Lanthanum-modified Lead Zirconate Titanate Research Articles

Process-Controlled Domain Switching and Improved Ferroelectric Properties in Lanthanum-Modified Lead Zirconate Titanate Films

Process-Controlled Domain Switching and Improved Ferroelectric Properties in Lanthanum-Modified Lead Zirconate Titanate Films

High Energy Density of Polyvinylidene Fluoride‐Based Composite Films Induced by Anisotropic PLZT Fillers

AbstractWith the rapid development of electronic industry, high‐energy storage density dielectric materials are urgently needed to meet electronic components equipment miniaturized demand. Polymer dielectric materials have the advantages of good flexibility and high breakdown field, however, the energy storage capacity of polymers is limited by its inherent low dielectric constant. To improve the dielectric constant and energy storage density of the polymer material, we synthesized 0D (zero dimension), 1D, 2D lanthanum modified lead zirconate titanate (PLZT) fillers which introduced into polyvinylidene fluoride (PVDF) matrix. The anisotropic of the fillers has obvious improvement on the properties of materials. Compared with 0D fillers, high anisotropic fillers are more effective in enhancing the dielectric performances and energy density of PVDF based composites. The high anisotropic ratios of 2D fillers limit the charge migration toward the electrodes and hold back the growing electric tree during breakdown. Consequently, high breakdown strength (430 MV/m) and high discharge energy density (13.9 J/cm3) for 2D PLZT/PVDF composite films were obtained. This work is of critical significance in making dielectric capacitors for energy storage devices and reveals the influence mechanism for different dimensions fillers on the dielectric and energy storage properties of PVDF based composites.

Impact of annealing on electrocaloric response in Lanthanum-modified lead zirconate titanate ceramic

Over the past decades, there has been significant interest in new cooling technology based on the large electrocaloric effect observed in polymeric and inorganic ferroelectric materials. We report a dramatic impact of annealing on the electrocaloric effect observed by direct measurements in Pb0.88La0.12(Zr0.65Ti0.35)0.97O3 bulk ceramics (12/65/35 PLZT). In addition, the EC response was measured deep in a relaxor part of the PLZT composition phase diagram. After additional one-hour sample annealing at 600 °C, the EC response increased by about six times. Electrocaloric results confirm the existence of the significant electrocaloric response with the EC temperature change (ΔTEC) of 4.5 K at 360 K and 90 kV/cm in an annealed sample. This value exceeds previously obtained maximum ΔTEC values at the same field in perovskite relaxor ferroelectrics such as Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) and 8/65/35 PLZT ceramics. The electrocaloric responsivity ΔT/ΔE = 5.09 × 10−7 Km/V determined at 360 K is among the highest observed in bulk perovskite ferroelectrics at a relatively high electric field of 90 kV/cm.

Time-resolved piezoelectric response in relaxor ferroelectric (Pb0.88La0.12)(Zr0.52Ti0.48)O3 thin films

The domain switching dynamics in a relaxor ferroelectric lanthanum-modified lead zirconate titanate thin film with 12 mol. % La was investigated by time-resolved x-ray diffraction. While most frequently epitaxial thin films are investigated, the present work reports results on a polycrystalline thin film. Asymmetric butterfly loops of the strain as a function of the applied electric field evidenced a built-in electric field oriented toward the thin film–substrate interface. The piezoelectric coefficient d33 (in the film reference frame) diminishes with the increasing frequency of an applied AC electric field. From the strain transient during the application of positive-up negative-down voltage pulse sequences with frequencies of up to 100 kHz, characteristic times of the order of 100–200 ns were determined for these relaxor ferroelectric thin films. While switching times ranging from the picosecond to the millisecond range are reported in the literature for different materials, these characteristic switching times are comparable to epitaxial lead zirconate titanate thin films of various compositions despite the polycrystallinity of the present thin film. However, the evidenced built-in electric field significantly influences the switching behavior for different polarities.

