The work is focused on the synthesis of a solid solution in the system (1-X) $\mathrm{Pb}_{2} \mathbf{M g W O}_{6}+\left(\mathrm{X}_{2}\right) \mathrm{Pb}_{3} \mathrm{Fe}_{2} \mathbf{W O}_{9}$, where $\mathrm{X}=0.2; 0.4; 0.6; 0.8; 1$; doped with Li 2 CO 3 using high-energy mechanochemical activation and annealing in the temperature range of $600-900{ }^{\circ} \mathrm{C}$. The addition of iron was made in order to investigate the effect on the structural properties of the crystal lattice and the formation of the solid solution. Mechanochemical activation is a promising technique for preparing materials for producing piezoceramic composites. During the activation process, mixing, grinding, defect formation, and the creation of new active surfaces in the powdered materials take place. This allows for the possibility of obtaining the desired compound during the activation process, thus reducing the time required for synthesis and the temperature needed for subsequent annealing.Compressed samples were examined before and after heat treatment using X-ray phase analysis and scanning electron microscopy. The main findings are presented in this paper. Ceramics with a cubic structure and space group Fm3m or Pm3m were obtained and had a density that was $95 \%$ of the theoretical value. The research is of a fundamental nature and aims to study and obtain materials with predetermined properties for future use in various fields of engineering and technology. Specifically, for the production of vibration sensors, which will have a wide range of applications in the electrical power industry, microelectronics, and electrical engineering.

Bi0.6Nd0.4Fe0.5M0.5O3 (M - Mn, Cr) compositions with perovskite structure were fabricated by a high-pressure synthesis. Mossbauer studies have shown that doping with Nd does not change substantially Neel temperature values of Bi0.6Nd0.4 Fe0.5M0.5O3 (M - Cr, Mn) compositions. However, the Fe3+ and Mn3+ ions seem to be inhomogeneously distributed in the crystal lattice and form Fe-poor and Fe-rich regions. Similar result was obtained by us earlier for Bi(Fe1-xCrx)O-3 solid solution. Both compositions studied exhibit a giant dielectric response in a wide temperature range. The giant dielectric response seems to be due to the relaxation of electrons or polarons trapped by oxygen vacancies.

Iron-enriched ferroelectrics are of particular interest as piezoactive components of piezoelectric-ferrite ME ceramics. This is due to the phase composition similarity and the reduction of expected interfacial doping effects during high-temperature calcination. This idea seems attractive, but laborious due to the significantly limited number of possible piezoelectric-ferrite combinations. Therefore, there is practically no data on such systems in the literature. ME composite ceramics based on the highly efficient Fe-containing Pb(Fe0.5Nb0.5)(0.935)Ti0.065O3 (PFNPT) ferroelectric has been studied. (100-& khcy;) wt.% Pb(Fe0.5Nb0.5)(0.935)Ti0.065O3 (PFNPT) + & khcy; wt.% Ni0.9Co0.1Cu0.1Fe1.9O4-d (NCCF) composite systems has been obtained by the solid-state method at 1050 degrees C, with no foreign phases. The specimens densities amounted to similar to 80% of the theoretical. It has been shown that the ME conversion efficiency and other composites properties are significantly influenced by the PFNPT precursor pre-treatment method. The maximum value of the ME coefficient Delta Epsilon/Delta Eta = 75 mV/(cm Oe) has been observed for specimens with x = 50-60 made from PFNPT powder with the addition of Li2CO3. An increase in the ME composites sintering temperature to 1150 degrees C leads to the formation of Pb2Nb2O7 foreign phase with a pyrochlore structure along the grain boundaries. The ME coefficient Delta Epsilon/Delta Eta does not exceed 15 mV/(cm & sdot;Oe). There is an threefold decrease in the composites piezoelectric parameters (piezoelectric coefficients d(ij), g(ij)), as well as in their magnetic properties (magnetizations M-S, M-R) due to piezophase degradation, which is presumably associated with a change in the cations distribution over A and B sublattices of the spinel structure.

