Polarization-electric Field Hysteresis Loops Research Articles

Enhanced ferroelectric order in Pb(Mg1/3Nb2/3)0.9Ti0.1O3 ceramics by ZnO modification

In this research, the effects of ZnO modification on ferroelectric order of Pb (Mg1/3Nb2/3)0.9Ti0.1O3 (PMNT) ceramics were studied through characterizations of dielectric and ferroelectric properties. The PMNT/xZnO (where x = 0, 0.4, 2.0, 4.0 and 11.0 mol.%) ceramics were prepared by solid state reaction and sintering process. The lattice parameter a and unit cell volume of pure PMNT ceramic were increased with ZnO modification. The temperature of maximum dielectric constant (Tmax), the freezing temperature (Tf), the depolarization temperature (Td) and the polar ordering temperature (TP) increased while the diffuseness parameter (δ) decreased with the increase in ZnO content, indicating an enhancement of ferroelectric ordering and a decrease in a degree of relaxor behavior of PMNT ceramics by ZnO modification. Polarization-electric field hysteresis loop and butterfly-like strain-electric field curve were displayed around room temperature in the 11.0 mol.% ZnO-modified PMNT sample, which indicated an establishment of polar macro domains. Electrostrictive coefficient (M) reached a highest value of 22.22 × 10−16 m2/V2 for the PMNT/4.0 mol.%ZnO ceramic, which made it a promising material for applications as electrostrictive actuators.

Preparation and Ferroelectric Properties of K0.5Na0.5NbO3 Thin Films Derived from Non-alcohol Niobium Salt Sol-gel Process

Lead-free K0.5Na0.5NbO3 (KNN) thin films were prepared on Pt (111) /Ti/SiO2/Si (100) substrates by a polyvinylpyrrolidone (PVP)-modified sol-gel method without any metal alkoxides. The effects of PVP on the crystallization, surface morphology and electrical properties were investigated. It was found that the introduction of PVP into the sol could reduce the annealing temperature, enhance the surface quality and improve the KNN film of (100) oriented growth. Compared with the pure non-PVP-modified KNN thin films, the dielectric and ferroelectric properties of the KNN films were significantly enhanced by adding PVP into the sol. In particular, the PVP-modified KNN films which were annealed at 550°C exhibited relatively saturated polarization-electric field (P-E) hysteresis loops with high remnant polarization Pr of 22 μC/cm2, dielectric constant of 280 and dielectric loss of 0.09, respectively, indicating promising lead-free piezoelectric film candidate for future applications.

Effect of Sn Content on Structure and Properties Near the Morphotropic Phase Boundary in a PbSnO3-PbZrO3-PbTiO3 Ternary System

Piezoelectric ceramics in the PbSnO3-PbZrO3-PbTiO3 (PZST) ternary system with pure perovskite structure were synthesized by a conventional solid state reaction method with the compositions near the morphotropic phase boundary (MPB). The influences of Sn content on dielectric, piezoelectric, and ferroelectric properties of Pb(ZrxSnyTi1−x−y)O3 ceramics were investigated. The experimental results showed that, with increasing the Sn content along the Ti = 0.48 line, the optimized sintering temperature, tetragonality, and Curie temperature (TC) decreased monotonically. The polarization–electric field hysteresis loops show a pinning effect in some low Sn compositions. Frequency dependence of the pinning effect was studied accompanied with current–electric field curve analysis. The PZST compositions near MPB show promising advantages for practical applications.

Low-temperature synthesis of KTa0.55Nb0.45O3 powders and thin films via metal-organic solution

Potassium tantalite niobate powders and thin films were synthesized via metal-organic solution. The synthesized powders and thin films have a tetragonal phase with the perovskite structure. The powders show a cubic shape with sizes in the range of 120–230 nm. The emission spectrum of powders shows emissions peaked at 413, 451 and 468 nm, related to the electron-hole recombination of localized exciton Ta4+–O1− and Nb4+–O1− in a regular octahedron (TaO6 and NbO6). The polarization-electric field hysteresis loop of thin films is rectangular. The current–voltage characteristic of thin films shows a feature of linear to nonlinear transition, which is related to the space-charge-controlled mode of electrical conduction in solids.

