Ni/Pb(Zr,Ti)O3/TbFe2层状复合材料的谐振磁电特性研究

采用化学镀和黏接法制备层状磁电复合材料Ni/PZT/TbFe₂,研究其磁电性能及谐振频率随Ni层厚度的变化情况. 结果表明:Ni/PZT/TbFe₂层状磁电复合材料与其他结构的磁电性能不同,其一阶弯曲谐振峰值和纵向谐振峰值都很大. 随着Ni层厚度的增加,Ni/PZT/TbFe₂层状磁电复合材料的一阶纵向谐振峰值逐渐增大. 结合实验数据和理论计算值得出了材料的一阶弯曲谐振频率fr1和一阶纵向谐振频率f 关键词： 磁电效应 正磁致伸缩 负磁致伸缩 谐振频率     

Multiferroic and magnetoelectric properties of MnFe2O4/(Pb0.8Sr0.2)TiO3 composite films

Abstract

MnFe₂O₄/(Pb_0.8Sr_0.2)TiO₃ (MFO/PST20) heterostructured composite films with three different structures have been grown on Pt/TiO₂/SiO₂/Si substrates by metal–organic decomposition processing via spin coating technique. The structural analysis revealed that the crystal axes of the MnFe₂O₄ are aligned with those of the PST20 ferroelectric matrix with obvious interfaces and no diffusions exist in all the three composite films. These composite films exhibit simultaneously multiferroic and magnetoelectric responses at room temperature. The growth structure of MFO and PST20 layers has an effect on multiferroic and magnetoelectric coupling behaviours of the composite films. The bi- and four-layered MFO/PST20 composite films exhibit superior ferroelectric properties compared to the tri-layered film. The increasing MFO and PST20 layers in the composite films enhance ferromagnetic properties and are closely related to the strain release in MnFe₂O₄ phase. The MFO/PST20 bi-layered composite film shows a high magnetoelectric voltage co-efficient α_E ~ 194 mVcm^?1Oe^?1 at a dc magnetic field H_dc ~ 2.5 kOe. A significant decrease in α_E value has been observed for tri- and four- layered composite films. A close correlation between phase selective residual stress and magnetoelectric properties has been emerged. The results are reasonably encouraging for employing MnFe₂O₄ for growing multiferroic–magnetoelectric composite films.     

单磁场驱动的Tb1-xDyxFe2-y/Pb(Zr,Ti)O3三层膜磁电效应

研究了Tb1-xDyxFe2-y(TDF)与锆钛酸铅(PZT)三层膜样品的制备和在单一直流磁场驱动下的磁电(ME)效应.在该系列三层膜样品中测量到了巨大的ME耦合效应.所得实验结果与同种样品在两磁场驱动下的ME效应完全不同.这可能预示了某些新的物理内容.该技术可简化ME效应在某些实际应用中的复杂度.     

Terfenol-D/Pb(Zr,Ti)O3 Disk-Ring Multiferroic Heterostructures Coupled Through Normal Stresses

Disk-ring multiferroic heterostructures composed of Terfenol-D and Pb(Zr,Ti)O₃ (PZT) were prepared and characterized, for which the ferromagnetic and ferroelectric phases were coupled through normal stresses instead of the shear stresses that acted in most of the previous multiferroic heterostructures. High low-frequency magnetoelectric coefficients of 0.10–0.75 V cm⁻¹ Oe⁻¹ were attained for the disk-ring heterostructures, which indicated the strong magnetoelectric coupling. Moreover, a symmetrical resonant peak was observed for dE ₃/dH ₃ in the frequency range of 1–200 kHz, while another weak peak with asymmetrical shape also existed at a lower frequency for dE ₃/dH ₁, which was due to the combination of two vibration modes.     

Proton-irradiated Pb(Zr0.52Ti0.48)O3 thick films for flexible non-volatile memory applications

We investigated the ferroelectricity in proton-irradiated flexible Pb(Zr_0.52Ti_0.48)O₃ (PZT) thick films and their non-volatile memory characteristics. The Ni-Cr metal foil substrate allowed high-quality polycrystalline PZT films with flexible functionality to be fabricated using conventional sol-gel and high-temperature annealing methods. The 10-MeV proton-irradiated PZT film exhibited an almost square polarization?electric field hysteresis curve with saturated (P_s) and remnant (P_r) polarizations of 18.9 and 17.0 μC/cm², respectively; which are slightly lower than as-grown PZT with P_s = 28.7 μC/cm² and P_r = 24.3 μC/cm². The P_r did not decrease even after 1000 cycles of continuous bending and unbending at a bending radius of 2.14 mm and decreased slightly to ～80% of its initial value after 10⁵ s. Although the P_r decreased to ～55% after 10¹⁰ cycles, the electric polarization remained switchable under positive and negative electric fields. These characteristics suggest that the flexible PZT films could be utilized in non-volatile memory device applications in environments with high doses of proton irradiation, such as those in aeronautics and nuclear power plants.     

