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A two-dimensional constitutive model, which is based on micromechanical rotation of domains, is presented in this work to demonstrate the non-linear behavior of ferroelectric materials under different loading conditions. A temperature-dependent combined material model that incorporates both phases i.e., tetragonal and rhombohedral phases is embedded into two-dimensional polygonal finite element framework. The developed material model which has easily overcome shortcomings related to tetragonal model and rhombohedral model alone. This model is developed on the morphotropic phase boundary which has produced desired behavior based on macroscopic material parameters. Temperature effects on behavior of combined material model are obtained in the work. Furthermore, polarization rotation test and temperature effects on polarization rotation are also studied in present work. There are numerous studies conducted on ferroelectric materials. All of them incorporate behavior of ferroelectric material confined to specific conditions. Either tetragonal model or rhombohedral model has been used extensively to get the desired behavior based on macroscopic material parameters. This model has some limitations in either satisfying one or another condition related to experiments conducted to study the behavior of ferroelectric materials. The tetragonal material model is capable of producing results with microscopic material properties but in case of macroscopic material parameters the tetragonal model is insufficient to produce the desired behavior for PZT ceramics. The rhombohedral material model is sufficient to produce results based on macroscopic material parameters. Therefore, model is extended by rhombohedral phase, allowing a mixture of both phases with varying quantities inside the grain. Though, rhombohedral model is also not used to that extent. We have developed material model that gives desired behavior and overcomes the hurdles in the existing model. [ABSTRACT FROM AUTHOR]

[(Ba0.85Ca0.15)1-xDyx](Zr0.1Ti0.9)O3 (x mol% Dy-BCZT, x = 0.05, 0.2, 0.5, 1 and 3 mol%) multifunctional lead-free ceramics were prepared by traditional solid-state reaction method, where the influence of Dy doping amount and sintering condition was investigated. All sintered x mol% Dy-BCZT ceramics exhibit pure perovskite structure, large density, and high resistivity, which are affected greatly by Dy doping amount and sintering temperature. The phase structure changes from mainly tetragonal phase to pseudo-cubic phase with the increase of Dy doping amount, and presents irregular change on sintering temperature. Most samples have excellent dielectric, ferroelectric and stain, piezoelectric and fluorescent properties, which can be improved by changing Dy doping amount and tailoring sintering condition. Maximum piezoelectric-fluorescent coupling effect is obtained by selecting composition, optimizing Dy doping amount, and tailoring sintering condition due to morphotropic phase boundary effect and concentration quenching effect, which provides broad application prospect in the field of optoelectronics. [ABSTRACT FROM AUTHOR]

Through a typical solid-state reaction followed by planetary ball milling, ABO3 structured perovskite Bi0.5Na0.5ZrO3 (BNZ) was employed as an additive to create the lead-free piezoceramic composite having compositional formula K0.47Na0.47Li0.06NbO3+(x)Bi0.5Na0.5ZrO3 where x = 0.0 wt% to 0.5 wt%. The prepared composites were characterized with the help of XRD, SEM, and FTIR. The XRD results indicated manifestation of morphotropic phase boundary (MPB), i.e. orthorhombic-tetragonal (O-T) phase boundary, for 0.4 wt% and 0.5 wt%. The SEM pictures revealed the microstructural properties of grain-grain size distribution and the average grain size of the composites. The elemental composition examination using EDAX revealed no foreign element contamination. The FTIR examination verified the development of perovskite, indicating that the BNZ has correctly fused into the KNLN matrix. The DC resistivity (ρdc) behavior was determined from IV and IR curves measured at room temperature together with varied temperature line up from 30 °C to 150 °C and a high dc resistivity ρdc of order ≈ 109 Ω cm was obtained for all the ceramics. The results have been analyzed and the mechanism pertaining to the results has been discussed in the paper. Thus the main idea was to develop a lead-free piezoceramic composite by incorporating Bi0.5Na0.5ZrO3 as an additive and investigating its effect on the above mentioned properties of the composite material. [ABSTRACT FROM AUTHOR]

