PLZT Ceramics Research Articles

Sol-Gel Processing and Novel Physical Properties of PLZT 7/57/43 Ferroelectric Ceramics

The sol-gel process was employed to prepare (Pb1-xLax)(Zr1-yTiy)O3 (PLZT) ceramics with nominal composition Pb0.93La0.07(Zr0.57Ti0.43)0.9825O3. The structure and physical properties such as dielectric, piezoelectric and ferroelectric properties were investigated. X-ray diffraction results showed that the perovskite phase PLZT was formed when the sol-gel processed powders was calcined at 600°Cfor 4 hours. nanocrystalline particles with a size of ~50nm were found. TG-DTA studies were used to analyze the thermal properties of nanopowders for understanding the reaction kinetics in them. Wafered bulk ceramic samples prepared from the sol-gel derived powders were subjected to electrical measurements, in order to determine the dielectric, piezoelectric and ferroelectric properties. The dielectric properties of the PLZTBST system are further improved and the dielectric piezoelectric properties of PLZT ceramics are found to be sensitive to the particle size of PLZT nanopowders. The dielectric piezoelectric properties of polarized PLZT ceramics can be improved with the lessening of PLZT nanopowder size. Meanwhile, the grain size of PLZT ceramics decreases.

Investigation on the Structural Properties of a New Prepared 0.2PZS-0.8PLZT Ceramics

View of the importance that has the development in the field of advanced technology transmission in human life, smart materials draws the attention of many researchers. In this contribution, we are interested in synthesizing a new smart material of the ceramic type based on Pb, Zr, Ti (PZT) doped La in the site A, and Sb, Zn in site B from a solid solution of pure oxides. The synthesized samples are thermally treated at 800°C. The techniques of x-ray diffraction (XRD) and SEM (scanning electron microscopy) are used to characterize the microstructure (the crystallographic phase), and the densities of the obtained samples were determined from their weights and volumes. The effect of sintering temperature on the microstructure properties was studied.

Effect of Dy substitution on ferroelectric, optical and electro-optic properties of transparent Pb0.90La0.10(Zr0.65Ti0.35)O3 ceramics

Highly transparent Dy-codoped lead lanthanum zirconate titanate (PLZT) ceramics were sintered from oxide powders by the hot pressing method. The ceramics exhibited a transparency as high as 67% at 632.8nm (close to the theoretical value). The effects of substituting Lanthanum by Dysprosium on the phase structure, microstructure, dielectric, ferroelectric, optical and electro-optic properties of PLZT were examined. The results showed that Dy substitution decreased the coercive field, improved the optical transmittance and electro-optic properties of PLZT ceramics. Moreover, the high half-wave voltage (affecting the working voltage of devices) of PLZT was reduced from 850V to 510V by Dy substitution. Modified PLDZT transparent ceramics are competitive candidate materials for modern optical communication, and the variable optical attenuator (VOA) based on PLDZT exhibited excellent performances.

Complex impedance spectroscopy studies of PLZT (5/52/48) ceramics synthesized by sol–gel route

The polycrystalline perovskite Pb0.95La0.05(Zr0.52Ti0.48)O3 ceramic material was prepared by sol–gel route. Structural, phase formation and thermal properties were confirmed by X-ray diffraction, thermogravimetry and differential thermal analysis. The microstructural study was carried out using scanning electron microscope. The electrical properties of the ceramics were investigated within a wide range of both temperature (from 25 to 500 °C) and frequency (from 100 Hz to 1 MHz) using complex impedance spectroscopy. The impedance spectrum results indicate the decrease in dielectric constant with increase in frequency while the dielectric loss increases with frequency. The activation energy of the sample was calculated as 0.124 eV from the Arrhenius plot of dc conductivity vs. inverse of absolute temperature. The remnant polarization (Pr) and coercive electric fields (Ec) are found out as 5.97 μC/cm2 and 8.89 kV/cm from the ferroelectric loop measured at room temperature.