Characterizations of epitaxial Bi(Mg1/2Ti1/2)O3–Bi(Zn1/2Ti1/2)O3 solid solution films grown by pulsed laser deposition

(111)-oriented epitaxial (1 − x)Bi(Mg1/2Ti1/2)O3–xBi(Zn1/2Ti1/2)O3 solid solution films were grown on (111)cSrRuO3/(111)SrTiO3 substrates by pulsed laser deposition, and their crystal structure and electrical properties were characterized. The solid solution films consisted of a perovskite single phase in the x range of 0–0.93. The coexistence region of rhombohedral and tetragonal phases was observed in the x range of 0.18–0.60, which differed from reported data for the powders synthesized at high temperatures and high pressures. The polarization–electric field hysteresis loops originating from ferroelectricity were observed at room temperature and 1 kHz in the x range of 0–0.33, and the remanent polarization monotonously decreased with increasing x. The relative dielectric constant measured at room temperature and 100 kHz and the apparent piezoelectric constant evaluated by piezoresponse force microscopy at room temperature and 5 Hz were maximum at approximately x = 0.14. These results suggest that these tendencies of the electrical and electromechanical properties were related to the volume fractions of the constituent phases in the solid solution films.

Analysis of Hysteretic Behavior in a PBZTS Ceramics by a Preisach Distribution

This paper presents a new way of using the classical Preisach distribution to the analytical description of the behavior of ceramic ferroelectrics in a wide range of temperatures. The iteration method have been used to investigate the Preisach distribution from polarization-electric field hysteresis loops to observe the composition and temperature variation of the some parameters in lead barium zirconate titanate stannate ceramic samples. Received Preisach distributions from P-E hysteresis loops were modeled by selected analytical functions to find useful parameters to observing the evolution of the hysteresis loops with temperature. This type of analysis can allow a more complete understanding of the relaxor properties occurring in these kind of materials, and may be used to examination the changes of temperature changes of piezoelectric sensors.

Growth and investigation of 0.80Na0.5Bi0.5TiO3–0.20K0.5Bi0.5TiO3 lead-free single crystal

Abstract 0.80Na 0.5 Bi 0.5 TiO 3 –0.20K 0.5 Bi 0.5 TiO 3 (80NBT–20KBT) lead-free piezoelectric single crystals have been successfully grown by the self flux method. Structure of the grown NKBT single crystals was confirmed by powder X-ray diffraction analysis. The grown crystal belongs to tetragonal system at room temperature. The lattice strain was calculated from Williamson–Hall relation. The temperature dependence of dielectric constant and loss measurement confirmed that the crystal exhibited relaxor-like behavior which is in consistence with the recent observation by Otanicar et al. [J. Appl. Phys. 113 (2013) 024106]. Polarization-electric field hysteresis loops revealed that the remnant polarization is 12.56 μC/cm 2 and coercive electric field is 29.1 kV/cm.

Complex permittivity scaling of functionally graded composites

In this paper, we provide a fundamental understanding of dielectric loss behavior as a function of applied electric field and frequency in functionally graded composites with varying numbers of layers and compositions. A new power-law scaling relation in the form of was derived based upon the ferroelectric hysteresis. The magnitude of the imaginary component of the dielectric permittivity was estimated from the polarization–electric field hysteresis loop. The changes in exponents of the scaling relation were correlated with the mechanism controlling the dielectric loss and interfacial coupling in graded structures. Building upon the scaling analysis, we investigated the effect of E-field on the domain mobility (μ) for various functionally graded systems. These results were correlated with the experimental investigation on ferroelectric domains using transmission electron microscopy and piezoresponse force microscopy.

Grain size effect on piezoelectric and ferroelectric properties of BaTiO3 ceramics

Abstract A series of dense barium titanate (BaTiO 3 , BTO) ceramics with different grain sizes (GS) were prepared by two-step sintering method. The effect of GS on piezoelectric coefficient ( d 33 ) and planar electromechanical coupling factor ( k p ) displayed a trend similar to that on relative permittivity ( ɛ ′). The values of d 33 , k p , and ɛ ′ increased significantly with decreasing GS, reaching maximum values ( ɛ ′ = 6079, d 33 = 519 pC/N and k p = 39.5%) at approximately 1 μm, and then decreased rapidly with further decreasing GS. The results revealed that high-performance BTO ceramics could be effectively prepared by controlling GS. Polarization–electric field hysteresis loops and temperature dependence of ɛ′ were also investigated.

