036 ÷ 0.073; x= 0.385 ÷ 0.430, y= 0.402 ÷ 0.447 is presented. It is shown that the evolution of the polarization characteristics with an increase in the number of repolarization cycles, n, is characterized by two sections: slow fatigue and logarithmic evolution. It was found that an increase in the strontium content shifts the beginning of the logarithmic stage towards to the large n. It is shown that an increase in the average grain size decreases the mechanical strength. A conclusion is made about the expediency of using the obtained data in the development of devices operating in power modes.

Piezoelectric properties and related figures of merit are studied in novel 1–3-type composites based on ferroelectric domain-engineered lead-free single crystal with the relatively large longitudinal piezoelectric coefficient d33. Relationships between the piezoelectric properties and the set of figures of merit are analyzed for the 1–3 and 1–3–0 composites that contain the same single-crystal and polymer components. For a composite characterized by 1–3–0 connectivity, an influence of a porous piezo-passive matrix on the figures of merit and their volume-fraction behavior is considered additionally. A large anisotropy of figures of merit is observed in the 1–3–0 composite with specific porous matrices. A diagram is put forward to show volume-fraction regions of the large anisotropy of figures of merit of the studied 1–3–0 composite. Due to large figures of merit and their considerable anisotropy, the studied lead-free composites can be applied in piezoelectric energy-harvesting systems, sensors, transducers, and so on.Piezoelectric properties and related figures of merit are studied in novel 1–3-type composites based on ferroelectric domain-engineered lead-free single crystal with the relatively large longitudinal piezoelectric coefficient d33. Relationships between the piezoelectric properties and the set of figures of merit are analyzed for the 1–3 and 1–3–0 composites that contain the same single-crystal and polymer components. For a composite characterized by 1–3–0 connectivity, an influence of a porous piezo-passive matrix on the figures of merit and their volume-fraction behavior is considered additionally. A large anisotropy of figures of merit is observed in the 1–3–0 composite with specific porous matrices. A diagram is put forward to show volume-fraction regions of the large anisotropy of figures of merit of the studied 1–3–0 composite. Due to large figures of merit and their considerable anisotropy, the studied lead-free composites can be applied in piezoelectric energy-harvesting systems, sensors, transducers, and so on.

Within the framework of the linearized theory of electroelastic wave propagation, a model of a piezoelectric structure with a prestressed functionally graded coating made of piezoceramics of a trigonal system with a symmetry class of 3m is considered. The ferroelectric LiNbO3 is used as the main material of the structure. The initial deformed state of the coating material is homogeneous, induced by the action of initial mechanical stresses and an external electrostatic field, the properties of the coating continuously change in thickness. By the example of the problem of the propagation of SH-waves from a remote source for structures with an inhomogeneous prestressed coating in the case of an electrically free and short-circuited surface, the influence of the nature and localization of the inhomogeneity of the coating on the features of SAW propagation is studied. The separate and combined effects of initial actions on changes in the physical properties of the structure, the transformation of the surface wave field, and the change in the SAW velocities in a wide frequency range is studied. The results obtained in this work are useful for understanding the dynamic processes in prestressed piezoelectric structures, in the optimization and design of new structures and devices on SAW with high performance characteristics.Within the framework of the linearized theory of electroelastic wave propagation, a model of a piezoelectric structure with a prestressed functionally graded coating made of piezoceramics of a trigonal system with a symmetry class of 3m is considered. The ferroelectric LiNbO3 is used as the main material of the structure. The initial deformed state of the coating material is homogeneous, induced by the action of initial mechanical stresses and an external electrostatic field, the properties of the coating continuously change in thickness. By the example of the problem of the propagation of SH-waves from a remote source for structures with an inhomogeneous prestressed coating in the case of an electrically free and short-circuited surface, the influence of the nature and localization of the inhomogeneity of the coating on the features of SAW propagation is studied. The separate and combined effects of initial actions on changes in the physical properties of the structure, the transformation of the surface wave field, and the change in the SAW velocities in a wide frequency range is studied. The results obtained in this work are useful for understanding the dynamic processes in prestressed piezoelectric structures, in the optimization and design of new structures and devices on SAW with high performance characteristics.