Features of the direct magnetoelectric effect in two-layer Tb0.12Dy0.2Fe0.68-PbZr0.53Ti0.47O3 composites

The transverse magnetoelectric effect in two-layer Tb_0.12Dy_0.2Fe_0.68-PbZr_0.53Ti_0.47O₃ composites with Tb_0.12Dy_0.2Fe_0.68 ferromagnetic layers of various thicknesses are studied over the temperature range of 77 to 423 K at resonant frequencies of the bending oscillations. It is established that for all of the studied composites, the transverse magnetoelectric voltage constant passes at 253 K through a peak whose nature is associated with features of the magnetic constituent of the composites.     

Specific features of the inverse magnetoelectric effect in two-layered Tb0.12Dy0.2Fe0.68-PbZr0.53Ti0.47O3 composites

The two-layered Tb_0.12Dy_0.2Fe_0.68-PbZr_0.53Ti_0.47O₃ magnetoelectric composites have been prepared by the deposition of ferromagnetic layers of different thicknesses from a thoroughly mixed Tb_0.12Dy_0.2Fe_0.68 ferromagnetic powder and an epoxy glue on preliminarily polarized PbZr_0.53Ti_0.47O₃ piezoelectric layers. The dependences of the inverse magnetoelectric effect on the frequency and strength of an electric field, the strength of a constant magnetic field, the thickness of a ferromagnetic layer, the average size of Tb_0.12Dy_0.2Fe_0.68 grains in the ferromagnetic layer, and the temperature have been determined. Conditions for the maximum magnetoelectric response have been established.     

Morphology and microstructure of all-epitaxial ferroelectric tri-layered (Bi,La)4Ti3O12/Pb(Zr0.4Ti0.6)O3/ (Bi,La)4Ti3O12 thin films on SrTiO3(011)

The morphology and microstructure of all-epitaxial (Bi,La)₄Ti₃O₁₂/Pb(Zr_0.4Ti_0.6)O₃/(Bi,La)₄Ti₃O₁₂ (BLT/PZT/BLT) tri-layered ferroelectric films, grown on (011)-oriented SrTiO₃ (STO) substrates by pulsed laser deposition, are investigated by transmission electron microscopy (TEM). X-ray diffraction and electron diffraction patterns demonstrate that the epitaxial relationship between BLT, PZT and STO can be described as ; . Cross-sectional TEM images show that the growth rate of BLT is nearly two times that for PZT at the same growth conditions, and 90° ferroelectric domain boundaries lying on {110} planes are observed in the PZT layer. The 90° ferroelectric domains in the PZT layer extend up to 600 nm in length. Long domains penetrate into the neighboring columnar grain through the columnar grain boundary, whereas others are nucleating at the columnar grain boundaries. The roughness of the PZT/BLT interfaces appears to depend on the viewing direction, i.e., it is different for different azimuthal directions. Planar TEM investigations show that the grains in the top BLT layer have a rod-like morphology, preferentially growing along the [110]_BLT direction. The grain width is rather constant at about 90 nm, whereas the length of the grains varies from 150 to 625 nm. These morphological details point to the important role the crystal anisotropy of BLT plays for the growth and structure of the tri-layered films. PACS 81.15-z; 68.37.Lp; 77.84.-s     

Nanosecond domain wall dynamics in ferroelectric Pb(Zr, Ti)O(3) thin films

Domain wall motion during polarization switching in ferroelectric thin films is fundamentally important and poses challenges for both experiments and modeling. We have visualized the switching of a Pb(Zr, Ti)O(3) capacitor using time-resolved x-ray microdiffraction. The structural signatures of switching include a reversal in the sign of the piezoelectric coefficient and a change in the intensity of x-ray reflections. The propagation of polarization domain walls is highly reproducible from cycle to cycle of the electric field. Domain wall velocities of 40 m s(-1) are consistent with the results of other methods, but are far less than saturation values expected at high electric fields.     

