In this study, the double-layered Aurivillius phases CaBi2Ta2O9 (CBT) and PbBi2Ta2O9 (PBT) were prepared through a hydrothermal route with NaOH as a mineralizer. XRD analysis confirmed that the CBT and PBT compounds were successfully formed and adopted an orthorhombic crystal structure with an A21am symmetry. Le Bail refinements of XRD data indicated that the unit cell volume of CBT was smaller than PBT and is associated with the smaller ionic radius of Ca2+ compared to Pb2+. The surface morphology of both samples, as determined using SEM, demonstrated plate-like grains with anisotropic grain growth. It was found that the different ionic radii of A-site cations (Ca2+ and Pb2+) strongly affected the structural, optical and electrical properties of the Aurivillius phase. The occupation of smaller Ca2+ cations induced a higher structural distortion, which resulted in higher bandgap (Eg) energy and ferroelectric transition temperature (Tc) of CBT, compared to those of PBT.In this study, the double-layered Aurivillius phases CaBi2Ta2O9 (CBT) and PbBi2Ta2O9 (PBT) were prepared through a hydrothermal route with NaOH as a mineralizer. XRD analysis confirmed that the CBT and PBT compounds were successfully formed and adopted an orthorhombic crystal structure with an A21am symmetry. Le Bail refinements of XRD data indicated that the unit cell volume of CBT was smaller than PBT and is associated with the smaller ionic radius of Ca2+ compared to Pb2+. The surface morphology of both samples, as determined using SEM, demonstrated plate-like grains with anisotropic grain growth. It was found that the different ionic radii of A-site cations (Ca2+ and Pb2+) strongly affected the structural, optical and electrical properties of the Aurivillius phase. The occupation of smaller Ca2+ cations induced a higher structural distortion, which resulted in higher bandgap (Eg) energy and ferroelectric transition temperature (Tc) of CBT, compared to those of PBT.

Erbium-doped barium titanate (BaTiO3:Er) xerogel film with a thickness of about 500 nm was formed on the porous strontium titanate (SrTiO3) xerogel film on Si substrate after annealing at 800∘C or 900∘C. The elaborated structures show room temperature upconversion luminescence under 980 nm excitation with the photoluminescence (PL) bands at 523, 546, 658, 800 and 830 nm corresponding to 2H11/2→4I15/2, 4S3/2→4I15/2, 4F9/2→4I15/2 and 4I9/2→4I15/2 transitions of trivalent erbium. Raman and X-ray diffraction (XRD) analysis of BaTiO3:Er\porous SrTiO3\Si structure showed the presence of perovskite phases. Its excellent up-conversion optical performance will greatly broaden its applications in perovskite solar cells and high-end anti-counterfeiting technologies.Erbium-doped barium titanate (BaTiO3:Er) xerogel film with a thickness of about 500 nm was formed on the porous strontium titanate (SrTiO3) xerogel film on Si substrate after annealing at 800∘C or 900∘C. The elaborated structures show room temperature upconversion luminescence under 980 nm excitation with the photoluminescence (PL) bands at 523, 546, 658, 800 and 830 nm corresponding to 2H11/2→4I15/2, 4S3/2→4I15/2, 4F9/2→4I15/2 and 4I9/2→4I15/2 transitions of trivalent erbium. Raman and X-ray diffraction (XRD) analysis of BaTiO3:Er\porous SrTiO3\Si structure showed the presence of perovskite phases. Its excellent up-conversion optical performance will greatly broaden its applications in perovskite solar cells and high-end anti-counterfeiting technologies.

In this paper, the results of experimental study of dispersion characteristics of complex electromechanical parameters of ferroelectrically “hard” porous piezoceramics based on PZT composition were presented. Experimental samples of porous piezoceramics were fabricated using a modified method of burning-out a pore former. The complex constants of porous piezoceramics with relative porosity 16% and their frequency dependences were measured using the piezoelectric resonance analysis method. As a result of experimental studies, regions of elastic, piezoelectric and electromechanical dispersion, characterized by anomalies in the frequency dependences of the imaginary and real parts of the complex constants of porous piezoelectric ceramics were found. It was revealed also that the microstructural features of porous piezoceramics determine the character of frequency dependences of complex electromechanical parameters of porous piezoelectric ceramics. In conclusion, the microstructural and physical mechanisms of electromechanical losses and dispersion in porous piezoceramics were discussed.In this paper, the results of experimental study of dispersion characteristics of complex electromechanical parameters of ferroelectrically “hard” porous piezoceramics based on PZT composition were presented. Experimental samples of porous piezoceramics were fabricated using a modified method of burning-out a pore former. The complex constants of porous piezoceramics with relative porosity 16% and their frequency dependences were measured using the piezoelectric resonance analysis method. As a result of experimental studies, regions of elastic, piezoelectric and electromechanical dispersion, characterized by anomalies in the frequency dependences of the imaginary and real parts of the complex constants of porous piezoelectric ceramics were found. It was revealed also that the microstructural features of porous piezoceramics determine the character of frequency dependences of complex electromechanical parameters of porous piezoelectric ceramics. In conclusion, the microstructural and physical mechanisms of electromechanical losses and dispersion in porous piezoceramics were discussed.