SnO2–ZnO thin films consisting of nanoscale crystallites were obtained on glass and silicon substrates by solid-phase low-temperature pyrolysis. The synthesized materials were studied by XRD and SEM methods, electrophysical and optical properties were evaluated, as well as the band gap was calculated. It was shown that regardless of the phase composition all films were optically transparent in the visible range (310–1000 nm). The nanocrystallites’ minimum size, the highest activation energy of the conductivity and the smallest band gap calculated for indirect transitions were shown for a thin film 50SnO2–50ZnO. It was assumed that the band gap decreasing might be attributed to the existence of surface electric fields with a strength higher than 4 × 105 V/cm.SnO2–ZnO thin films consisting of nanoscale crystallites were obtained on glass and silicon substrates by solid-phase low-temperature pyrolysis. The synthesized materials were studied by XRD and SEM methods, electrophysical and optical properties were evaluated, as well as the band gap was calculated. It was shown that regardless of the phase composition all films were optically transparent in the visible range (310–1000 nm). The nanocrystallites’ minimum size, the highest activation energy of the conductivity and the smallest band gap calculated for indirect transitions were shown for a thin film 50SnO2–50ZnO. It was assumed that the band gap decreasing might be attributed to the existence of surface electric fields with a strength higher than 4 × 105 V/cm.

This paper presents a numerical homogenization analysis of a porous piezoelectric composite with a partially metalized pore surface. The metal layers can be added to the pore surfaces to improve the mechanical and electromechanical properties of ordinary porous piezocomposites. Physically, constructing that composite with completely metalized pore surfaces is a challenging process, and imperfect metallization is more expected. Here, we investigate the effects of possible incomplete metallization of pore surfaces on the composite’s equivalent properties. We applied the effective moduli theory, which was developed for the piezoelectric medium based on the Hill–Mandel principle, and the finite element method to compute the effective moduli of the considered composites. Using specific algorithms and programs in the ANSYS APDL programming language, we constructed the representative unit cell element models and performed various computational experiments. Due to the presence of metal inclusion, we found that the dielectric and piezoelectric properties of the considered composites differ dramatically from the corresponding properties of the ordinary porous piezocomposites. The results of this work showed that piezocomposites with partially metallized pore surfaces can have a higher anisotropy, compared to the pure piezoceramic matrix, due to the defects in metal coatings.This paper presents a numerical homogenization analysis of a porous piezoelectric composite with a partially metalized pore surface. The metal layers can be added to the pore surfaces to improve the mechanical and electromechanical properties of ordinary porous piezocomposites. Physically, constructing that composite with completely metalized pore surfaces is a challenging process, and imperfect metallization is more expected. Here, we investigate the effects of possible incomplete metallization of pore surfaces on the composite’s equivalent properties. We applied the effective moduli theory, which was developed for the piezoelectric medium based on the Hill–Mandel principle, and the finite element method to compute the effective moduli of the considered composites. Using specific algorithms and programs in the ANSYS APDL programming language, we constructed the representative unit cell element models and performed various computational experiments. Due to the presence of metal inclusion, we found that the dielectric and piezoelectric properties of the considered composites differ dramatically from the corresponding properties of the ordinary porous piezocomposites. The results of this work showed that piezocomposites with partially metallized pore surfaces can have a higher anisotropy, compared to the pure piezoceramic matrix, due to the defects in metal coatings.