X-ray absorption spectroscopic (XAS) and Mössbauer investigations have been carried out to obtain information on the local environment of Fe ions in Pb2FeSbO6 (PFS) samples with different degree of the Fe3+ and Sb5+ ordering. Analysis of Mössbauer spectra shows, that the fraction of doublet component in the spectrum of the disordered PFS sample is significantly larger, than that of the ordered one, however singlet component still persists, indicating the presence of the compositionally ordered regions. The Fe K-spectrum absorption for the ordered PFS sample exhibits the lowest pre-edge intensities, indicating that Fe position is close to the oxygen octahedron center. The higher amplitude of this peak for the disordered sample provides evidence for structural distortions, involving Fe displacement off the octahedra centers. Additional support to this conclusion provides the structure of absorption spectra, which gave substantially higher Debye-Waller factor of Fe–O shell for disordered sample as compared to the ordered one.

Temperature and field dependences of dielectric permittivity epsilon and unipolar electric field-induced strain S of the 0.675Pb(Mg1/3Nb2/3)O-3-0.325PbTiO(3) ceramics have been studied in the 25 & mldr;200 degrees C range. Temperature dependences of both dielectric permittivity and converse piezoelectric modulus d*(33) show anomalies corresponding to phase transitions between rhombohedral (monoclinic), tetragonal, and cubic phases. Based on the data of dielectric and field-induced strain studies, the E,T-phase diagram is plotted. The possible critical behavior of converse piezoelectric modulus d*(33) and its correlation with the position of the known critical point in the E,T-phase diagram of PMN-xPT system are discussed.

Single phase NaNb1−xMnxO3 (NMn) with x = 0.00−0.06 ceramics were synthesized using solid state reaction technique at 1150 °C sintering temperature. The Rietveld refinement of XRD patterns of NMn ceramics confirms the orthorhombic phase symmetry with Pbma space group. The field emission scanning electron microscopy (FE-SEM) reveals that grains become denser and larger with doping. The dielectric constant (ϵ′) and tangent loss (tan δ) study has been done at room temperature to 500 °C over a wide frequency in both cooling and heating mode. The anomaly at high temperature region in temperature dependent dielectric constant (ϵ′) plot in both thermal cycle attributes to the P(AFE)-R(AFE) polymorphic phase transition. The relaxor nature of the studied samples strongly depends on dopant concentration and applied field. The impedance analysis reveals negative temperature coefficient of resistance (NTCR) behaviour of material. The Nyquist study suggests the non-Debye characteristic of the dielectric relaxation in NMn ceramics.

The synthesis of barium and strontium stannates in the process of decomposition of hydrothermally obtained precursors has been investigated. It was found that endothermic weight loss during the synthesis of barium stannate occurs in two stages, whereas during the synthesis of strontium stannate it occurs in one stage. From the summary of the results of thermogravimetric analysis, X-ray diffraction, and Mössbauer spectroscopy, the composition and local structure of X-ray amorphous phases are proposed. It is shown that the improvement of the crystal structure of the perovskite phases of MSnO3 (M = Ba, Sr) and the symmetry of the local environment of 119Sn continues up to high temperatures (1250-1500 °C) and is associated with the elimination of defects in the anion sublattice. The photocatalytic activity of hydrothermal phases MSn(OH)6 and their thermolysis products has been studied and was found not to be directly related to the specific surface area of the photocatalysts. The degradation of rhodamine B (RhB) occurs during the "dark" stages of catalysis due to the interaction of the dye with reactive oxygen species (mainly singlet oxygen). At the first stage, the decomposition of the RhB photochromic system is observed, whereas at the final stage of bleaching the dye is deethylated.

NaNb1-xZrxO3 (NZr) ceramics with 0<x<0.15 are prepared via solid-state reaction route. Structural, microstruc-tural, and electronic state investigations of NZr samples were performed using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and X-ray photoelectron spectroscopy (XPS), respectively. Rietveld refinement reveals that NZr samples crystallize in the orthorhombic phase similar to room temperature Pbma phase of NaNbO3. Minor quantities of ZrO2 are detected for higher NZr-composition, which suppress the grain growth of NZr ceramics. XPS reveals that small amount of Zr substitution in NaNbO3 also creates an ambiance of unbalanced charge neutrality. The dielectric characteristics of NZr samples are investigated from -190 to 450 degrees C temperature range in frequency window 1 KHz-1 MHz for both the heating and cooling cycles. A clear thermal hysteresis loop is obtained in each composition and the observed anomaly corresponds to P (AFE) -R (AFE) polymorphic phase transition. As x grows, "' (T) becomes more dispersive and strongly depend on applied field. The activation energy obtained from the analysis of Arrhenius relation indicates that the oxygen vacancies are responsible for conduction process of the material. Impedance analysis confirms the NTCR behavior and non-Debye relaxation of the material.

