Properties Of Ferroelectric Ceramics Research Articles

Ferroelectric properties of rare-earth oxides doped (K 0.4Na 0.6) 0.95Li 0.05(Nb 0.95Sb 0.05)O 3 lead-free piezoceramics

The rare-earth oxides (Pr 2O 3 and Yb 2O 3)-doped (K 0.4Na 0.6) 0.95Li 0.05(Nb 0.95Sb 0.05)O 3 [KNNLS] ceramics were prepared using conventional solid sintering method for improving the ferroelectric properties of KNN-based ceramics. The effects of rare-earth oxides on the crystal structure, microstructure, dielectric and ferroelectric properties of the ceramics were systematically studied. The Curie temperature ( T c) decreases slightly with the increase of Pr 2O 3 and Yb 2O 3. The results show that Pr 2O 3 and Yb 2O 3 can greatly enhance the ferroelectric properties of KNNLS. The KNNLS-0.1 mol% Pr 2O 3 ceramic and KNNLS-0.1 mol% Yb 2O 3 ceramic show excellent ferroelectric properties: P r = 42.8 μC/cm 2, E c = 7.2 kV/cm and P r = 37.3 μC/cm 2, E c = 12.8 kV/cm, respectively.

Estimation of Intrinsic Contribution of Piezoelectric Properties in Ferroelectric Ceramics

A domain switching model is proposed to estimate the intrinsic contribution of piezoelectric properties in pseudocubic (rhombohedral) ferroelectric ceramics. Two-dimensional orientation distribution function (ODF) is used to describe domain patterns. The estimation of intrinsic contribution of piezoelectric properties is then achieved through tensor calculation and integration via the ODF. Our approach treats saturated and unsaturated domain texture in a unified scheme, while the inverse pole figure method reported in literature could not deal with unsaturated domain texture. The numerical method is useful in separation of intrinsic and extrinsic contribution of piezoelectric effect and in tailoring piezoelectric properties of ferroelectric ceramics.

Ferroelectric Properties of Pb(Zr<sub>1/2</sub>Ti<sub>1/2</sub>)O<sub>3</sub>-Pb(Zn<sub>1/3</sub>Nb<sub>2/3</sub>)O<sub>3</sub> Ceramics under Compressive Stress Applied Perpendicular to Electric Field

Effects of perpendicular compressive stress on the ferroelectric properties of ceramics in PZT-PZN system were investigated. The (1-x)Pb(Zr1/2Ti1/2)O3-xPb(Zn1/3Nb2/3)O3 or (1-x)PZT- (x)PZN (x = 0.1-0.5) ceramics were prepared by a conventional mixed-oxide method. The ferroelectric properties were measured under compressive stress applied perpendicular to an electric field direction at stress levels up to 90 MPa using a compressometer in conjunction with a modified Sawyer-Tower circuit. It was found that with increasing compressive stress the area of the ferroelectric hysteresis (P-E) loops, the maximum polarization (Pmax), and the remanent polarization (Pr) decreased, while the coercive field (Ec) remained relatively constant. These results were interpreted through the domain switching, clamping of domain walls and de-poling mechanisms.

Changes in ferroelectric properties of ceramics in lead magnesium niobate–lead titanate system with compressive stress

Effects of compressive stress on the ferroelectric properties of Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN-PT) ceramics were investigated. The ceramics with the formula (1−x)Pb(Mg1/3Nb2/3)O3−(x)PbTiO3 or (1−x)PMN−(x)PT (x=0.1–0.5) were prepared by a conventional mixed-oxide method. Dense perovskite-phase PMN-PT ceramics with a uniform microstructure were obtained. The ferroelectric properties were measured under compressive stress (0–75 MPa) using a homebuilt compressometer in conjunction with a modified Sawyer–Tower circuit. The experimental results revealed that the superimposed compression stress significantly reduced both the dissipation energy and the polarizations of the near morphotropic phase boundary compositions, i.e., 0.8PMN-0.2PT, 0.7PMN-0.3PT, and 0.6PMN-0.4PT, while the stress influence was much less in other compositions. On the contrary, the applied compressive stress showed little or no influence on the coercive field. These results were interpreted through the non-180° ferroelastic domain switching processes and the stress induced decrease in the switchable part of domains.