The aim of this study is to optimize the conditions for producing thin VO2 films for their use in SAW devices. We used the pulsed laser deposition (PLD) method to produce VO2 films. We used a metallic vanadium target. The dependence of the oxygen pressure during PLD on the resistive metal–insulator transition (MIT) on substrates of c-sapphire and LiNbO3 YX/128∘ was studied. The resulting films had sharp metal–insulator temperature transitions on c-Al2O3. The most high-quality films showed resistance change by four orders of magnitude. At the lower point of the hysteresis, the resistance of these samples was in the range of 50–100 Ω. The synthesized VO2 films had a sharp temperature transition and a relatively small width of thermal hysteresis. The SAW damping during its passage through a VO2/ZnO/LiNbO3 YX/128∘ film at the metal–insulator phase transition temperature was studied. Attenuation SAW decreases with increasing temperature from 52 dB/cm to 0 dB/cm.The aim of this study is to optimize the conditions for producing thin VO2 films for their use in SAW devices. We used the pulsed laser deposition (PLD) method to produce VO2 films. We used a metallic vanadium target. The dependence of the oxygen pressure during PLD on the resistive metal–insulator transition (MIT) on substrates of c-sapphire and LiNbO3 YX/128∘ was studied. The resulting films had sharp metal–insulator temperature transitions on c-Al2O3. The most high-quality films showed resistance change by four orders of magnitude. At the lower point of the hysteresis, the resistance of these samples was in the range of 50–100 Ω. The synthesized VO2 films had a sharp temperature transition and a relatively small width of thermal hysteresis. The SAW damping during its passage through a VO2/ZnO/LiNbO3 YX/128∘ film at the metal–insulator phase transition temperature was studied. Attenuation SAW decreases with increasing temperature from 52 dB/cm to 0 dB/cm.

The research findings of the phase composition, nanostructure and optical properties of strontium–barium niobate thin films are discussed. SrxBa1−xNb2O6 nanosized films (x = 0.5 and 0.61) were characterized by XRD, SEM and AFM studies. Reflective multi-angle ellipsometry and spectrophotometry were used to determine the optical parameters (refractive index, its dispersion, and thickness of the damaged surface layer) of thin films. It was shown that SBN-50 and SBN-61 thin films were grown c-oriented on Al2O3 (0001) and heteroepitaxial on MgO (001) substrates. The increase of refractive index, approaching its maximum value in the bulk material for a given composition as the film thickness increases, is observed.The research findings of the phase composition, nanostructure and optical properties of strontium–barium niobate thin films are discussed. SrxBa1−xNb2O6 nanosized films (x = 0.5 and 0.61) were characterized by XRD, SEM and AFM studies. Reflective multi-angle ellipsometry and spectrophotometry were used to determine the optical parameters (refractive index, its dispersion, and thickness of the damaged surface layer) of thin films. It was shown that SBN-50 and SBN-61 thin films were grown c-oriented on Al2O3 (0001) and heteroepitaxial on MgO (001) substrates. The increase of refractive index, approaching its maximum value in the bulk material for a given composition as the film thickness increases, is observed.

This work presents the results of study of the electrophysical properties of composite polymer ceramics (1?x)[KNN-LTSN]–xPVDF at x = 25 vol.% and x= 50 vol.% in the temperature range of T = 20–160°C and frequency range of f = 2 × 101–2 × 106 Hz. The concentration dependence of piezomodules of the studied materials has been analyzed as a function of temperature. X-ray measurements have also been carried out. A model of description of revealed dielectric parameters dispersion in the material is presented. The nonclassical modified Havriliak–Negami model written for complex electrical conductivity has been used to describe the temperature–frequency properties. It is shown that the dielectric spectra of the studied composites include three relaxation processes in the temperature ranges of 40–80°C, 80–120°C and 120–150 °C, which were confirmed by the dynamics of changes in the dependences of γ′(f), tgδ(f), M′(f), M′′(f) and M′′(M′). All three processes are almost exactly described by this model and well correlated with the studies by other researchers of the composites based on PVDF. The results of this work show that the use of such experimental model is suitable for describing the complex dielectric spectra of any nonlinear dielectrics including composite materials.This work presents the results of study of the electrophysical properties of composite polymer ceramics (1?x)[KNN-LTSN]–xPVDF at x = 25 vol.% and x= 50 vol.% in the temperature range of T = 20–160°C and frequency range of f = 2 × 101–2 × 106 Hz. The concentration dependence of piezomodules of the studied materials has been analyzed as a function of temperature. X-ray measurements have also been carried out. A model of description of revealed dielectric parameters dispersion in the material is presented. The nonclassical modified Havriliak–Negami model written for complex electrical conductivity has been used to describe the temperature–frequency properties. It is shown that the dielectric spectra of the studied composites include three relaxation processes in the temperature ranges of 40–80°C, 80–120°C and 120–150 °C, which were confirmed by the dynamics of changes in the dependences of γ′(f), tgδ(f), M′(f), M′′(f) and M′′(M′). All three processes are almost exactly described by this model and well correlated with the studies by other researchers of the composites based on PVDF. The results of this work show that the use of such experimental model is suitable for describing the complex dielectric spectra of any nonlinear dielectrics including composite materials.