Nd3+ emissions in transparent ferroelectric ceramic hosts under ultraviolet excitation

This work investigates the optical response of two Nd-doped relaxor ferroelectric ceramics, PLZT (lanthanum modified lead zirconate titanate) and PLMN-PT (lanthanum modified lead magnesium niobate – lead titanate). The electrical induced birefringence characterization evaluates the nonergodic to ergodic transition, and the Kerr response from 100 K to 600 K. UV-VIS optical absorption showed the presence of well-diluted ions in the valence +3. Photoluminescence measurements (PL) excited in the ultraviolet (UV) range (λ = 325 nm) evidenced three channels of emissions: the fundamental 4F3/2 → 4I9/2 and the transitions between excited levels associated with Nd3+, and the host Ti–O band. Temperature-dependent PL allowed a qualitative and quantitative analysis of the role of these optical emissions channels. Besides, intensity-dependent microphotoluminescence evidenced the character of the ionic and continuum nature of these emissions. At the same experimental conditions, a tendency of emission saturation at high UV excitation in PLMN-PT can be attributed to a slower mechanism of optical transitions than that of PLZT neodymium host.

Impact of Annealing on Electrocaloric Response in Lanthanum-Modified Lead Zirconate Titanate Ceramic

Impact of Annealing on Electrocaloric Response in Lanthanum-Modified Lead Zirconate Titanate Ceramic

A novel vacuum/oxygen hot press sintering approach for the fabrication of transparent PLZT (7.4/70/30) ceramics

Transparent Lanthanum-modified lead zirconate titanate ceramics (PLZT 7.4/70/30) with low content of excess lead oxide (PbO) were successfully prepared by a novel vacuum/oxygen hot press sintering process. The phase structure, microstructure, electrical properties and electro-optic scattering performance of PLZT ceramics as a function of excess PbO in the starting powders have been studied and analyzed. As a result, these ceramics exhibited an ultra-high optical transmittance (>69.4% at 1064 nm; thickness 1 mm) from visible to near-infrared wavelength. Herein, we significantly reduce the use of PbO as an auxiliary agent for sintering. This puts forward a good route to meet the objectives of environmental protection and sustainable development.

Large Quadratic Electro-Optic Effect of the PLZT Thin Films for Optical Communication Integrated Devices

Developing large electro-optic (EO) effect material is crucial technology for developing current levels of optical communication, and the lanthanum-modified lead zirconate titanate (PLZT) transpare...

Investigating the antiferroelectric-ferroelectric phase switching time in lanthanum-modified lead zirconate titanate transparent ceramics by using the electrically induced light scattering effect

A method for achieving the accurate measurement of the antiferroelectric-ferroelectric (AFE-FE) phase switching time based on the electrically induced light scattering effect was designed. The AFE-FE switching times of lanthanum-modified lead zirconate titanate (PLZT) transparent ceramics decreased with the increase of the applied electric fields, and the logarithm of the switching time was approximately proportional to the electric field reciprocal. The random orientation of the polycrystalline structures with dispersion-distributed mixed phases of the PLZT transparent ceramics was the intrinsic mechanism affecting the corresponding switching times in the applied electric field. The smaller electrode size samples switched faster than the larger samples in the same electric field. The size effect of the switching times occurred due to the higher dielectric constant of the ceramics and the parameters of the test circuit, and the larger capacitance of the samples resulted in a longer rising time of the applied electric field, which in turn slowed down the phase switching and prolonged the switching time.

Measurement of electro-optical coefficients based on the Stokes vectors

A method based on the Stokes vectors was developed for the measurement of electro-optical (EO) coefficients, and the detailed test principle, experimental apparatus and data processing were described. The practicability of this method was illustrated by the determination of the EO coefficient of lanthanum-modified lead zirconate titanate (PLZT) transparent ceramics, and the measurement results indicated that the standard deviation values of the EO coefficients obtained by the Stokes vector method was almost half of that of the values measured using the Sénarmont compensator method. The apparatus used for the Stokes vector method consists of only a few optical elements and was easy to adjust and calibrate, thereby enabling scientific, accurate, and efficient EO coefficient measurements for the development of EO materials and devices.

Piezoelectric Properties of Pb1-xLax(Zr0.52Ti0.48)1-x/4O3 Thin Films Studied by In Situ X-ray Diffraction.

The piezoelectric properties of lanthanum-modified lead zirconate titanate Pb1−xLax(Zr0.52Ti0.48)1−x/4O3 thin films, with x = 0, 3 and 12 mol% La, were studied by in situ synchrotron X-ray diffraction under direct (DC) and alternating (AC) electric fields, with AC frequencies covering more than four orders of magnitude. The Bragg reflections for thin films with low lanthanum concentration exhibit a double-peak structure, indicating two contributions, whereas thin films with 12% La possess a well-defined Bragg peak with a single component. In addition, built-in electric fields are revealed for low La concentrations, while they are absent for thin films with 12% of La. For static and low frequency AC electric fields, all lanthanum-modified lead zirconate titanate thin films exhibit butterfly loops, whereas linear piezoelectric behavior is found for AC frequencies larger than 1 Hz.