The temperature dependencies of second harmonic generation (SHG) in (1-x)PMN-xPSN solid solutions (x = 1, 0.35, 0.23, 0.1, 0) are measured. Presence of SHG signal in centrosymmetric phase in all samples studied is demonstrated. It indicates asymmetric regions in the centrosymmetric phase. In PMN crystal (x = 0) in the centrosymmetric phase, SHG temperature dependence follows deviations of strain and refractive index from their high-temperature dependencies, which are determined by random electric fields in local polar regions. In the intermediate temperature range, where macroscopic spontaneous polarization disappears, SHG signal is caused by relatively large and long-lived polar asymmetric regions.

Perovskite materials based on BiFeO 3 ‐PbTiO 3 (BFPT) solid solutions are promising for various applications thanks to the extremely large spontaneous polarization ( P s ) and existence of multiferroic morphotropic phase boundary. For applications in piezoelectric and memory devices, complete switching of P s is needed, which is hard to achieve practically. In this work, a simple modified mixed‐oxide reaction method is developed allowing to prepare Dy‐ and Sm‐modified BFPT ceramics with significantly improved properties. The MPB compositions demonstrate well‐saturated ferroelectric hysteresis loops with large switchable remanent polarization of 60 µC cm −2 and enhanced piezoelectric properties with a large‐signal piezoelectric coefficient d 33 * = 214 pm V −1 and a direct piezoelectric coefficient d 33 = 128 pC N −1 , which is one and a half times larger than the best d 33 value reported for the BFPT ceramics so far. The Curie temperature reaches 539 °C, suggesting a potential for high‐temperature applications. The domain structure is studied by piezoresponse force microscopy. It is found that the enhanced dielectric/piezoelectric properties are mainly due to polarization rotation/extension (intrinsic) mechanism, while the extrinsic contributions of the interphase and domain walls are virtually absent. The strategies for improvement of properties of BFPT and related materials are proposed.

Ceramic samples of barium ferrostannate BaFe1/2Sn1/2O3-delta have been prepared by the sol-gel and hydrothermal synthesis methods. To reduce the number of oxygen vacancies, annealing in oxygen has been performed. The heat capacity, magnetization, Mossbauer and dielectric spectroscopy data point to the appearance of antifer-romagnetic ordering below similar to 55 K followed by further spin glass magnetic ordering below 15 K. The giant dielectric response seems to be due to the relaxation of electrons trapped by oxygen vacancies. Comparison of the Fe K-edge X-ray absorption spectra of BaFe1/2Sn1/2O3-delta confirmed substantial difference from those of the similar stoichiometric BaFe1/2Nb1/2O3 perovskite.

Two ferroelectric phase transitions are observed in the PbFe0.5Nb0.5O3 crystal. The first is between the cubic and tetragonal phase, the second is between the tetragonal and monoclinic phases. To describe phase transitions and emerging phases, a statistical model is proposed, based on the composition of two multi-minimum models --- a six-minima model for the Pb cation and an eight-minima model for the Nb cation. Adjusting the model parameters, makes it possible to reproduce all the characteristic features of the thermodynamic behavior of the crystal. The most interesting is the formation of a ferroelectric, complexly ordered monoclinic phase with Cm symmetry. It is shown that the mentioned monoclinic phase arises due to the fact that the first-order phase transition to the rhombohedral ferroelectric phase occurs in the presence of an "external field" of tetragonal symmetry. The contribution of the subsystems of Pb and Nb cations to the features of the dielectric and structural properties of the crystal is estimated. Keywords: ferroelectric relaxors, phase transitions, multiminima models, ferroelectric monoclinic phase.

Dissipation of the charge injected into the 0.5 x 0.5 mu m(2) surface areas of [100] - oriented 500 nm-thick epitaxial NaNbO3 film was studied by Kelvin Probe Force Microscopy. The elliptical area of the electric potential spot dissipates during similar to 4 divided by 4.5 h via leakage through the film surface and substrate. At the final stage, a small negative surface potential clearly manifests itself in the places of the surface blocks as existed before injection. This inherent potential explains previously found unipolarity of this film. The charge diffusion coefficient and mobility of charge carriers are estimated.

