Properties Of Ferroelectric Ceramics Research Articles

Frequency-dependent ferroelectric and electrocaloric properties in barium titanate-based ceramics based on Maxwell relations

In this work, the frequency dependence of ferroelectric and electrocaloric properties in barium titanate-based ceramics was studied based on Maxwell relations. It is found that the maximum and remnant polarization will decrease while the coercive field increases a lot with rising frequency from 0.1 to 10[Formula: see text]Hz, indicating that polarization rotation and domain switching become difficult at high frequencies. The electrocaloric properties show the different frequency dependence at different phase structures. Isothermal entropy change ([Formula: see text]) and adiabatic temperature change ([Formula: see text]) are similar around/above Curie temperature ([Formula: see text], showing tiny frequency dependence. However, [Formula: see text] and [Formula: see text] display the obvious frequency dependence below [Formula: see text], especially in the orthorhombic–tetragonal phase-transition region with a stable ferroelectric phase, and this frequency dependence becomes more obvious under a low-electric field. It is also found that increasing the frequency can weaken the electric field dependence of electrocaloric strength. This work gives a general profile of frequency dependence for electrocaloric properties in ferroelectric ceramics.

Correlation between sintering temperature and dwell time on structural and ferroelectric properties of NiTiO3-CoFe2O4 ceramics

The 0.9NiTiO3-0.1CoFe2O4 ceramic was prepared by sol-gel method. The structural and ferroelectric properties of the ceramic were investigated. Structure of the materials was analyzed by X-ray diffraction and scanning electron microscopy. Fabricated materials consists of NiTiO3 with rhombohedral phase structure and CoFe2O4 with cubic structure. The effect of sintering temperature and dwell time on the phase, microsctructure and ferroelectric properties of the ceramics was investigated. As the sintering temperature and dwell time increased, the density of the bulk sample was improved. The material sample was sintered at 1200oC for 10 h with large particle size (~6 µm), few pores and high density ~97.5%. The composite material displayed ferroelectric properties, as evidence from the characteristic hysteresis loop observed in ferroelectric materials. At sintering temperatures of 1000°C and 1100°C for 2 and 5 h, the sample exhibited poor ferroelectric characteristics. However, when the sample was sintered at 1200°C for 10 h, a notable enhancement in ferroelectric properties was observed.

Polarization extension yielding ultrahigh piezoelectric response in xPb(Nb2/3Ni1/3)O3-(1-x)Pb(Zr0.3Ti0.7)O3 ferroelectrics ceramics

The heightened piezoelectric performance observed in most explored perovskite systems is typically attributed to the electric-field-induced phase transition near the morphotropic phase boundary (MPB) or polymorphic phase boundary (PPB). This study, however, unveils a distinct piezoelectric enhancement mechanism in the xPb(Nb2/3Ni1/3)O3-(1–x)Pb(Zr0.3Ti0.7)O3 (PNN-PZT) system, diverging from the MPB/PPB-centered piezoelectric systems. Notably, the composition with x = 0.55, positioned close to the tetragonal-pseudocubic (T-PC) phase boundary, achieves an unprecedented piezoelectric coefficient (d33) of 1264 pC/N, while retaining a tetragonal local structure. Importantly, on a local scale, electric fields do not incite phase transitions, suggesting that the exceptional piezoelectric performance in PNN-PZT stems from polarization extension near the T-PC boundary. Distinct from other mechanisms, the relative permittivity significantly increases post-poling due to this particular enhancement process. The dielectric behavior in poled specimens does not exhibit a conspicuous change at the ferroelectric-relaxor transition temperature. However, both the relative permittivity and planar electromechanical coupling coefficient experience a sharp rise in the temperature range of −25 °C to 25 °C. This investigation underscores the pivotal role of designing compositionally-driven T-PC phase boundaries, presenting a promising avenue for enhancing piezoelectric properties in ferroelectric ceramics.

Structural and compositional indicators of ferroelectric properties of KNN ceramics

Improvement of the properties of KNN ceramics requires tools allowing one to reveal a relation between the structure and composition, on the one hand, and ferroelectric property, on the other. In this work, lead-free (1-x) (K0.5Na0.5)NbO3-xAgNO3 and (1-x) (K0.5Na0.5)NbO3-xBaZrO3 ceramics with different contents of the ferroelectric phase have been studied using piezoresponse force microscopy (PFM), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). A correlation between the PFM image contrast, the SEM phase contrast (BEI) and the elemental composition of the phases (EDS) has been found. Specimens with a low content of the ferroelectric phase contain secondary phase with composition and structure different from those of ABO3 perovskite. XPS has shown the presence of two types of potassium ions with different chemical states, i.e., inside (K1) and outside (K2) the perovskite lattice. The observed correlation between the ferroelectric properties of the ceramics and the K2 concentration allows one to use it as a reliable indicator of ferroelectric properties.