Technology of PLZT ceramics microfibers for multiferroics composites

Compactness and large energy conversion capacity are the main reasons of development of sophisticated ceramics materials in microfibers form, which are prepared for high-speed multiferroic systems and devices. These multifunctional composite applications are owing to coupling of electrical and magnetic properties, as well as additional thermal and mechanical properties. So that, they are suitable for magnetic sensors, electrically tunable non-linear transducers, and non-volatile memories. In our experiment, the thin fibers ceramics have been produced using special environmental chamber where the high temperature sintering can be protected by controlling such parameters as temperature and sintering atmosphere. Consequently, for these purposes structural and physical properties, preparation and thermal synthesis of micrometer sized lead lanthanum zirconate titanate (PLZT) fibers were investigated thoroughly. Since the phase transition properties of PLZT fibers differ much, the production process of fibers suffers from lack of proper high temperature control. Consequently, our experiments should help to eliminate this drawback, so that various technological conditions, parameters, and subsequent sintering atmosphere with different mixtures of PbO and ZrO were experimentally tested. Final conclusions include comparative analysis of obtained PLZT fibers ferroelectric phase transition properties to specific sintering atmosphere.

Multifunctional Optical Device With Electrooptic Er$^{3 +}$ and Yb$^{3 +}$ Doped Lanthanum-Modified Lead Zirconate Titanate Ceramic Gain Media

A novel multifunctional optical device, combining optical filtering, amplification, attenuation and switching functions in one unit, was designed and demonstrated in covering both C- and L-bands, by taking advantage of excellent electrooptic (EO) property in the gain media of 2.0 mol% Er3+ doped and 2.0 mol%Er3+, 5.0 mol%Yb3+ codoped lanthanum-modified lead zirconate titanate (PLZT) ceramics. In order to optimize the multifunctional device, the absorption and photoluminescence spectra and optical gain profiles of the core components-optically active ceramic variable waveplates were studied experimentally, along with the dielectric, optical, thermal and EO characterization of the typical non-memory ceramic plates. This work has paved a way leading to a broader spectrum of applications, specifically in constructing monolithic, array- and microchip-based devices and systems, with erbium and other rare earth doped PLZT ceramics as both gain media and electrically variable waveplates.

Diffuse critical point in PLZT ceramics

The ferroelectric transition line in the electric-field temperature phase diagram of the canonical relaxor ferroelectric ceramics 9/65/35 PLZT has been studied via polarization and high-resolution heat capacity measurements. The modified calorimetric relaxation measurements show a change of the sample temperature if the applied electric field is sufficiently high to induce a ferroelectric transition. The anomaly in the sample temperature is a consequence of the released excess heat, i.e., latent heat at the transition from the disordered dipolar glass state to the long-range–ordered ferroelectric state. The presence of latent heat supports the well-established physical picture of relaxors according to the so-called dipolar glass scenario. Furthermore, it was found that latent heat decreases with increasing temperature, indicating the existence of a diffuse-type critical point.

Pyroelectric energy conversion using PLZT ceramics and the ferroelectric–ergodic relaxor phase transition

This paper is concerned with direct conversion of waste heat into electricity by executing the Olsen cycle on lead lanthanum zirconate titanate (PLZT) ceramics undergoing a relaxor–ferroelectric phase transition. The Olsen cycle consists of two isothermal and two isoelectric field processes. First, the temperature-dependent dielectric properties were measured for x/65/35 PLZT. The polarization transition temperature of x/65/35 PLZT was found to decrease from 240 to 10 °C as x increased from 5 to 10 mol%. This suggests that the different compositions should be operated over different temperature ranges for maximum thermal to electrical energy conversion. The energy and power densities generated by the Olsen cycle using x/65/35 PLZT samples were measured by successively dipping the samples in isothermal dielectric oil baths. Large energy and power densities were obtained when the samples underwent the ergodic relaxor–ferroelectric phase transition. A maximum energy density of 1014 J l−1 per cycle was obtained with a 190 μm thick 7/65/35 PLZT sample cycled at 0.026 Hz between 30 and 200 °C and between 0.2 and 7.0 MV m−1. To the best of our knowledge, this is the largest pyroelectric energy density ever demonstrated experimentally with ceramics, single crystals, or polymers. A maximum power density of 48 W l−1 was achieved using a 200 μm thick 6/65/35 PLZT sample for temperatures between 40 and 210 °C and electric fields between 0 and 8.5 MV m−1 at a frequency of 0.060 Hz. The maximum applied electric field and temperature swings of these materials were physically limited by dielectric breakdown and thermomechanical stress.