Investigating the effect of oxygen vacancy on the dielectric and electromechanical properties in ferroelectric ceramics

The effect of oxygen vacancy on the dielectric and electromechanical properties in lead titanate zirconate based ferroelectric ceramics is discussed in this paper. The presence of oxygen vacancy forms a defect-dipole inside a perovskite cell. This defect-dipole contributes to the unswitchable polarization and influences the alignment of the ferroelectric dipole in the same cell as well. The latter is due to the displacement of the B-site cation, which contributes to the switchable polarization. It is found that a double hysteresis emerges when the alignment of defect-dipole conforms with the crystal orientation, which is perpendicular to the measured polarization. Moreover, the optimal electromechanical property can be obtained by careful adjustment of c-domain volume fraction and the alignment of defect dipoles. Monte Carlo simulation based on the four-state Potts model is presented. Calculation results are compared with experiments.

Anomalies of the pyroelectric and dielectric properties of ferroelectric ceramics of the PbZr1-x Ti x O3 system with 0.06 ≤ x ≤ 0.35 at the R3c↔R3m phase transition

The temperature dependences of the pyroelectric and dielectric properties of ferroelectric ceramics of the PbZr1 − x Ti x O3 binary system with x = 0.06, 0.07, 0.08, 0.1, 0.15, 0.2, 0.25, 0.3, and 0.35 have been obtained synchronously for each sample in the range of the structural phase transition between the states with the symmetry space groups R3c ↔ R3m. It is established that the temperatures of this phase transition for unpolarized and polarized samples coincide in the range 0.06 ≤ x ≤ 0.15. In this case, the x−T phase diagram, constructed on the basis of the pyroelectric and dielectric data, is in excellent agreement with the X-ray diffraction data on single crystals in this concentration range. The effect of dc electric fields from 5 × 105 V m−1 did not lead to any temperature shifts of the R3c ↔ R3m phase transition for the compositions with 0.06 ≤ x ≤ 0.25.

Ferroelectric properties of Pb(Zr1/2Ti1/2)O3–Pb(Zn1/3Nb2/3)O3 ceramics under compressive stress

Effects of compressive stress on the ferroelectric properties of ceramics in PZT–PZN system were investigated. The ceramics with a formula (1− x )Pb(Zr 1/2 Ti 1/2 )O 3 – x Pb(Zn 1/3 Nb 2/3 )O 3 or (1− x )PZT–( x )PZN ( x = 0.1–0.5) were prepared by a conventional mixed-oxide method. The ferroelectric properties under the compressive stress of the PZT–PZN ceramics were observed at the stress levels up to 170 MPa using a compressometer in conjunction with a modified Sawyer–Tower circuit. It was found that with increasing compressive stress the area of the ferroelectric hysteresis ( P – E ) loops, the saturation polarization ( P sat ), the remnant polarization ( P r ), and the coercive field ( E c ) decreased. These results were interpreted through the non-180° ferroelastic domain switching processes.

Stress-dependent ferroelectric properties of Pb(Zr1/2Ti1/2)O3–Pb(Zn1/3Nb2/3)O3 ceramic systems

Abstract Effects of compressive stress on the ferroelectric properties of ceramics in PZT–PZN systems were investigated. (1 − x )Pb(Zr 1/2 Ti 1/2 )O 3 ( x Pb(Zn 1/3 Nb 2/3 )O 3 or (1 − x )PZT–( x )PZN ( x = 0.1–0.5) ceramics were prepared by a conventional mixed-oxide method. The ferroelectric properties under compressive stress of the PZT–PZN ceramics were observed at stress levels up to 170 MPa using a compressometer in conjunction with a modified Sawyer–Tower circuit. It was found that with increasing compressive stress the area of the ferroelectric hysteresis (P–E) loops, the saturation polarization ( P sat ), the remanent polarization ( P r ), and the coercive field ( E c ) decreased. These results were interpreted through the non-180° ferroelectric domain switching processes.