Electrocaloric response in lanthanum-modified lead zirconate titanate ceramics

Recent findings of a large electrocaloric (EC) effect in polymeric and inorganic ferroelectric materials open a potential possibility of development of solid-state cooling or heating devices of new generation with better energy efficiency that may be less harmful for the environment. We investigate by using direct measurements, the temperature and electric field dependence of the electrocaloric response in Pb1-xLax(ZryTi1-y)1-x/4O3 bulk ceramics (PLZT) with x = 0.06 and 0.12. Here, the properties of the EC response were probed in a part of the PLZT composition phase diagram with low y = 0.40 composition, in which the EC effect was not previously studied. Measurement results show the existence of the sizeable EC response in the 12/40/60 PLZT sample with the EC temperature change (ΔTEC) of 2.92 K at 430 K and 80 kV/cm. This value exceeds previously obtained ΔTEC values in relaxor ferroelectric x/65/35 PLZT compositions, rivaling the best EC response in lead magnesium niobate-lead titanate ceramics. The electrocaloric responsivity (ΔT/ΔE) value of 0.41 × 10−6 Km/V determined at a lower electric field of 20 kV/cm and 410 K is comparable to those observed in other perovskite ferroelectrics.

Photonic integration based on a ferroelectric thin-film platform

Photonic-integrated circuits (PICs) using ferroelectric materials are expected to be used in many applications because of its unique optical properties such as large electro-optic coefficients. In this study, a novel PIC based on a ferroelectric thin-film platform was designed and fabricated, where high-speed optical modulator, spot-size converters (SSCs), and a variable optical attenuator (VOA) were successfully integrated. A ferroelectric lanthanum-modified lead zirconate titanate (PLZT) thin film was epitaxially-grown by using a modified sol-gel method, and it exhibits large electro-optic coefficients (>120 pm/V) and low propagation loss (1.1 dB/cm). The optical modulator, a Mach-Zehnder type, exhibited a half-wave voltage (Vπ) of 6.0 V (VπL = 4.5 Vcm) and optical modulation up to 56 Gb/s. Also, the VOA (with attenuation range of more than 26 dB) was successfully integrated with the modulator. As a result, it is concluded that the developed ferroelectric platform can pave the way for photonic integration.

An optimization dust-removing electrode design method aiming at improving dust mitigation efficiency in lunar exploration

The photovoltaic lunar dust removal technology has proved to own potential application for future space exploration. In this new technology, based on the high voltage characteristics of the photoelectric material lanthanum-modified lead zirconate titanate (PLZT), a dust-removing electrode is used to polarize and remove the lunar dust. The influence of the area and the shape of the dust-removing electrode on the dust removal performance is analyzed in this paper. An optimization of dust-removing electrode design method is proposed and comb-shaped electrodes are designed to improve the dust mitigation efficiency of the system. The configuration of the comb-shaped electrode is optimized by theoretical analysis. A series of experiments are performed to reveal the influence of different factors, such as electrode area, electrode shape, light intensity, copper foil thickness, insulation film and geometric parameters of electrode, etc. on the dust removal performance. Research results of this work can serve as guidelines for optimization electrode design to maximize the efficiency of this photovoltaic lunar dust removal system for future lunar exploration.

Experiments on dust removal performance of a novel PLZT driven lunar dust mitigation technique

Lunar dust removal has proved to be one of the most important issues to be solved in lunar exploration. A novel lunar dust removal technique based on the anomalous photovoltaic effect of lanthanum-modified lead zirconate titanate (PLZT) has been developed in our previous research which could be used for conductor surface dust mitigation. In this study, the working performance of this novel dust removal technique is investigated. Since the particle size of the dust has a strong influence on the lunar dust removal performance, the particle size range which is applicable for this technique is explored first. Then the relation between the dust particle size and charge is discussed theoretically and experimentally. An experimental platform is built up for testing the working performance of this technique and the results indicate that a 95% dust removal efficiency can be achieved on a 320 mm × 125 mm dust covered surface, which is very promising for future lunar dust mitigation.