Pyroelectric and Electrocaloric Properties of PZT- and BT-Based Ceramics

Thermal energy harvesting using non-linear pyroelectric effects in PZT with different Tc, PLZT, Ba(Zr0.2Ti0.8)O3 and (Ba0.8Sr0.2)TiO3 ceramics, and PMN-PT crystals were investigated. PLZT ceramics with Tc of 140°C exhibited large energy generation of 54.8 J/L/cycle with temperature variations from 30°C to 200°C and field variations from 0 to 20 kV/cm. Ba(Zr0.2Ti0.8)O3 ceramics with Tc of 40°C exhibited energy generation of 58.6 J/L/cycle with temperature variations from 30°C to 125°C and field variations from 0 to 20 kV/cm. The electrocaloric temperature changes ΔT due to applied ΔE were measured. PLZT(7/65/35) ceramics exhibited ΔT of 0.2 K at room temperature under a bipolar switching field of 20 kV/cm.

Effect of Soaking Time on Phase Formation and Electrical Properties of PLZT Based Ceramics

Lead lanthanum zirconate titanate ceramics (PLZT) are well known for their excellent dielectric, piezoelectric and ferroelectric properties and electro-optic characteristics. The solid solutions of compounds are expected to possess very interesting properties, making them promising candidates for electromechanical devices. This study describes processing and sintering conditions and electrical properties of the PLZT ceramics (9/65/35) that were successfully prepared from the respective starting materials by vibro-milling mixed-oxide method at various soaking time conditions for optimized properties. A composition and microstructure of the ceramics were investigated using X-ray diffraction and scanning electron microscopy. The dielectric properties of the densified samples were examined as a function of temperature and frequency to verify the relationships between soaking time conditions, phase formation, densification, microstructural development, dielectric, and ferroelectric characteristics.

Magnetic and Piezoelectric Properties of the Fe<sup>3+</sup> Doped PLZT Electroceramics

For the growing interest in developing of more attractive multiferroic and magnetoelectric ceramics an alternative is a double-doped Pb(Zr1-xTix)O3- material with trivalent lanthanum and iron ions. Such material has a structure based on ABO3 perovskite and properties depending on the chemical and structural composition. In the present work the results of the preparation and characterization of Fe3+- modified 9/65/35 PLZT ceramics have been reported. Two samples of Pb0,91(La1-zFez)0,09(Zr0,65Ti0,35)0,9775O3 ceramics, for different Fe ions concentration (z = 0,0 and 0,5 at.%), were prepared from the MOM derived powders and sintered by the hot uniaxial pressing methods. To analyze the obtained ceramics properties the XRD, SEM and also application oriented dielectric and magnetic measurements were performed. The Fe3+ substitution at the La-site of PLZT has shown many interesting and unusual dielectric, piezoelectric and magnetic properties. The obtained material was proposed to implement into Piezoelectric Transformer structure to change gain characteristics proportionally to magnetic field intensity.

Direct thermal to electrical energy conversion using 9.5/65/35 PLZT ceramics in the ergodic relaxor phase

This paper reports on direct thermal to electrical energy conversion by performing the Olsen cycle on 9.5/65/35 lead lanthanum zirconate titanate (PLZT). The Olsen cycle consists of two isothermal and two isoelectric field processes in the electric displacement versus electric field diagram. It was performed by alternatively dipping the material in hot and cold dielectric fluid baths under specified electric fields. The effects of applied electric field, sample thickness, electrode material, operating temperature, and cycle frequency on the energy and power densities were investigated. A maximum energy density of 637 ± 20 J/L/cycle was achieved at 0.054 Hz with a 250-μm-thick sample featuring Pt electrodes and coated with a silicone conformal coating. The operating temperatures varied between 3°C and 140°C and the electric field was cycled between 0.2 and 6.0 MV/m. A maximum power density of 55 ± 8 W/L was obtained at 0.125 Hz under the same operating temperatures and electric fields. The dielectric strength of the material, and therefore the energy and power densities generated, increased when the sample thickness decreased from 500 to 250 μm. Furthermore, the electrode material was found to have no significant effect on the energy and power densities for samples subject to the same operating temperatures and electric fields. However, samples with electrode material possessing thermal expansion coefficients similar to that of PLZT were capable of withstanding larger temperature swings. Finally, a fatigue test showed that the power generation gradually degraded when the sample was subject to repeated thermoelectrical loading.

