Hysteresis, tilt angle, spontaneous polarization and Electro-Clinic effect were investigated for SmC* exhibited by a liquid crystal dimer, viz., 11OBA:M*SA:ABO11 with chiral center on spacer moiety. Primary order parameter tilt angle theta(T) growth agreed with Critical field model prediction, while secondary order parameter spontaneous polarization growth P-s(T) agreed with Mean field predictions. Order parameter exponents inferred prevalence of pair-wise correlation for dipole stabilization of order director fluctuations regarding primary order parameter. Secondary order parameter critical exponent defended long range dipole ordering. The tilt order parameter growth and its moderate saturated value inferred a relatively small viewing angle for a device. Small hysteresis area indicated limited storage capacity. Comparable EC response identified in SmC* phase. Relatively large Electro-Clinic coefficient realized for higher fields at higher temperatures for its utility in devices. EC effect is compared with that reported other chiral SmC LC phases. Magnitude and trends of hysteresis, tilt angle and polarization are presented, discussed, analyzed and addressed in terms of interplay between P and parity. Integrated view inferred strong influence of spacer based chiral center in the LC dimer.
Dielectric and impedance spectroscopy (20 Hz-2 MHz) of Bridgman-grown In2Se2.Sb-7(0).(3) crystals reveals that Sb doping significantly alters electrical properties. Findings include strong low-frequency electrode polarisation, non-Debye relaxation, and conductivity transitioning from DC to correlated barrier hopping. The electric modulus formalism resolved two distinct grain and grain-boundary relaxation processes, which were not separable in the impedance data. These insights highlight Sb's role in modifying the polarisation dynamics and charge transport in In2Se3 for advanced optoelectronic applications.
Based on 0.655PMN-0.345PT piezoelectric ceramics, a novel piezoelectric vibration actuator was proposed. The model of the actuator was designed and fabricated by the manufacturing process. The grains of the PMN-PT ceramics were investigated by microstructure analyses. The performances of the proposed actuator were studied. The results showed that the actuator achieved a charge sensitivity of 65.9 pC/g at room temperature, a sensitivity deviation of 2.792% in the range of 10 Hz similar to 3000 Hz, a transversal sensitivity ratio of 0.7%. The highest sensitivity deviation of the actuator reached 0.088%, which meet the application requirements. Compared with the other three actuators on the market, the proposed actuator got a good performance.
In this work, we theoretically study the magnetic phase transitions in the solid solutions (1-x)BiFeO3 - xAFe(1/2)M(1/2)O(3) (A = Pb, Ba, Ca, Sr; M = Nb, Sb). We first calculate the magnetic exchange constants using the density functional theory, which are then used in Monte Carlo calculations. We obtain the dependence of magnetic phase transition temperature on x for different cases of the distribution of Fe and M atoms in the B-sublattice of the perovskite structure, i.e. purely statistical distribution, local clustering, and local ordering. Comparison with the experimental data may suggest the change in local arrangement of atoms above x approximate to 0.7 for some compounds.
Temperature and field dependences of dielectric permittivity epsilon and unipolar electric field-induced strain S of the textured 0.675Pb(Mg1/3Nb2/3)O3-0.325PbTiO3 ceramics have been studied in the 25 degrees C & 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 is discussed.
The aim of the research is to develop a technology of ceramic piezoelectric materials which & scy;an be used in thermo cyclic mode at temperatures above 280 degrees C. This technology has been developed for the piezoelectric ceramics based on (1-x)PbTiO3 - xBa0.85Ca0.15Ti0.90Zr0.10O3 (x = 0.15-0.45). The use of low-temperature (380-400 degrees C) synthesis of ultrafine phase powders and stepwise firing of press blanks make it possible to produce densely packed ceramics with grain diameter of 1 to 2 mu m. It has been established that the mole fraction of Ba0.85Ca0.15Ti0.90Zr0.10O3 in the composition increases epsilon & Tcy;33/epsilon 0 from 620 to 1070, and increases d33 from 165 to 330 pC/N. Thermal cycling of piezoelements based on phases with x = 0.2-0.25 (8 cycles: heating to 350 degrees C - cooling) reduces d33 only by 6-8%, and epsilon & Tcy;33/epsilon 0 - by about 5%.
The dielectric properties of layered two-component structures consisting of a dielectric of strontium titanate SrTiO3 and a ferroelectric of lead titanate PbTiO3 are investigated. In these structures, a ferroelectric phase transition occurs at a temperature of 544 & ring;& Scy;, which significantly exceeds the phase transition temperature of ferroelectric PbTiO3. This effect may be due to the very small thickness of the PbTiO3 ferroelectric layer and the influence of the dielectric SrTiO3.