Solid solutions of the composition Ba1−x−y(Mg, Ln)xSryTiO3 (x = 0.01; 0.025; 0.04; y = 0.20; 0.50; 0.80; Ln = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tu, Yb) were prepared by two-stage solid-phase synthesis followed by sintering using conventional ceramic technology. The influence of rare-earth elements on the microstructure of the prepared ceramic samples was investigated. It was found that regardless of the type of modifiers introduced, the grain landscape of the studied solid solutions with different amounts of SrTiO3 is refined (in the initial system, the average grain size, d̄, at x = 0.20 is 6 μm; at x = 0.50 is 4 μm; at x = 0.80 is 18 μm) to crystallite sizes not exceeding (2-3) μm, and compacted. The using of mechanical activation procedures leads to an even greater decrease in the size and an increase in the density of ceramics. The increasing in the concentration of modifiers in each group (within the considered range of dopant variation) against the background of such a fine-grained structure has little effect on the dynamics of changes in d̄. It is concluded that it is advisable to use the data obtained in the development of functional materials based on BST/(Mg, Ln) and devices with the participation of these compositions.Solid solutions of the composition Ba1−x−y(Mg, Ln)xSryTiO3 (x = 0.01; 0.025; 0.04; y = 0.20; 0.50; 0.80; Ln = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tu, Yb) were prepared by two-stage solid-phase synthesis followed by sintering using conventional ceramic technology. The influence of rare-earth elements on the microstructure of the prepared ceramic samples was investigated. It was found that regardless of the type of modifiers introduced, the grain landscape of the studied solid solutions with different amounts of SrTiO3 is refined (in the initial system, the average grain size, d̄, at x = 0.20 is 6 μm; at x = 0.50 is 4 μm; at x = 0.80 is 18 μm) to crystallite sizes not exceeding (2-3) μm, and compacted. The using of mechanical activation procedures leads to an even greater decrease in the size and an increase in the density of ceramics. The increasing in the concentration of modifiers in each group (within the considered range of dopant variation) against the background of such a fine-grained structure has little effect on the dynamics of changes in d̄. It is concluded that it is advisable to use the data obtained in the development of functional materials based on BST/(Mg, Ln) and devices with the participation of these compositions.

In this paper, a comprehensive study of microstructure/properties interrelations for porous piezoceramics based on PZT composition was performed. Experimental samples of porous piezoceramics were fabricated using a modified method of burning-out a pore former. Porosity dependencies of elastic, dielectric, piezoelectric and electromechanical coefficients of the porous ceramics in the relative porosity range 0-50% were obtained and analyzed. As a result of microstructure analysis, it was found that at any connectivity type (3–0, 3–3) and porosity up to 50% the real structures of porous piezoceramics were close to the matrix medium structure with continuous piezoceramic skeleton. It was also revealed that the microstructural features of porous piezoceramics define the character of the dependences of the dielectric, piezoelectric and electromechanical properties of porous piezoelectric ceramics on porosity. In conclusion, microstructure/properties interrelations, as well as new applications of porous piezoceramics were discussed.In this paper, a comprehensive study of microstructure/properties interrelations for porous piezoceramics based on PZT composition was performed. Experimental samples of porous piezoceramics were fabricated using a modified method of burning-out a pore former. Porosity dependencies of elastic, dielectric, piezoelectric and electromechanical coefficients of the porous ceramics in the relative porosity range 0-50% were obtained and analyzed. As a result of microstructure analysis, it was found that at any connectivity type (3–0, 3–3) and porosity up to 50% the real structures of porous piezoceramics were close to the matrix medium structure with continuous piezoceramic skeleton. It was also revealed that the microstructural features of porous piezoceramics define the character of the dependences of the dielectric, piezoelectric and electromechanical properties of porous piezoelectric ceramics on porosity. In conclusion, microstructure/properties interrelations, as well as new applications of porous piezoceramics were discussed.