The Aurivillius phases [Bi2O2][An−1BnO3n+1] are well-known ferroelectrics with high Curie temperatures TC. High-temperature piezoceramics Bi3−xGdxTiTaO9 (BGdTTa, x= 0.0, 0.1, 0.2, 0.3) were prepared by a solid-state reaction method. The structural and electrophysical characteristics of BGdTTa ceramics have been studied. According to the data of powder X-ray diffraction, all the compounds are single-phase with the structures of two-layer Aurivillius phases (m = 2) with the orthorhombic crystal lattice (space group A21am). The temperature dependence of the relative permittivity 𝜀/𝜀0 (T) of the compounds was measured and showed that the Curie temperature TC of perovskite-like oxides Bi3−xGdxTiTaO9 increases linearly with an increase in the substitution parameter x to TC = 925∘C. The activation energies of charge carriers have been found in different temperature ranges.The Aurivillius phases [Bi2O2][An−1BnO3n+1] are well-known ferroelectrics with high Curie temperatures TC. High-temperature piezoceramics Bi3−xGdxTiTaO9 (BGdTTa, x= 0.0, 0.1, 0.2, 0.3) were prepared by a solid-state reaction method. The structural and electrophysical characteristics of BGdTTa ceramics have been studied. According to the data of powder X-ray diffraction, all the compounds are single-phase with the structures of two-layer Aurivillius phases (m = 2) with the orthorhombic crystal lattice (space group A21am). The temperature dependence of the relative permittivity 𝜀/𝜀0 (T) of the compounds was measured and showed that the Curie temperature TC of perovskite-like oxides Bi3−xGdxTiTaO9 increases linearly with an increase in the substitution parameter x to TC = 925∘C. The activation energies of charge carriers have been found in different temperature ranges.

The electrophysical and structural characteristics of bismuth titanate oxides of a number of phases of solid solutions of the Aurivillius phases Bi7−2xNd2xTi4NbO21 (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) having a layered structure of the perovskite type have been investigated. According to the XRD data, all studied compounds are single-phase and have a mixed-layer structure of Aurivillius phases (m = 2.5) with a rhombic crystal lattice (space group I2cm, Z = 2). A relationship has been established between changes in the chemical composition of solid solutions and orthorhombic and tetragonal distortions of perovskite-like layers. The temperature dependences of the relative permittivity 𝜀/𝜀o(T) are measured. It was found that the change in the phase transition temperature — Curie temperature TC synthesized Aurivillius phases Bi7−xNd2xTi4NbO21 (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) has a close to linear dependence on the change in the parameter x. The activation energies of charge carriers in different temperature ranges were calculated. It was found that three clearly defined temperature ranges with different activation energies can be distinguished, which is associated with the different nature of charge carriers in the studied solid solutions of the perovskite type. The effect of substitution of Nd3+ ions for Bi3+ ions is investigated.The electrophysical and structural characteristics of bismuth titanate oxides of a number of phases of solid solutions of the Aurivillius phases Bi7−2xNd2xTi4NbO21 (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) having a layered structure of the perovskite type have been investigated. According to the XRD data, all studied compounds are single-phase and have a mixed-layer structure of Aurivillius phases (m = 2.5) with a rhombic crystal lattice (space group I2cm, Z = 2). A relationship has been established between changes in the chemical composition of solid solutions and orthorhombic and tetragonal distortions of perovskite-like layers. The temperature dependences of the relative permittivity 𝜀/𝜀o(T) are measured. It was found that the change in the phase transition temperature — Curie temperature TC synthesized Aurivillius phases Bi7−xNd2xTi4NbO21 (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) has a close to linear dependence on the change in the parameter x. The activation energies of charge carriers in different temperature ranges were calculated. It was found that three clearly defined temperature ranges with different activation energies can be distinguished, which is associated with the different nature of charge carriers in the studied solid solutions of the perovskite type. The effect of substitution of Nd3+ ions for Bi3+ ions is investigated.