Synthesis and Dielectric and Ferroelectric Properties of Ceramics in (1-x)Pb(Zr1/2Ti1/2)O3–(x)Pb(Co1/3Nb2/3)O3 System

Ceramics in a PZT–PCN system with the formula (1-x)Pb(Zr1/2Ti1/2)O3–(x)Pb(Co1/3Nb2/3)O3, where x = 0.1–0.5, were prepared using a solid-state mixed-oxide technique (the columbite-wolframite precursor method). The phase formation behavior and microstructure were studied using X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM), respectively. The dielectric and ferroelectric properties of the compounds were studied and discussed. Phase-pure perovskites of PZT–PCN ceramics were obtained over a wide compositional range. In addition, the XRD, dielectric, and ferroelectric properties confirmed that the morphotropic phase boundary (MPB) composition between the tetragonal and pseudo cubic phases of this system lied between 0.2 ≤x ≤0.3.

MODEL FOR GRAIN SIZE EFFECT ON DIELECTRIC NONLINEARITY OF FERROELECTRICS

ABSTRACT Dielectric nonlinearity is an important characteristic of ferroelectrics. It is assumed that in ferroelectrics the grains are all uniform, in order and cubic-shaped. Moreover, the dielectric constant of the grain boundary does not vary with direct current bias. And then the grains and the grain boundaries were modeled in terms of capacitors and resistors. Based on these analyses, a model for grain size effect on dielectric nonlinearity of ferroelectrics was established. In this model there are some parameters such as the grain size and the grain boundary width, which intensively influence on the dielectric properties of ferroelectric ceramics and thin films. The accuracy of the model prediction was quantitatively verified by our experimental data. The results proved that the above model can describe the grain size effect on dielectric nonlinearity of ferroelectrics.

Controlling the physical properties of PbIn0.5Nb0.5O3 ferroelectric ceramics by intense mechanical action with shear

PbIn0.5Nb0.5O3 (PIN) ferroelectric relaxer ceramics obtained by the solid-phase method is studied. Prior to sintering, the synthesized charge is subjected to mechanical action in Bridgman anvils at room temperature. The electrophysical properties of the reference sample and test samples are compared. It is concluded that mechanical treatment of the material at the stage of preparation allows one to control the physical properties of ferroelectric ceramics. Starting from a certain amount of the action, the electrophysical properties of PIN ceramics vary nonmonotonically.

Dielectric and ferroelectric properties of lead zirconate titanate-barium titanate ceramics prepared by a modified mixed-oxide method

Ceramic solid solutions within the system (1 − x)Pb(Zr 0.52Ti 0.48)O 3– xBaTiO 3, where x ranged from 0.0 to 1.0, were prepared by a modified mixed-oxide method. The crystal structure, microstructure, dielectric and ferroelectric properties of the ceramics were investigated as a function of composition via X-ray diffraction (XRD), scanning electron microscopy (SEM), dielectric spectroscopy and hysteresis measurement. The (1 − x)PZT– xBT solid solutions showed that with increasing solute concentration (BT or PZT), the phase transformation became diffuse. This was primarily evidenced by an increased broadness in the dielectric peak, with a maximum peak width occurring at x = 0.5. The P– E hysteresis loop measurements showed that while BT showed a well-formed hysteresis loop, PZT and 0.1PZT–0.9BT ceramics exhibited pinched-shape hysteresis loops due to abnormal domain switching mechanism. In addition, other compositions exhibited very slim-loop hysteresis occurred in materials with mixed phase or with diffuse phase transition. This observation was believed to be caused by nano-scaled chemical heterogeneity in these compositions.