The comparative analysis of the dielectric properties of bismuth-containing pyrochlores with different manifestation of atomic order/disorder was carried out. We examined the dielectric properties (including behavior in electric fields) of two pyrochlore compounds: BZN (presumably a composition close to Bi1.5Zn0.5Nb1.5O6.5) ceramics with chemical disorder in both A and B cation sublattices and Bi2Ti2O7 single crystal with fully chemical ordered structure. The fundamental differences between the dielectric properties of the BZN ceramics and Bi2Ti2O7 single crystal were shown. In particular, in the dielectric relaxation behavior (which cannot be described via Arrhenius law in the Bi2Ti2O7) or in the influence of the electric fields on the dielectric permittivity (splitting of the field-cooled and zero-field-cooled behaviors was observed for Bi2Ti2O7 below estimated freezing temperature). The results of this study highlights the special role of Bi2Ti2O7 as a candidate material for studying aspects of geometric frustration related with pyrochlore structure in non-magnetic medium and specifies the future directions of research.The comparative analysis of the dielectric properties of bismuth-containing pyrochlores with different manifestation of atomic order/disorder was carried out. We examined the dielectric properties (including behavior in electric fields) of two pyrochlore compounds: BZN (presumably a composition close to Bi1.5Zn0.5Nb1.5O6.5) ceramics with chemical disorder in both A and B cation sublattices and Bi2Ti2O7 single crystal with fully chemical ordered structure. The fundamental differences between the dielectric properties of the BZN ceramics and Bi2Ti2O7 single crystal were shown. In particular, in the dielectric relaxation behavior (which cannot be described via Arrhenius law in the Bi2Ti2O7) or in the influence of the electric fields on the dielectric permittivity (splitting of the field-cooled and zero-field-cooled behaviors was observed for Bi2Ti2O7 below estimated freezing temperature). The results of this study highlights the special role of Bi2Ti2O7 as a candidate material for studying aspects of geometric frustration related with pyrochlore structure in non-magnetic medium and specifies the future directions of research.

This paper reports the impact of the laser pulse repetition frequency on growth processes, morphological and electro-physical parameters of nanocrystalline LiNbO3 thin films obtained by the pulsed laser deposition technique. It was found that the nucleation process in LiNbO3 films could controllably change by increasing the laser pulse repetition frequency. The film obtained at the repetition frequency of 4 Hz consists of local islands and clusters with a diameter of 118.1 ± 5.9 nm. Nanocrystalline films, grown at the repetition frequency of 10 Hz, possess a continuous granular structure with a grain diameter of 235 ± 11.75 nm. Achieved results can be used for the development of promising “green” energy devices based on lead-free piezoelectric energy harvesters.This paper reports the impact of the laser pulse repetition frequency on growth processes, morphological and electro-physical parameters of nanocrystalline LiNbO3 thin films obtained by the pulsed laser deposition technique. It was found that the nucleation process in LiNbO3 films could controllably change by increasing the laser pulse repetition frequency. The film obtained at the repetition frequency of 4 Hz consists of local islands and clusters with a diameter of 118.1 ± 5.9 nm. Nanocrystalline films, grown at the repetition frequency of 10 Hz, possess a continuous granular structure with a grain diameter of 235 ± 11.75 nm. Achieved results can be used for the development of promising “green” energy devices based on lead-free piezoelectric energy harvesters.

Pb0.96Sr0.04(Zr,Ti)0.7(Zn1/3Nb2/3)0.3O3 (PZN–PZT) piezoceramics with various Zr/Ti ratios and Li2CO3 sintering aid were sintered at 900∘C by the solid-state reaction route. The samples with different Zr/Ti ratios were compared according to microstructure, phase structure, piezoelectricity, ferroelectricity, and dielectric relaxation. The Zr/Ti ratio in the PZN–PZT ceramics greatly affects the electrical properties. The Zr/Ti ratio affects the proportion between the rhombohedral and tetragonal phases and also affects the grain size. The PZN–PZT ceramics with the Zr/Ti ratio of 53:47 have the largest grain size and have optimized piezoelectric properties (kp = 0.58, d33 = 540 pC/N, and TC = 250∘C). The larger the grain size, the lesser the grain boundary, the easier the domain wall motion, and the better the piezoelectric properties. The PZT ceramic with Zr/Ti ratio of 53:47 locates the morphotropic phase boundary (MPB) region which is one of the key factors for the high piezoelectric properties of the PZT.Pb0.96Sr0.04(Zr,Ti)0.7(Zn1/3Nb2/3)0.3O3 (PZN–PZT) piezoceramics with various Zr/Ti ratios and Li2CO3 sintering aid were sintered at 900∘C by the solid-state reaction route. The samples with different Zr/Ti ratios were compared according to microstructure, phase structure, piezoelectricity, ferroelectricity, and dielectric relaxation. The Zr/Ti ratio in the PZN–PZT ceramics greatly affects the electrical properties. The Zr/Ti ratio affects the proportion between the rhombohedral and tetragonal phases and also affects the grain size. The PZN–PZT ceramics with the Zr/Ti ratio of 53:47 have the largest grain size and have optimized piezoelectric properties (kp = 0.58, d33 = 540 pC/N, and TC = 250∘C). The larger the grain size, the lesser the grain boundary, the easier the domain wall motion, and the better the piezoelectric properties. The PZT ceramic with Zr/Ti ratio of 53:47 locates the morphotropic phase boundary (MPB) region which is one of the key factors for the high piezoelectric properties of the PZT.