Direct magnetoelectric effect in two-layer composite structures Tb0.12Dy0.2Fe0.68-PbZr0.53Ti0.47O3 at bending and longitudinal vibrations

The direct magnetoelectric effect has been studied in samples of two-layer composites containing 8 × 6 × 0.3-mm layers of the piezoelectric material PbZr_0.53Ti_0.47O₃ and 6 × 6 × A-mm layers (A = 0.3, 0.6, 0.9, 1.2, and 1.5) of the ferromagnet Tb_0.12Dy_0.2Fe_0.68 and epoxy adhesive in the frequency range of 10–253 kHz at room temperature. It has been found that the magnetoelectric effect significantly increases at resonance frequencies (13.2–61.1 kHz) of the first harmonic of bending vibrations along the sample length, at resonance frequencies (39.5–90.7 kHz) of the first harmonic of bending vibrations along the sample width, and at resonance frequencies (123.3–141.0 kHz) of the first harmonic of longitudinal vibrations along the sample length. The magnetoelectric effect magnitudes at the resonance frequencies of the bending vibrations is found to be greater than that at the resonance frequencies of the longitudinal vibrations of the sample.     

Epitaxial Pb(Zr,Ti)O3 ultrathin films under open-circuit electrical boundary conditions

The temperature-versus-misfit-strain phase diagram of Pb(Zr,Ti)O3 ultrathin films under open-circuit electrical boundary conditions is simulated via the use of an effective Hamiltonian. Two novel phases, both exhibiting dipolar nanodomains and oxygen octahedral tilting, are discovered. The interplay between dipolar, antiferrodistortive, alloying, and strain degrees of freedom induces several striking features in these two phases, such as the chemical pinning of domain walls, the enhancement of oxygen octahedral tilting near the domain walls, and the existence of dipolar waves and cylindrical dipolar chiral bubbles.     

In-situ X-ray microdiffraction analysis of local strain-field across the interface in a Pb(Zr0.52Ti0.48)O3/Ni0.8Zn0.2Fe2O4/Pb(Zr0.52Ti0.48)O3 tri-layered structure

We have performed a synchrotron X-ray microdiffraction to investigate the variation of the local strain-field across the interface in Pb(Zr_0.52Ti_0.48)O₃/Ni_0.8Zn_0.2Fe₂O₄/Pb(Zr_0.52Ti_0.48)O₃ (PZT–NZFO–PZT) tri-layered structure. In this study, we show that the in-plane lattice parameters of the NZFO lattice depend strongly on the piezoelectric strain of the PZT layer. This result explains that an electric-field-induced piezoelectric strain from the PZT layer is effectively transferred to the NZFO layer. Furthermore, the local strain persists within 20 μm away from the interface, inducing changes of magnetic responses via the inverse magnetostrictive effect.     

Transparent ferroelectric ceramics PbMg1/3Nb2/3O3-xPbZr0.53Ti0.47O3: Dielectric and electro-optical properties

Lanthanum-free high-transparency ferroelectric ceramics PbMg_1/3Nb_2/3O₃?xPbZr_0.53Ti_0.47O₃ (PMN-xPZT) have been prepared for the first time by a two-stage sintering method. The dielectric and electro-optical properties of the PMN-xPZT ceramics of different compositions, with the values of x both far from the morphotropic phase boundary (x = 10, 16, 23%) and close to it (x = 33%), have been studied. It has been shown that, in compositions lying closer to the morphotropic phase boundary (x = 23 and 33%), one observes, with no electric field applied, a first-order phase transition to a macrodomain ferroelectric phase, whereas the compositions far from the boundary (x = 10, 16%) persist in the relaxor cubic phase down to the low-temperature domain. It has been found that, in the ceramic with x = 33%, the quadratic electro-optical coefficients have at high temperatures (T > 340 K) the largest value among the relaxor systems, which expands the temperature interval of applicability of these solid solutions in industry.     

Tetragonal distortion and the domain structure of thin Pb(Zr,Ti)O3/MgO(100) films

3 /MgO(100) films was studied in synchrotron X-ray scattering experiments. In the thin epitaxial films, the tetragonal distortion of the ferroelectric phase and the transition temperature were significantly reduced. In sharp contrast to the reported mixture of the a-type and the c-type domains in thicker films, the 250-Å-thick film was purely composed of the c-type domains in the tetragonal phase. We attribute the suppression of the transition to the substrate effect, which prefers the c-type domains near the interface, and reduces the tetragonal distortion to minimize the strain energy caused by the lattice mismatch. Received: 1 November 1997/Accepted: 5 January 1998     

Pb(Zr0.3Ti0.7)O3铁电薄膜激光感生电压效应

采用脉冲激光沉积(PLD)技术在LaSrAlTaO₃(LSATO),LaAlO₃(LAO)和SrTiO₃(STO)的单晶倾斜衬底上成功制备了Pb(Zr_0.3Ti_0.7)O₃(PZT)薄膜,在三种倾斜衬底上生长的PZT薄膜中都首次发现了LIV效应.对PZT/LSATO薄膜在a,c轴两种不同取向择优生长下的LIV效应做了研究,发现在薄膜c轴取向择优生长 关键词： 激光感生电压效应 铁电薄膜 薄膜生长取向 原子层热电堆     