Domain Engineering in Bulk Ferroelectric Ceramics via Mesoscopic Chemical Inhomogeneity.

Domain engineering in ferroelectrics endows flexibility for different functional applications. Whereas the domain engineering strategy for single crystals and thin films is diverse, there is only a limited number of strategies for bulk ceramics. Here, a domain engineering strategy for achieving a compact domain architecture with increased domain‐wall density in (K,Na)NbO3 (KNN)‐based ferroelectric ceramics via mesoscopic chemical inhomogeneity (MCI) is developed. The MCI‐induced interfaces can effectively hinder domain continuity and modify the domain configuration. Besides, the MCI effect also results in diffused phase transitions, which is beneficial for achieving enhanced thermal stability. Modulation of chemical inhomogeneity demonstrates great potential for engineering desirable domain configuration and properties in ferroelectric ceramics. Additionally, the MCI can be easily controlled by regulating the processing condition during solid‐state synthesis, which is advantageous to industrial production.

Novel non-stoichiometric (Ba0.91Ca0.09)x(Zr0.18Ti0.82)O3 ferroelectric ceramics with improved diffuse phase transition and dielectric tunable performance

Dielectric tunable properties in ferroelectric ceramics have been optimized by a variety of approaches, e.g., isovalent/aliovalent substitution, system composite et al., while the study of non-stoichiometric regulation on the performance of BCZT ceramics was rarely concerned. Herein, a series of novel non-stoichiometric (Ba0·91Ca0.09)x (Zr0·18Ti0.82)O3 (BCZTx) ceramic specimens were successfully prepared via solid-state reaction. The microstructures of BCZTx ceramics are simultaneously investigated through XRD and SEM. The diffuse phase transition (DPT) behaviour of BCZTx ceramics are studied by the Lorentz-type empirical formula. The significant enhancement of DPT behaviour is observed at x = 1.03, which probably due to the coaction of the generation of partial Schottky defects and prominent reduction of grain size. Furthermore, a high tunability (k) 87.80%, low dielectric loss (tan δ) 0.141%, and a remarkably enhanced FOM of 623 are achieved in x = 0.99 at a low DC bias electric fields (BEFs) of 7.28 kV/cm and room temperature (RT), which is superior to that of the stoichiometric BCZT ceramics and other available reported BT-based ceramics systems in term of the dielectric tunable properties. Meanwhile, it shows that the temperature dependent CQF value of x = 0.99 remained advantageous around the RT. These findings suggested that non-stoichiometric BCZTx ceramics with x = 0.99 are significantly competitive in the applications of dielectric tunable devices at RT. The non-stoichiometric regulation is an effective approach in improving the dielectric tunability properties of BCZT ceramics.

Effects of density inhomogeneity in green body on the structure and properties of ferroelectric ceramics

Effects of density inhomogeneity in green body on the structure and properties of ferroelectric ceramics

Loading rate independence of the evolutions of remnant state variables and linear material properties in ferroelectric ceramics during ferroelastic switching

Two series of compressive stress cycles are applied to a commercial poled ferroelectric cube specimen at room temperature $$\,20\,{^\circ }{\text{C}}$$ : one is big stress cycles of increasing magnitude and the other small stress cycles of constant magnitude. The former is applied at five different rates to induce domain switching, and the latter at the fastest loading rate possible to estimate the evolutions of linear material properties during switching. From measured data, we find that the relationships among remnant polarization, longitudinal remnant strain, and transverse remnant strain are equal and the same independent of loading rates. The dependence of piezoelectric coefficient, elastic compliance coefficients, and Poisson’s ratio on remnant state variables is also the same independent of loading rate. These observations lead to conclude that switching processes by compressive stress are loading rate independent, which would be useful in developing constitutive equations for nonlinear behavior of ferroelectric ceramics.

Electrocaloric effect and dielectric properties in ferroelectric ceramics based on solid solution of barium-calcium titanate

Barium titanate based ceramics is the most common class of lead-free ceramics due to its high values of dielectric constant, polarization, piezo- and electrocaloric effects. In this paper dielectric properties and electrocaloric effect in ceramics based on solid solution of barium-calcium titanate had been studied. It was shown, that increasing of calcium titanate in solid solution leads to increasing of dielectric constant and electrocaloric effect, simultaneouslyit leads to decreasing of leakage currents. While increasing fraction of calcium titanate from 0% to 10%, dielectric constant at frequency of 1 kHz rises from 10500 to 13600, maximum adiabatic electrocaloric response at ΔE = 1.3 V/μm rises from 0.5 K to 0.7 K.