Uniaxial stress dependence of ferroelectric properties of xPMN-(1–x)PZT ceramic systems

Effects of uniaxial compressive pre-stress on the ferroelectric properties of ceramics in the PMN-PZT system are investigated. The ceramics with a formula xPb(Mg1/3Nb2/3)O3-(1-x)Pb(Zr0.52Ti0.48)O3 or xPMN-(1-x)PZT when x=0.0, 0.1, 0.3, 0.5, 0.7, 0.9, and 1.0 are prepared by a conventional mixed-oxide method. The ferroelectric properties under the uniaxial compressive pre-stress of the PMN-PZT ceramics are observed at the stress levels up to 13 MPa using a compressometer in conjunction with a modified Sawyer–Tower circuit. It is found that with increasing compressive pre-stress levels the area of the ferroelectric hysteresis (P–E) loops, the saturation polarization (Psat), the remanent polarization (Pr), and the coercive field (Ec) decrease. These results are interpreted through the non-180° ferroelastic domain-switching processes. Finally, the calculated differential permittivity for all the xPMN-(1-x)PZT ceramics, except for 0.5 PMN-0.5 PZT, decreases with increasing applied stress.

Dielectric Properties of Spark Plasma Sintered (SPS) Barium Strontium Titanate (BST) Ceramics

Grain size can have a very important effect on the dielectric properties of ferroelectric ceramics through the interaction of domain structures and grain boundaries. In this work, Ba0.6Sr0.4TiO3 ceramics were fabricated to controlled grain sizes using a spark plasma sintering (SPS) technique which can produce dense ceramics at greatly reduced sintering temperatures and times. The microstructure and dielectric properties of SPS produced ceramics have been characterised and compared with those from conventional presureless sintered ceramics. The results show that SPS ceramics exhibit a duplex microstructure with 1-3 μ m BST grains surrounded by submicron BT and ST grains. Consequently, they show a significantly diffused transition in permittivity and reduced dielectric losses in the ferroelectric region compared to conventionally sintered ceramics. This is believed to result largely from the large differences in grain sizes and domain structures. The mechanisms will be discussed in terms of domain walls contributions.

Impact of Structure Ordering and Defects on Properties of Complex Ferroelectric Perovskites

Influence of the structure ordering, modification and defects on the properties in ferroelectric ceramics and thin films are investigated. Structural changes in perovskite type compounds with general formula (1−x)Pb(B3+,Nb)TiO3−xPbTiO3 are realized by variation of it composition (by exchange of ions B3+ in B sublattice). The crystallographic features of Pb(Lu1/2Nb1/2)O3—PbTiO3 (PLuNT) and PbSc1/2Nb1/2O3-PbLu1/2Nb1/2O3 (PSN-PLuN) compounds are discussed with respect to dielectric, polarization and electro-mechanical properties. The heterovalent substitution of Pb2+ by La3+ in PLuNT ceramics either in both components and maintaining the PbTiO3 unmodified shifts the MPB to the pseudomonoclinic side of phase diagram. The initial unmodified material “softens”—coercive field Ec decreases and simultaneously high values of maximum and remnant polarization are characteristic.Antiferroelectric thin films display higher radiation resistance than ferroelectric heterostructures up to a neutron fluence of 2*1022 m−2 (E > 0.1 MeV). The strong dependence of radiation-induced change of properties from the quality of the films (epitaxial versus polycrystalline) was found.

Morphology of PZT-PMN Films Grown from Airflow

Lead zirconate titanate-lead magnesium niobate (PZT-PMN) films with thicknesses in the range 5 to 200 μm were fabricated by deposition from airflow at room temperature. Precursor powders of PZT and PMN were mixed in a ball mill and entrained in an airflow generated by a commercial jet-mill (Micron-Master 02-506). Films were grown at a rate of 1 μm/minute onto the Ni and tungsten carbide substrates exposed to the air-powder mixture. Unfired, poled PZT-PMN films provided an audio acoustic response and form translucent 20–30 μm thick layers. Full density of the air-flow deposited materials has been achieved at temperatures 450°C lower than that typical for ball milled bulk PZT-PMN ceramics. After sintering for 2 hours at 850°C PZT-PMN ceramics with relative density of 99.5%, ϵ ∼ 2170, tan δ ∼ 0.009 @1 kHz and acceptable piezoelectric properties was obtained. Films sintered 2 hours at 1000°C showed remnant polarization P r = 26 μC/cm2, P s = 36 μC/cm2 @95 kV/cm, and 50 Hz ac electric breakdown field as high as 120–170 kV/cm. Unusual grain morphology governs improved sinterability and enhanced properties of ferroelectric ceramics. Optical and AFM micrographs revealed needle-like grains preferentially oriented parallel to the air-powder stream. As-deposited films were found to be very non-uniform across the thickness: glass-like and with tensile strain on the contact surface. This strain is released and film microcrystalline structure becomes uniform in annealed film.