Synthesis and Properties of Mn-Doped (Bi<sub>0.5</sub>Na<sub>0.5</sub>)TiO<sub>3</sub> Thin Films by Chemical Solution Deposition

Lead-free ferroelectric (Bi0.5Na0.5)TiO3(BNT) thin films were prepared by chemical solution deposition. BNT and Mn-doped BNT precursor thin films crystallized in the perovskite single phase at 700 °C on Pt/TiOx/SiO2/Si substrates. The leakage current density of the perovskite BNT films, especially in the high applied field region, was reduced by doping with a small amount of Mn. Also, Mn doping markedly improved the ferroelectric properties of the films. 0.5 and 1.0 mol% Mn-doped BNT thin films exhibited well-shaped ferroelectric polarization (P) electric field (E) hysteresis loops at room temperature. Furthermore, the 1 mol% Mn-doped BNT films showed a typical field-induced strain loop, and the effectived33values were estimated to be about 60 pm/V.

Epitaxial BiFe0.95Mn0.05O3 thin films on transparent La0.07Ba0.93SnO3 electrodes

By employing conductive and transparent La0.07Ba0.93SnO3 (LBSO) films as bottom electrodes, epitaxial BiFe0.95Mn0.05O3 (BFMO) ferroelectric capacitors were fabricated on SrTiO3(001) [STO(001)] substrates by pulsed laser deposition method. The LBSO films showed an excellent optical transmittance in the visible range and a weak metallic conductive behavior, with the room-temperature resistivity, carrier concentration, and mobility of 1.223mΩcm, 5.54×1021cm−3, and 0.923cm2/Vs, respectively. X-ray photoelectron spectroscopy and X-ray absorption near-edge structure spectra analysis revealed that iron ions were present primarily as Fe3+ in BFMO films. The band gap of BFMO films was determined to be 2.63eV from the optical transmittance of the BFMO/LBSO/STO(001) heterostructures. Pt/BFMO/LBSO/STO(001) structured ferroelectric thin-film capacitors showed well-saturated rectangular-shaped polarization–electric field hysteresis loops with the remanent polarization of 45μC/cm2 at a measurement frequency of 1kHz, indicating that the perovskite-type LBSO films can be potentially used in transparent devices especially based on all-perovskite heterostructures.

Relaxor behavior and energy storage performance of ferroelectric PLZT thin films with different Zr/Ti ratios

Abstract Ferroelectric lead lanthanum zirconate titanate (PLZT) films with 8 mol% lanthanum and different Zr/Ti ratios (70/30, 65/35, 58/42, 52/48, 45/55, and 40/60) have been grown on platinized silicon substrates by chemical solution deposition. The effects of the Zr/Ti ratios on the dielectric and ferroelectric properties were investigated for high-power energy storage applications. These films exhibited relaxor behavior and slim polarization–electric field hysteresis loops, and the degree of phase transition diffuseness decreased with increasing Ti. The PLZT films with Zr/Ti=52/48 had a high spontaneous polarization of ≈51.2 μC/cm 2 , a low remanent polarization of ≈9.1 μC/cm 2 , and a low coercive electric field of ≈25.9 kV/cm, leading to a recoverable energy density of ≈30 J/cm 3 and a charge–discharge efficiency of ≈78% at room temperature. The high energy density and high efficiency indicate that relaxor PLZT with La/Zr/Ti=8/52/48 is a promising candidate for high-power film capacitors.