Effect of Nb, Ta and Sb Addition on Structure and Electrical Properties of PZT Ceramics

Abstract In this study, the effect of Nb, Ta and Sb addition on the structure, dielectric and ferroelectric properties of the Pb(Zr0.5Ti0.5)O3 ceramics in the morphotropic phase boundary (MPB) region were investigated. Powders of pure PZT, PZT + 0.1 mol% Nb, PZT + 0.1mol% Ta and PZT + 0.1mol% Sb were synthesized by conventional mixed oxide method via a vibro-milling technique. All compositions of powders were uniaxially pressed in pellets and sintered at the temperature of 1275°C for 2h. Phase formation, dielectric and ferroelectric properties of ceramics were characterized by XRD, LCR meter and modified Sawyer–Tower Circuit respectively.

The dielectric, piezoelectric and ferroelectric properties of LaAlO3-doped Bi0.5Na0.5TiO3-BaTiO3 lead-free piezoceramics

ABSTRACTLaAlO3-doped Bi0.5Na0.5TiO3-BaTiO3(BNT-BT) lead-free piezoelectric ceramics with compositions near the rhombohedral–tetragonal morphotropic phase boundary (MPB) were prepared and investigated. The introduction of LaAlO3, which makes the ceramics samples avoid being fused, has a relatively large influence on the dielectric, piezoelectric and ferroelectric properties of BNT-BT ceramics. With the increase of doping concentration, these properties get weaker. But when the doping concentration of LaAlO3 is 0.2 mol%, the remnant polarization (Pr) and coercive field (Ec) are better than those in pure 0.93BNT-0.07BT ceramics. The ferroelectric properties of this ceramics appear an eccentric enhancement and the domain switch becomes more easily.

Влияние размера кристаллитов на электрокалорические характеристики в сегнетоэлектрических керамиках

Влияние размера кристаллитов на электрокалорические характеристики в сегнетоэлектрических керамиках

Ferroelectric ceramics manufactured from nano-sized powders of bi-containing layer-structured phases

ABSTRACTMethods to improve dielectric and piezoelectric properties of ferroelectric ceramics with high Curie temperatures (TC > 700 K) are discussed. In the first method improving the electrophysical properties is achieved due to a change in technology of the synthesis of powders of ferroelectric phases, and a proposed technological mode enables one to keep a composition of these powders due to a decrease of temperature of the synthesis of the chemically active powders and to a decrease of temperature of sintering. In this method high-temperature ferroelectric ceramics based on the Aurivillius phases are characterised by the piezoelectric coefficient d33 ≤ 40 pС / N and dielectric permittivity ϵT33/ϵ0≤ 230. The second method is concerned with ferroelectric phases of PbTiO3 – PbZrO3 – Bi4Ti3О12 – МеТiO3 (Ме = Са, Sr, Ва), and on this basis ceramics are formed with larger piezoelectric parameters and TC > 700 K. Temperature of the synthesis of powders based on ferroelectric phases, obtained using the low-temperature method, is lower by 430 K on the average, at reducing the process time range by more than 3 times.

Effect of Sintering Parameter on Ferroelectric Properties in PZT Based Ceramics

This research was conducted to improve the ferroelectric properties of PZT based ceramics by studying the effect of sintering conditions in terms of temperature and soaking time (time of sintering) on the ferroelectric properties of ceramics in the 0.8Pb (Zr1/2Ti1/2)O3-0.2Pb (Zn1/3Nb2/3)O3 system prepared by vibro-milling mixed-oxide method. The XRD patterns of specimens showed perovskite structure for all compositions. The pyrochlore phase was not observed in this system. The sintering temperature and soaking time affects the ferroelectric properties of ceramics by the optimum sintering condition for 0.8PZT-0.2PZN ceramic is sintered at 1250°C for 2h.

An approach to further improve piezoelectric and ferroelectric properties of (K0.5Na0.5)NbO3 ceramic

In this communication, an approach to further improve the electrical properties of (K0.5Na0.5)NbO3 (KNN) ceramic (abbreviated as KNN2) was reported. For the conventional ceramic technique (abbreviated as KNN1), the raw materials of K2CO3, Na2CO3 and Nb2O5 were directly used without further processing, while those for KNN2 were ball milled before mixing. The powders prepared by KNN2 exhibited smaller and uniform. The ceramics have higher densities than that of KNN1, which significantly improved the piezoelectric and ferroelectric properties of ceramics. The KNN2 ceramics exhibited very good piezoelectric properties with d33 = 123 pC/N, kp = 33.8 %, Qm = 219.8 and Pr = 20.2 μC/cm3, indicating that KNN2 is a strategy to obtain a dense KNN ceramic with more excellent electrical properties.