Excimer laser-induced transformation in laser ablated Pb(Zr0.52Ti0.48)O3 amorphous thin films

Pb(Zr_0.52Ti_0.48)O₃ (PZT) amorphous thin films were deposited on Si substrates at room temperature and 573?K by pulsed laser deposition. The as-deposited films were subsequently annealed at various laser power densities using a KrF pulsed excimer laser irradiation to induce the phase transformation from amorphous to ferroelectric perovskite structure. Structural analysis shows the possibility of transformation from pyrochlore to perovskite transformation when irradiated above a laser power density of 1.4?MW/cm², which is in agreement with the thermal simulation. The surface quality of the PZT films deposited on 573?K is remarkably superior to that deposited at room temperature due to the enhanced thin structure and composition homogeneity. Almost all the pyrochlore phase transformed into perovskite structure after annealing at 2.8?MW/cm² for 120?s for both PZT films deposited at room temperature and 573?K, respectively. P-E hysteresis measurement of the laser-treated PZT shows relatively low remnant polarization P _r of about 1.2?μC/cm².     

Domain wall creep in epitaxial ferroelectric Pb(Zr(0.2)Ti(0.08)O(3) thin films

Ferroelectric switching and nanoscale domain dynamics were investigated using atomic force microscopy on monocrystalline Pb(Zr(0.2)Ti(0.8))O(3) thin films. Measurements of domain size versus writing time reveal a two-step domain growth mechanism, in which initial nucleation is followed by radial domain wall motion perpendicular to the polarization direction. The electric field dependence of the domain wall velocity demonstrates that domain wall motion in ferroelectric thin films is a creep process, with the critical exponent mu close to 1. The dimensionality of the films suggests that disorder is at the origin of the observed creep behavior.     

The piezoelectric effect in Pb[(Fe1/3Sb2/3) x Ti y Zr z ]O3 ceramics

The piezoelectric properties of Pb[(Fe_1/3Sb_2/3) _x Ti _y Zr _z ]O₃ with x + y + z = 1, x = 0.1, y = 0.43–0.48 ceramics have been investigated over a broad temperature range using a resonance technique. The influence of modification of PZT normal ferroelectric synthesized near the morphotropic phase boundary by a relaxor Pb(Fe_1/3Sb_2/3)O₃ compound on its physical properties was studied. The coefficients s ₁₁, k ₃₁, and d ₃₁ were calculated from the parameters characterizing the behavior of damped harmonic oscillator in the vicinity of the piezoelectric resonance. Several anomalies of the piezoelectric coefficients have been found in the temperature range 300–600 K. Two diffuse phase transitions were observed in Pb[(Fe_1/3Sb_2/3) _x Ti _y Zr _z ]O₃. The anomaly near 530 K for y = 0.43 is responsible for the transition from the rhombohedral phase to the tetragonal one. For y > 0.44 this transition is found to be very diffuse and the coexistence of rhombohedral and tetragonal phases occurs. The observation of low piezoelectric activity confirms the existence of polar regions in Pb[(Fe_1/3Sb_2/3) _x Ti _y Zr _z ]O₃ above T _m.     

Facile preparation and performance of novel high-TC xBi(Ni1/2Ti1/2)O3-(1-x)Pb(Zr1/2Ti1/2)O3 piezoceramics

High Curie temperature (T_C) xBi(Ni_1/2Ti_1/2)O₃-(1-x)Pb(Zr_1/2Ti_1/2)O₃ (xBNT-(1-x)PZT, BNT-PZT) piezoelectric ceramics were prepared by the conventional ceramic processing. The composition-induced morphotropic phase boundary (MPB) and its influences on structure and electrical performance were investigated. The synthesized BNT-PZT ceramics exhibit rather pure perovskite structure, and densified microstructure morphology with uniform elementals distribution in both grains and grain boundaries. With increasing the content of Bi(Ni_1/2Ti_1/2)O₃ (BNT), crystal structure of the BNT-PZT ceramics transform from tetragonal phase to rhombohedral phase, and dielectric response peaks change from narrow shape to very broad shape but all presenting dielectric frequency dispersion. The diffused and relaxation dielectric behavior can be fitted well by the quadratic law, and the Vogel-Fulcher law fitting provides additional information on the relaxation characteristic. The MPB effects are confirmed further by ferroelectric and piezoelectric properties measurements. High-T_C combined with excellent piezoelectric performance can be realized in the BNT-PZT system, which presents promising applications in geothermal exploration, aerospace and related elevated temperatures fields.