The B-site-doping method of barium titanate (BaTiO3) is one of the promising route to prepare lead-free materials with enhanced dielectric and piezoelectric properties. Lead-free (Ba0.85Ca0.15)(Zr0.1-xSnxTi0.9)O-3 [BCZT:Sn] (x = 0, 0.02, 0.04 and 0.06) ceramics were synthesized using the sol-gel method. The effects of Sn content on the energy-storage performance and electric conduction mechanisms of BCZT ceramic were systematically investigated. The energy storage performance investigation showed that the recoverable energy storage has been enhanced with Sn doping rate, the composition doped x = 0.02 (BCZT: 2Sn) depicted the highest recoverable energy density and efficiency (W-rec = 19 mJ/cm(3), eta = 81.65%). The electrical properties of the BCZT:Sn ceramics were investigated using the impedance spectroscopy technique at temperature range of 25-450 degrees C. The net impedance of the samples showed a significant enhancement as the Sn content increases, owing to the lattice distortion created by the relative difference in the radius of Sn4+ and Zr4+ and different outer electronic shells. The AC conductivity was measured and analyzed as a function of frequency and temperature. Obtained activation energy values were associated with possible conduction mechanisms. (C) 2021 Elsevier Ltd. All rights reserved.

Ceramic samples of BiFeO3-based perovskite solid solutions with the highly ordered complex perovskites [Formula: see text][Formula: see text]O3(PFS) and [Formula: see text][Formula: see text]O3 (SFS) were obtained using high-pressure synthesis at 4–6 GPa. Mössbauer studies revealed that BiFeO3-SFS compositions are characterized by a larger compositional inhomogeneity as compared to BiFeO3-PFS ones. In line with this result, concentration dependence of the magnetic phase transition temperature [Formula: see text] for BiFeO3-SFS compositions is close to the [Formula: see text] dependence for BiFeO3solid solution with disordered perovskite [Formula: see text][Formula: see text]O3(PFN). In contrast to this [Formula: see text] dependence for BiFeO3-PFS compositions nicely follows the theoretical [Formula: see text] dependence calculated for the case of the ordered distribution of Fe[Formula: see text] and non-magnetic Sb[Formula: see text] ions in the lattice (chemical ordering).

Methods of changing the compositional (chemical) ordering degree S of B' and B" cations in PbB1/2'B-1/2"O-3 perovskites and some BiFeO3-PbFe1/2B1/2"O-3 solid solutions and the effect of such ordering/disordering on their dielectric and magnetic properties are discussed. High-energy mechanical activation appears to be a very effective method of varying the temperatures of ferroelectric and magnetic phase transitions in complex perovskites. To explain the results obtained, one needs to take into account the changes not only of the long-range ordering of B' and B" ions, but also of the short range ordering.

0.5BiFeO(3)-0.5Pb(1-x)Sr(x)TiO(3) (0 <= x <= 1) solid solution compositions were synthesized using solid phase reactions route from high-purity oxides. Mossbauer studies showed that for 0.5BiFeO(3)-0.5PbTiO(3) (x = 0) the magnetic phase transition temperature T (M) value was about 130 K. Substitution of Sr for Pb led to a dramatic decrease in T (M), though the Fe content did not change with x and for 0.5BiFeO(3)-0.5SrTiO(3) (x = 1) T (M) was only approximate to 20 K. This dramatic difference in T (M) values seems to be due to additional contribution of the magnetic superexchange between Fe3+ ions via the empty 6p states of Bi3+ and Pb2+ ions to the overall superexchange.

A. V. Pavlenko, 2 D. V. Stryukov, M. V. Vladimirov, A. E. Ganzha, S. A. Udovenko, Anjana Joseph, Janaky Sunil, Chandrabhas Narayana, R. G. Burkovsky, I. P. Raevski, and N. V. Ter-Oganessian ∗ Institute of Physics, Southern Federal University, 344090 Rostov-on-Don, Russia Southern Scientific Center, Russian Academy of Sciences, 344006 Rostov-on-Don, Russia Peter the Great Saint-Petersburg Polytechnic University, 195251 St. Petersburg, Russia Jawaharlal Nehru Centre for Advanced Scientific Research, 560064 Bangalore, India (Dated: December 10, 2021)