The Preparation and Properties of (Na<sub>0.5+x</sub>K<sub>0.5-2x</sub>Li<sub>x</sub>)NbO<sub>3</sub> Lead-Free Piezoelectric Ceramics

In this paper, the KNN powders with Li+ substituted (K0.5Na0.5)+ were prepared by the sol-gel method in order to make powders pure, (Na0.50+xK0.50-2xLix) -NbO3 (x=0, 0.04, 0.06, 0.08) ceramics were prepared by pressureless sintering. The phase composition of powders was determined by XRD. The effects of the Li+ substitution on piezoelectric and ferroelectric properties of ceramics were systematically studied for determining optimal Li+ content. Li+ can significantly increase the piezoelectric constant of ceramic. When Li+ content was 0.04, piezoelectric properties of ceramics were the best, d33=115 pC/N, Pr=6.35 μC/cm2, Ec=14.24 kV/cm.

Evolution of remnant state variables and linear material properties in ferroelectric ceramics during compressive loading and unloading

Abstract A pre-poled lead titanate zirconate (PZT) cube specimen was subjected to impulsive compression stress with increasing amplitude. Linear material properties were evaluated graphically from the measured responses. The material properties were plotted versus relative remnant polarization and fitted by quadratic curves. Then the specimen was subjected to compressive creep loading and unloading of various constant magnitudes. The linear material properties obtained from impulsive stress loading were used to calculate the evolutions of remnant state variables and material properties during the compressive creep loading and unloading. The magnitudes of polarization and strains that were induced and recovered during the creep loading and unloading were plotted and discussed.

Effect of La2O3 Addition on Electrical Properties of PZN-PZT Based Ceramics

In this study, compositions in the 0.2Pb(Zn1/3Nb2/3)O3-0.8Pb(Zr1/2Ti1/2)O3 based systems will be developed based on the material engineering approach (processing vs. electrical properties). This work involves the fabrication of high purity PZN-PZT based in ceramic forms, and a study of La2O3 addition on phase formation, microstructures and electrical properties was investigated which are especially important from the viewpoint of the development of practical piezoelectric materials. The effect of La2O3 addition was characterized on microstructure and electrical properties of PZN-PZT. Amounts of 0.05–1 wt% La2O3 were doped on 0.2PZN-0.8PZT. All compositions of powders were uniaxially pressed in pellets and sintered at the temperature 1250°C with dwell time 2 h. Phase and microstructure development, dielectric and ferroelectric properties of ceramics were characterized by XRD, SEM, LCR meter and Modified Sawyer–Tower Circuit respectively. In addition, the values of permittivity maximum and the temperature of permittivity maximum were substantially decreased by La-doping and these results show increased Pr, Ps and strain level but decreased Ec.

Effect of pulsed laser radiation on the structure and electrical properties of ferroelectric ceramics

Ceramic samples of barium titanate and solid solution of barium-strontium titanate subjected to pulsed laser irradiation have been studied by impedance spectroscopy. The measurements have been carried out in the frequency range 102–106 Hz and at temperatures in the range from 20 to 450°C. The experimental data are represented by the dispersion of the electric modulus. The activation energy of relaxation processes in the paraelectric phase has been calculated. Scanning electron microscopy has been used to obtain micrographs of the sample surfaces and the data on the elemental composition.

Piezoelectric activity of (1-x)[0.35Bi(Mg1/2Ti1/2)O3-0.3BiFeO3-0.35BiScO3] - xPbTiO3 ceramics as a function of temperature

The piezoelectric and ferroelectric properties of ceramics in the (1-x)[0.35Bi(Mg1/2Ti1/2)O3-0.3BiFeO3-0.35BiScO3] - xPbTiO3 (0.46 ≤ x ≤ 0.50) solid solution have been studied as a function of temperature with a view to establishing their potential for commercial usage as high TC actuators and sensors. The polarisation, unipolar and bipolar strain, piezoelectric coefficient d33 and coupling factor kp all increased with temperature consistent with softening of extrinsic and intrinsic contributions to piezoactivity as TC is approached. Small signal d33 and kp increased from 328 pm/V and ~0.45 at room temperature to >1100 pm/V and ~0.5, respectively, until depoling occurred at ~400°C, illustrating a significant improvement in operating temperature over PZT (~200°C) and demonstrating great potential for high temperature sensor applications. Bipolar (bi) and unipolar (uni) measurements (large signal, d* 33) normally used to demonstrate potential for actuation, revealed extremely promising values, d* 33(bi) = 940 pm/V and d* 33(uni) = 600 pm/V, up to 180°C, the limit of the experimental apparatus.