Two types of porous matrices with the surface of channels (pores) modified by carbon, titanium oxide and aluminum oxide have been prepared on the basis of nanoporous sodium borosilicate glasses with average pore diameters of 7 nm (PG7) and similar to 30 nm (WPG). It has been shown that all modifiers in these glasses are in an amorphous state. The effect of modification on the spatial and fractal characteristics of the produced porous matrices has been studied by small-angle X-ray scattering. It has been shown that the introduction of modifiers significantly affects the spatial organization of the pore space in porous matrices based on PG7 and practically does not affect it in WPG. The characteristic sizes and shapes of nanoparticles of modifiers (C, TiO2, Al2O3) formed in the manufactured porous matrices based on PG7 were determined.
In this work we synthesize (1-x)PbMg1/3Nb2/3O3 - xLaMg(2/3)Nb(1/3)O(3) (x = 0 - 0.15) solid solutions with different degrees of long-range atomic ordering by varying the thermodynamic history of the samples. The dielectric properties show strong dependence on atomic ordering. The emergence of long-range atomic ordering in PbMg1/3Nb2/3O3 upon increasing x is explained by Monte Carlo calculations.
The results of X-ray diffraction analysis, study of their microstructure and magnetodielectric properties of the solid solutions (1-& khcy;)BiFeO3 - x/2PbFe1/2Nb1/2O3 - x/2PbFe2/3W1/3O3 system are presented in this work. The study system has a morphotropic phase transition at room temperature from the rhombohedral to the cubic phase. The change in microstructure is consistent with the changes in the phase diagram, with the greatest densification achieved in morphotropic region and near of them. A weak magnetodielectric effect is detected in the solid solutions ((1-& khcy;)BiFeO3 - x/2PbFe1/2Nb1/2O3 - x/2PbFe2/3W1/3O3 system. The agreement of the results of magnetodielectric responses with relaxation processes occurring in the investigated system is revealed.
Novel 2-2-type composites with two ferroelectric components are put forward, and hydrostatic piezoelectric coefficients d(h)* and g(h)*, and figure of merit d(h)*g(h)* of these composites are studied. Each composite with 2-1-2 connectivity contains the domain-engineered single crystal layers and ferroelectric ceramic/polymer layers. Hydrostatic parameters of the lead-free and lead-containing 2-1-2 composites are compared, and the key role of the single crystal component is highlighted. Due to the high-performance ferroelectric components and orientation effect concerned with the ceramic rods, large hydrostatic parameters d(h)*> 10(-10) C/N, g(h)*similar to 0.1 V(.)m/N and d(h)*g(h)*similar to 10(-11 )Pa(-1) are achieved.
The inhomogeneous distribution of the lateral piezoelectric response and surface potential over a spherulitic perovskite islands is studied. It is shown that the non-uniform distribution of the lateral piezoresponse is associated with the action of radial tensile mechanical stresses acting on the spherulitic island from the low-temperature pyrochlore matrix, as well as the formation of a negative space charge at the interface, leading to the formation of radial (lateral) self-polarization. It is assumed that the inhomogeneous radial distribution of the surface potential of the islands is caused by recrystallization of the perovskite phase.
Ferroelectric and antiferroelectric phase transitions at Curie temperatures, TC, of the multiferroics, along with their magnetic phase transitions at N & eacute;el temperatures, TN, classical ferroelectric and antiferroelectric phase transitions, as well as rotational phase transitions of known perovskite oxides and fluorides ABX3, where X = O or F, at temperatures TR are considered. The goal is to construct the dependences of their TC, TN or TR values on their corresponding interatomic bond strain values, delta AX, and determine how much the areas of changes in delta AX values for phase transitions of every nature separate from each other or where they overlap.
The features of phase transitions in ferroelectrics with incommensurate phases are discussed. The proposal that a second order phase transition from incommensurate to commensurate ferroelectric phase in a bulk material take place in the temperature range (TCl,TCh) is qualitatively consistent with the experiment. It has been shown that the temperature range varies significantly in a thin ferroelectric film, depending on the film thickness and its surface properties.
Results of the X-ray diffraction and scanning electron microscopic analysis of morphological changes in the piezoelectric PZT ceramic surface before and after plasma irradiation are presented. It is shown that repeated exposure to high energy density hydrogen plasma flows leads to a significant change in the structure and elemental composition of the near-surface layer. At the same time, bulk piezoelectric properties of the material change only slightly. The mechanism of surface modification and its relationship with the change/preservation of the basic physical properties of PZT piezoelectric ceramics are discussed.
The results of a study of the structural perfection of crystals and ceramics of lithium niobate and lithium tantalate of various compositions are presented. In solid solutions of the LiNbxTa1-xO3 family with 0.4 <= x <= 0.6, lines were found in the Raman spectra, both of the first (in the range of 150-900 cm-1) and of the second order, located in the range of 900-2000 cm-1. Second-order Raman lines in the range 900-2000 cm-1 were also recorded by us in a number of single-crystals of lithium niobate and tantalate with single and double doping: LiNbO3:Tb(2.24 wt.%), LiTaO3:Cr(0.005 wt.%), LiTaO3:Cr(0.2):Nd(0.45 wt.%), and LiNbO3:Gd(0.003):Mg(0.65). The observed lines in the range of 900-2000 cm-1 are explained as manifestations of overtone processes corresponding to biphonons.