Depth dependent ferroelectric to incommensurate/commensurate antiferroelectric phase transition in epitaxial lanthanum modified lead zirconate titanate thin films

Transmission electron microscopy was used to investigate the coexistence of ferroelectricity (FE) and antiferroelectricity (AFE) in (001) and (011) (Pb0.97, La0.02) (Zr0.95, Ti0.05) O3 (PLZT) epitaxial thin films. The depth resolved selected area electron diffraction (SAED) results revealed that the AFE phase was located in the near interface region, whereas the FE phase was found in the near surface region. A thickness dependent lattice parameter distribution was calculated using the SAED data, and a decrease in the c/a ratio was found to correlate with the transition from AFE to FE stability. Additionally, commensurate and incommensurate modulations in AFE PLZT were identified based on the observation of various superlattice reflections.

Theoretical and experimental analysis on deflection control of photovoltaic-electrostatic cantilever beam

A model of photovoltaic-electrostatic cantilever beam based on lanthanum-modified lead zirconate titanate ceramic is proposed in this article. New equivalent electrical model of lanthanum-modified lead zirconate titanate ceramic connected to a parallel plate composed of two copper foils is obtained by modifying the original lanthanum-modified lead zirconate titanate equivalent electrical model. After that, the mathematical model of photovoltaic-electrostatic cantilever beam is established. Furthermore, the influences of ultraviolet light intensity and copper foil length on the deflection of the photovoltaic-electrostatic cantilever beam are analyzed via the theoretical and experimental methods. The analysis results indicate that the deflection at the free end of cantilever beam increases with the increase in light intensity and length of the copper foil. The photovoltaic-electrostatic flexible cantilever beam can be taken as a micro-actuator with the advantages of remote control and clean drive.

A new photovoltaic lunar dust removal technique based on the coplanar bipolar electrodes

Lunar dust removal is one of the most important issues to be solved in lunar exploration. A lunar dust removal method based on the anomalous photovoltaic effect of lanthanum-modified lead zirconate titanate has been developed in our previous research which could be used for conductor surface dedusting. In this study, a novel lunar dust removal technique utilizing a couple of coplanar bipolar dust-removing electrodes is proposed. With this technique, lunar dust on different kinds of surface (conductor and nonconductor) can be reliably debrided. The working principle of this technique is introduced first, followed by a series of simulations and experiments which demonstrate that this technique can generate an adequate absorbing force on the lunar dust lying on the insulating or conducting surface and can provide ideal dedusting performance. Effects of electrode area and dust particle size on the dust removal efficiency are investigated. A crawler-type autonomous dust-removing device is developed in which a couple of flexible coplanar bipolar electrodes are designed as the crawler belts of the device. By controlling the path and velocity of the dust-removing device, a 95.3% dust removal rate was achieved in a dedusting test on a 500 × 400 mm2 plank. This study provides a new feasible method for future lunar dust removal mission.

Effects of Bi3+ Doping on the Optical and Electric-Induced Light Scattering Performance of PLZT (8.0/69/31) Transparent Ceramics.

Lanthanum modified lead zirconate titanate (abbreviated as PLZT) Electro-Optical ceramics with various Bi concentration were prepared by a hot-press process. The PLZT ceramic samples all present a single perovskite structure with no second phase detected. Bi3+ ion was considered to mainly enter the A-site of perovskite ABO3 structure of PLZT ceramics by the X-Ray Diffractionanalysis. The maximum permittivity (εm) of the PLZT samples decreased obviously as Bi concentration increased, while their remnant polarization (Pr) decreased slightly. In particular, the PLZT sample with 0.14 wt% Bi doping presented a higher optical transmittance 61.8% (λ = 633 nm), and its electric-induced light scattering performance was found to be improved obviously, the maximum light deduction value of ~47.6% was obtained.

Lanthanum modified lead zirconate titanate thin films by sol-gel and plasma annealing for integrated passive nanophotonic devices

Lanthanum modified lead zirconate titanate (PLZT) thin films were prepared by sol-gel and the plasma annealing process. The PLZT thin films are pure perovskite phase and highly crystalline. The polarization-electric loops confirmed quadratic PLZT thin films. The optical properties were determined by a spectroscopic ellipsometry analyzer, showing an absorption coefficient of near zero and an energy gap of around 3.6 eV. The insertion losses of the optical devices based on PLZT films are less than 5 dB. These films have the potential to be applied in the field of integrated nanophotonic devices.