In the present work, we investigated the effect of BiZn0.5Ti0.5O3 composition on energy storage and electrocaloric properties of lead free (1-x)(0.6Ba(Zr0.2Ti0.8)O3‐0.4(Ba0.7Ca0.3)TiO3)–xBiZn0.5Ti0.5O3 [BZCT-BZ] ceramics by varying the x from 0 to 10%. The x-ray diffraction (XRD) analysis evidences the formation of BZCT-BZ solid solution without any secondary or impurity phase. The peaks splitting at 2θ = ∼ 45° and 66° suggested the co-existence of rhombohedral (R) and tetragonal (T) phases (morphotropic phase boundary) at room temperature for x ≤ 1%. Further, BZCT-BZ ceramics with x > 1% exhibited pseudocubic nature. The ferroelectric hysteresis loop confirms relaxor behavior and the decrease in remanent polarization with increase of BZ content is explained based on the back switching calculations. The BZCT-BZ ceramics as function of BZ composition gave the optimum recoverable energy density of 197 mJ/cm3 and an efficiency of 92% at an applied field of 45 kVcm−1. Such an exceptionally high energy storage efficiency is attributed to the enhanced relaxor behavior and superior back switching capability. Further, the values of electrocaloric temperature change and responsivity are found to be 0.67 K at 45 kV/cm and 0.014 Kcm/kV respectively in 0.98BZCT-0.02BZ ceramics. Thus, BZCT-BZ ceramics are appealing candidates for energy storage and electrocaloric application. [ABSTRACT FROM AUTHOR]

Smart ferroelectric lead zirconate titanate (PbZr0.52Ti0.48O3) was synthesized in the morphotropic phase boundary by a sol-gel autocombustion strategy. The as-prepared powder was calcined at three different temperatures, 700, 800, and 900 °C for 3 h, each. The tetragonality of the final product increases with the rise of calcination temperature. Thermal gravimetric analysis and differential thermal gravimetric analysis depicted that complete crystallization of PZT was observed at 400 °C. Structural, vibrational, and microstructure studies were investigated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy investigated for grains and elemental analyses and high-resolution transmission electron microscopy (HR-TEM). Results of XRD and HR-TEM were compatible, showing the formation of nanocrystalline powder with coexisting tetragonal and rhombohedral phases. Rietveld refinement of XRD data was carried out using material analysis using diffraction software in order to obtain the lattice constants. For mechanical and electrical measurements, disks were pressed at 10MPa. The samples were burned out at 500 °C for 1 h and then 1100 °C for 2 h to obtain more dense disks. The surfaces of the disks were coated with silver paste, followed by burning out for almost an hour. Dielectric and piezoelectric characteristics for the fabricated PZT samples were determined in detail. From these analytical techniques and collected data, one can deduce that the sample annealed at 900 °C can be used as an ultrasonic transducer in various metrological applications. [ABSTRACT FROM AUTHOR]

Lead-free ceramics based on bismuth sodium lanthanum titanate (Bi0.4871Na0.4871La0.0172TiO3: BNLT) and barium titanate (BaTiO3: BT) were prepared by a modified two-step mixed-oxide method. Effects of BT content on the phase transition, thermal expansion behavior, mechanical and electrical properties of lead-free BNLT-BT ceramics were studied. The Burn's temperature and local polarizations were estimated from the thermal expansion data. Various aspects of understanding the polarization behavior and other effects in this system have also been investigated and discussed. The 0.96BNLT-0.04BT ceramics have shown the d33 value of 135 pC/N. The coercive field (Ec) and remanent polarization (Pr) were found to be 24 kV/cm and 9.0 µC/cm2, respectively. This may be useful in the future development of multifunctional lead-free materials in electronic applications. [ABSTRACT FROM AUTHOR]

Due to the substitution of complex ions into B-sites is very interesting in recent, lead-free Bi0.47Na0.47Ba0.06Ti1−x(LiNb)xO3 (BNBT1−xLNx) ceramics (with x = 0–0.04) were fabricated by the solid-state combustion method. The influence of (LiNb)4+ (x) on the phase structure, microstructure, and electrical properties was investigated. The X-ray diffraction (XRD) patterns exhibited a pure perovskite structure for all specimens. Coexisting rhombohedral and tetragonal phases were observed in all samples and the tetragonal phase increased with increased x, as analyzed by the Rietveld refinement method. The morphology of the BNBT1−xLNx ceramics, obtained by scanning electron microscopy (SEM), revealed almost-round grain shapes and anisotropic grain growth. The density and average grain sizes decreased from 5.84 to 5.54 g/cm3 and 1.7 to 0.9 µm, respectively, when x increased from 0 to 0.04. The grain size distribution decreased with increased (LiNb)4+ content. A reduction in the dielectric properties was observed, due to the phase ratio changing away from a morphotropic phase boundary (MPB), an inferior microstructure, and low density caused by (LiNb)4+ substitution. The (LiNb)4+ substitution induced the transition from non-ergodic relaxor to ergodic relaxor ferroelectric state. [ABSTRACT FROM AUTHOR]

In this paper, Bi(1-x)LaxFeO3 ceramics were processed considering two compositions inside (Bi0.85La0.15FeO3) and outside (Bi0.95La0.05FeO3) the morphotropic phase boundary that separates the rhombohedral and orthorhombic phases. An unusual magnetic behavior, characterized by a double hysteresis loop, was observed at room temperature for the Bi0.85La0.15FeO3 sample. Langevin analyses revealed that this behavior is related to both the linear and non-linear components of the magnetization, indicating possible changes of the magnetic phase with doping. [ABSTRACT FROM AUTHOR]