Microscopic Studies of the Crystalline Structure of Ferroelectric and High Temperature Superconductor Layers

Properties of ferroelectric ceramics and superconductors essentially depend on the microstructure formed during thermal processing of the material. Active electronic materials synthesized from oxides and carbonates by solid state reaction, and ceramic samples produced by conventional technology were studied. Thick layers have been sedimented on ceramics and single crystal substrates and fired in accordance with melt textured growth (MTG) technology. Choice of the substrate--its lattice parameters and structure--is essential. The surface morphology and structure of high temperature superconductor layers prepared on passive substrates of different crystal structures were studied by scanning electron microscopy. The effect of substrate material on the structure formation of the layers is discussed.

Effect of synthesis temperature on the ferroelectric properties of ceramics based on lead zirconate titanate and alkali niobates

Ferroelectric piezoceramics based on lead zirconate titanate (PZT) and alkali niobates were prepared by solid-state reactions followed by hot pressing, and their properties were studied. The results demonstrate that the ceramics can be divided into two groups, according to the effect of synthesis temperature on their electrical properties. In one group (ceramics based on PZT and sodium potassium niobate), the range of optimal synthesis temperatures is as broad as ≃200°C, and the properties vary insignificantly across this range. In the other group (ceramics based on lithium niobate and sodium lithium niobate), the properties show sharp extrema within a narrow range of synthesis temperatures (≃20°C). These findings are interpreted in terms of the cation composition of the materials. The obtained data can be used to optimize conditions for the preparation of various ferroelectric piezoceramics.

Grain-Boundary Effect on the Curie-Weiss Law of Ferroelectric Ceramics and Polycrystalline Thin Films: Calculation by the Method of Effective Medium

The influence of grain boundaries on the dielectric properties of ferroelectric ceramics and polycrystalline thin films is described theoretically by the method of effective medium. Grain boundaries are modeled by low-permittivity (“dead”) layers, which do not exhibit ferroelectric instability. The effective permittivity of a polycrystalline material is calculated in the paraelectric regime above the transition temperature. The calculations are based on the solution of electrostatic problem for a spherical dielectric inclusion separated from the surrounding dissimilar matrix by a low-permittivity interface layer. For isotropic bulk ceramics, an analytic expression is derived for the effective permittivity as a function of the grain size, dead-layer thickness, and its permittivity. Temperature dependence of the aggregate dielectric response is calculated for BaTiO3 (BT) ceramics of different grain sizes and found to be in good agreement with measurements. It is shown that grain boundaries not only renormalize the Curie-Weiss temperature and constant, but may also cause deviations from the Curie-Weiss law. For BT polycrystalline thin films grown on dissimilar substrates, numerical calculations of the effective dielectric constants are performed, taking into account both the grain-boundary and substrate effects on the film anisotropic dielectric response. Theoretical predictions are compared with the grain size dependence of the permittivity of BT films grown on Pt-coated Si.

Engineering of piezoelectric properties in ferroelectric ceramics and thin films

The paper discusses different possibilities for controlling piezoelectric properties of ferroelectric materials and devices. The piezoelectric properties engineering can be made on different scales. Tuning of the piezoelectric response by controlling contributions from domain walls displacement is used to illustrate engineering on nanometer scale. Texture control in ferroelectric films and grain size control is discussed as an example of property control on micrometer scale. Finally, engineering on macroscopic (millimeter) scale is illustrated by amplification methods employed in multilayer actuators and different bimorph-type structures as well as by control of electro-mechanical properties in polymer-ceramic composites.