Piezoelectric Properties of Fine-Grained Pb(Mg1/3Nb2/3)O3–Pb(Zr,Ti)O3–Bi(Zn1/2Ti1/2)O3 Quaternary Solid Solution Ceramics

On the basis of solid state reaction eutectic behavior between Pb(Mg1/3Nb2/3)O3–Pb(Zr,Ti)O3 (PMN–PZT) and metastable perovskite-type Bi(Zn1/2Ti1/2)O3 (BZT), perovskite-structured PMN–PZT–BZT quaternary solid solution piezoceramics with various compositions were experimentally demonstrated with an intrinsic low sintering temperature in the windows of 950–1050 °C. These fine-grained densified PMN–PZT–BZT ceramics were able to be poled sufficiently at room temperature through polarization–electric field hysteresis loop measurement, different from normal poling treatment with DC bias field at high temperature, which will simplify future device processing of monolithic multilayer piezoceramic transducers. A typical piezoelectric property of dielectric constant ε33T/ε0 = 3471, piezoelectric constant d33 = 480 pC/N, planar coupling coefficient kp = 0.41, thickness coupling coefficient kt = 0.50, mechanical quality factor Qm = 68 and relaxor ferroelectric phase transition temperature Tm = 167 °C at 1 MHz was obtained for the fine-grained densified Pb0.96Sr0.04(Mg1/3Nb2/3)0.37Zr0.24Ti0.39O3+3%Bi(Zn0.5Ti0.5)O3+2%NiO ceramics sintered at 1020 °C, which is much promising to manufacture monolithic multilayer piezoelectric transducers with Ag95/Pd5 as inner electrode material.

Polarization switching kinetics in ultrathin ferroelectric barium titanate film

The investigation of polarization switching kinetics in an ultrathin barium titanate film reveals true threshold switching at a large coercive electric field, evidence that switching is of intrinsic thermodynamic nature, rather than of extrinsic nature initiated by thermal nucleation, which has no true threshold field. The switching speed of a 7nm thick epitaxial film exhibits a critical slowing as the threshold is approached from above, a key characteristic of intrinsic switching. In contrast, a bulk crystal exhibits nucleation-initiated switching, which has no threshold, and proceeds even at fields well below the nominal coercive field, which was determined independently from the polarization-electric field hysteresis loop. Previously, this phenomenon was only reported for ultrathin ferroelectric polymer Langmuir–Blodgett films. Since both the thermodynamic coercive field and the intrinsic switching kinetics are derived from the mean field theory of ferroelectricity, we expect that these phenomena will be found in other ferroelectric films at the nanoscale.

W-doping induced antiferroelectric to ferroelectric phase transition in PbZrO3 thin films prepared by chemical solution deposition

We reported on W-doping induced antiferroelectric to ferroelectric phase transition in PbZrO3 (PZO) thin films prepared on Pt/Ti/SiO2/Si substrates by a chemical solution deposition method. The phase transition has been studied through polarization-electric field hysteresis loop, capacitance-voltage characteristic, and Raman scattering measurements. Suitable amount W-doping increased the saturated polarization of antiferroelectric W-doped PZO thin films, whereas the ferroelectric W-doped PZO thin films exhibited higher dielectric constant with a high dielectric-bias voltage tunability of about 70%. With increasing W-doping content, the orientation of the thin films changed from preferred (111)Cubic to complete (100)Cubic, due to W-doping-induced lattice distortion, meanwhile the Curie temperature dropped, and dielectric maximum broadened. Our study demonstrates that W-doping is an effective way to tailor the electrical properties of PZO thin films through the induced antiferroelectric-ferroelectric phase transition.

Squareness Control in Polarization–Electric Field Hysteresis Curves in Rhombohedral Pb(Zr,Ti)O3 Films

Squareness in polarization–electric field hysteresis loops of (100)-oriented epitaxial and fiber-textured rhombohedral Pb(Zr,Ti)O3 films prepared on (100) SrTiO3 and (100) Si substrates, respectively, was investigated as a function of temperature. The ratio of remanent polarization to saturation polarization (Pr/Psat) decreased with increasing temperature for all films. It depends on the kind of substrates and the remained strain in the in-plane orientation. These data suggest that the existing strain in the films possibly affects the temperature dependence of the Pr/Psat ratio.