The morphotropic phase boundary (MPB) region of the BFO-BTO solid solution is studied by comprehensive macroscopic and local methods, focusing on the synthesis conditions that influence the final phase composition and functional response. The difference between the phase distribution and local switching behavior in two sets of the BFO-BTO solid solutions prepared with different applied pressures is revealed and attributed to the local chemical inhomogeneity forming due to certain differences in the solid-state sintering reactions. More homogeneous mixing of the polar and non-polar phases stimulates the non-polar-to-polar phase transition and widening the MPB region. [ABSTRACT FROM AUTHOR]

Ferroelectric materials at morphotropic phase boundary (MPB) exhibit large piezoelectric coefficients and thus are widely used as piezoelectric actuators and sensors. Three different phase diagram topologies have been reported in various ferroelectric MPB systems: one with a cubic(C)-tetragonal(T)-orthorhombic(O)-rhombohedral(R) quadruple point; another with a C-T-R triple point and the other with a C-T-R along with a T-O-R triple point. However, it is unclear which phase diagram topology would give the best piezoelectric property. Here in this work, we obtain the above three different MPB phase diagram topologies by Landau free energy. It was found that among the three phase diagram topologies, the one with a T-O-R triple point exhibits superior piezoelectric property at the T-O-R triple point because of the small polarization anisotropy required by the simultaneous thermodynamic equilibrium of three ferroelectric phases. This work could guide the design of piezoelectric materials. [ABSTRACT FROM AUTHOR]

Ceramics of 0.94Bi0.5Na0.5TiO3-0.06BaTiO3 (0.94BNT-0.06BT) were synthesized by the solid-state combustion technique with various calcination and sintering temperatures (600-800 °C and 1100-1200 °C). A pure perovskite phase was obtained from the powder calcined at 750 °C for 2 h. The phase structure, microstructure, dielectric, ferroelectric and piezoelectric properties of the 0.94BNT-0.06BT ceramics were investigated. The XRD patterns showed coexisting phases of rhombohedral (R) and tetragonal (T) in all samples. Moreover, a good R:T phase ratio of 53:47, as found by Rietveld refinement, good grain growth and high density (5.84 g/cm3) were found with a sintering temperature of 1150 °C for 2 h. An excellent maximum dielectric constant (εm = 8405), good ferroelectric properties (Pr = 28.2 µC/cm2 and Ec = 22.1 kV/cm) and a high piezoelectric coefficient (161 pC/N) were observed in this sample, which was near a morphotropic phase boundary (MPB). [ABSTRACT FROM AUTHOR]

Using composition designing, Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) ceramics with compositions around the morphotropic phase boundary (MPB) were prepared by the solid-state reaction method via the columbite and wolframite precursor techniques. X-ray diffraction (XRD) measurement and XRD peaks fitting combined with electrical performance characterization confirm the occurrence of composition-induced ferroelectric phase change, and the sintered PIN-PMN-PT ceramics present the coexistence of rhombohedral and tetragonal ferroelectric phases. Composition exerts great influence on the relative density of the sintered ceramics, and the 0.28Pb(In1/2Nb1/2)O3-0.40Pb(Mg1/3Nb2/3)O3-0.32PbTiO3 (0.28PIN-0.40PMN-0.32PT) ceramics exhibit rather uniform microstructural morphology with high relative density of 94.4%. Dielectric, ferroelectric, and piezoelectric performance characterization also confirm the existence of the MPB effects, where the composition having performance maximum presents slight difference, proving that MPB has the composition region. Dielectric response behavior fitting and Raman spectroscopy measurement confirm the PIN-PMN-PT ceramics approach normal ferroelectrics with apparent diffusive transition characteristic and the occurrence of composition-induced ferroelectric phase change. [ABSTRACT FROM AUTHOR]

Density functional theory was used to inspect the structural properties and morphotropic phase boundaries (MPBs) of Ag1-xKxNbO3 (AKN) solid solutions. Structural properties of pristine AgNbO3 in Pbcm and Pmc21 phases were firstly investigated. The obtained crystal structures were found to be in good agreement with those from experiments. From the formation energy calculation of AKN solid solutions, the coexistences between Pbcm and Pmc21 phases and between Bmm2 and Pm phases were found to be in the composition ranges of x<"0.46" and x>"0.46," respectively. Therefore, the MPB separating the antiferroelectric and the ferroelectric phases can be specified at x ≈ "0.46." This theoretical study provides x ≈ "0.46" as a suggestive composition probably useful to acquire superior piezoelectricity for the utilization of AKN with reduced volatility of alkali elements at the A-site. [ABSTRACT FROM AUTHOR]