Effect of sintering temperature on internal‐bias field and electric properties of 0.2PZN–0.8PZT ceramics

AbstractPiezoelectric ceramics system of Pb((Zn1/3Nb2/3)0.20–(Zr0.50Ti0.50)0.80)O3 (0.2PZN–0.8PZT) was prepared by the conventional oxide mixing method. The dependences of the internal‐bias field and electric properties on the sintering temperature were investigated systematically. The results indicated that the perovskite structure was stable in a wide sintering temperature region. The rise of sintering temperature favored the enlargement of the grain size, while showing a slight effect on tetragonal distortion c/a. The dissymmetrical shape of polarization–electric field hysteresis loops was displayed in all specimens, indicating the existence of internal‐bias field (Ei). With the increase of sintering temperature, Ei sharply decreased to 0.84 kV cm−1 at 1000 °C then increased, while the remnant polarization (Pr) was found to show the inverse trend. The derivative effects of the sintering temperatures, involving the internal‐bias field effect and grain‐size effect, affected the ferroelectric and piezoelectric properties of 0.2PZN–0.8PZT.

Distribution of pyrochlore phase in Pb(Mg1/3Nb2/3)O3-PbTiO3 films and suppression with a Pb(Zr0.52Ti0.48)O3 interfacial layer

Thin films of the relaxor ferroelectric Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) on Pt/Ti/SiO2/Si (Pt/Si) substrates both with and without a Pb(Zr0.52Ti0.48)O3 (PZT) interfacial layer were investigated. Perovskite and pyrochlore coexistence was observed for PMN-PT thin films without a PZT interfacial layer. Interestingly, most of the pyrochlore phase was observed in single-coated films and in the first layer of multi-coated films. The pyrochlore phase exhibited grains with an average size of about 25nm, which is smaller than those of the perovskite phase (about 90nm). In contrast, for PMN-PT thin films grown on a PZT interfacial layer, the formation of a pyrochlore phase at the interface between PMN-PT layers and the substrate is completely suppressed. Moreover, small grains are not observed in the films with a PZT interfacial layer. The measured polarization-electric field (P-E) hysteresis loops of PMN-PT films with and without PZT layers indicate that enhanced electrical properties can be obtained when a PZT interfacial layer is used. These enhanced properties include an increase in the value of remanent polarization Pr from 2.7 to 5.8μC/cm2 and a decrease in the coercive field Ec from 60.5 to 28.0kV/cm.

Properties of flexible, transparent barium titanate nanoparticle/poly(2-hydroxyethyl methacrylate) hybrid

A transparent BaTiO3 particle/poly(2-hydroxyethyl methacrylate) (PHEMA) hybrid was synthesized from a Ba–Ti double alkoxide modified with an organic ligand, and the refractive index and ferroelectric properties of the hybrid were studied. The transparent hybrid was flexible and could be shaped not only in the form of thin films on substrates but also in the form of flexible self-standing films. BaTiO3 particles around 5 nm in diameter were dispersed uniformly in the polymer matrix. The refractive indexes of the hybrid films increased with decreasing wavelength and were dependent on the volume fractions of the BaTiO3 and polymer phases. The hybrid film synthesized at a molar ratio of BaTiO3:2-vinlyloxyethanol:H2O:PHEMA = 1:8:30:5 gave the best result, with a refractive index of 1.55 at 589 nm and an Abbe number of 37.5. A transparent hybrid film on platinized silicone substrates exhibited a polarization–electric field hysteresis loop.

Large and uniform piezoresponse of BiFe0.995W0.005O3 thin film annealed at 450 °C

BiFe0.995W0.005O3 films were epitaxially deposited on LaNiO3(100)/Si substrates using a metal organic decomposition process at the annealing temperatures below 500 °C. X-ray diffraction measurement reveals that the film can be well crystallized at an annealing temperature as low as 450 °C. The leakage current analysis indicates that the content of grain boundaries in the films is a dominant factor affecting the leakage currents of the BiFe0.995W0.005O3 films. Well saturated polarization–electric field hysteresis loops can be obtained in all the crystallized BiFe0.995W0.005O3 films due to their low leakage currents. The film annealed at 450 °C exhibits a large remanent piezoelectric coefficient d33 (128 pm/V), which is comparable to that obtained in the BiFe0.99W0.01O3 film annealed at 500 °C. Additionally, the most uniform piezoresponse can be observed in the BiFe0.995W0.005O3 film annealed at 450 °C among all the crystallized films, which can be explained by the uniform domain structure and effective electric field applied on the film owing to the homogeneous grain size in the film.