Electrically induced light scattering performances of lanthanum-modified lead zirconate titanate transparent ceramics

A series of lanthanum-modified lead zirconate titanate (PLZT) ceramics of Zr/Ti (70/30) with different La concentration (La = 7.6, 7.8, 8.0 mole %) were prepared by a hot pressing process. The performances of electrically induced light scattering for PLZT (X/70/30) ceramics were investigated and analyzed systematically. All samples are crystallized into a single perovskite phase. The PLZT (7.6/70/30) sample exhibits a ferroelectric behavior while both PLZT (7.8/70/30) and PLZT (8.0/70/30) samples show an antiferroelectric behavior. The phase transition temperature (Tc) of the PLZT (X/70/30) ceramics shifts slightly from ~86 °C to ~89 °C with the increasing of La concentration at 1 kHz. All three ceramic samples exhibit a high transmittance, i.e., greater than 60 %, with a thickness of 0.4 mm over a wide range of wavelength band, from visible to near IR. The PLZT (X/70/30) ceramics exhibit three different types of light scattering behavior depending on the La concentration (examined at λ = 632.8 nm). Among them, PLZT (8.0/70/30) presents a unique applicable auto-switchable property with a low threshold value of electric field and high transmittance. Noticeably, the contrast ratio increases correspondingly with the thickness of the sample, and the contrast ratio aroused by the transverse electric field is about twice as big as that aroused by the longitudinal one. The light scattering properties of the PLZT (8.0/70/30) ceramic may represent a creative application in optical modulators.

Iodine photodissociation laser with an intracavity space — time light modulator

A scheme of an iodine laser with two different intracavity space — time modulators based on electrooptic PLZT ceramics is experimentally studied. It is shown that lasing can occur in differentangular directions with the use of both modulators. The output laser energy is 10 mJ with a pulse duration of 200 μs and a beam divergence of 6.3 × 10-4 rad. The laser field of view (5.1 × 10-3 rad) consists of a discrete set of 8 × 8 directions.

Mechanically activated PLZT ceramics: Structural and electrical properties

Ultrafine powders of (Pb0.92La0.08) (Zr0.60Ti0.40)O3 (hereinafter designated as PLZT) have been synthesized from oxide powders using the high energy ball milling technique in air atmosphere. The powders milled in agate vials using Yttria stabilized Zirconia (YTZ) balls, were all about 20nm in size. XRD revealed the formation of a significant amount of the perovskite PLZT phase at room temperature itself. The bulk ceramic samples were subjected to electrical poling, prior to performing resonance measurements on them, in order to determine the piezoelectric and electromechanical coupling coefficients. Poled samples exhibited large strains under the influence of applied electric fields, with limited hysteresis. The effect of powder refinement on the structural and electrical properties of PLZT ceramics are correlated in this paper.

Excellent electrostrictive properties of low temperature sintered PZT ceramics with high concentration LiBiO2 sintering aid

The effect of LiBiO2 (LBO) additive on the sintering of Pb0.97La0.03(Zr0.53Ti0.47)0.9925O3 (PLZT) ceramics was carefully investigated. 6.0wt% LBO added PLZT powders could be fully densified to 98% relative density at a temperature as low as 950°C. It is worthy to notice that there are distinct enhancements in piezoelectric and electrostrictive properties by increasing the soaking time from 2h to 7h, which could mainly originate from the improvement of crystallinity and grain size of PLZT ceramics. By controlling the soaking time and concentration of LBO addition, PLZT ceramics sintered at 950°C could exhibit high curie temperature of 240°C and very high S11 of 0.22% under 3.0kV/mm, which is even better than that of traditionally sintered PZT-5, PMN–PZT, and this is very promising for actuators designed in multilayer structure in high temperature environment.

Light Scattering Properties for PLZT Transparent Ceramics of Different Zr/Ti Ratios

Lead lanthanum zirconate titanate (PLZT) transparent ceramics present an attractive electrically controlled light scattering performance with high transmittance and large contrast ratio. PLZT ceramics of 8 mole% lanthanum with different Zr/Ti ratios (Zr/Ti=68/32, 70/30, 72/28) were prepared by the hot pressing method to figure out the influence of Zr/Ti ratios to the light scattering performance. X-ray diffraction patterns confirm that all the samples are perovskite structure with no secondary impurity phase detected. All the three compositions show double tending slim hysteresis loops which due to antiferroelectric phase coexisted. Besides, within the range of near-infrared to ultraviolet wavelength, all the PLZT samples show high transmittance. While the Zr/Ti ratio increasing from 68/32 to 72/28, the transmittance reduced value RT of the sample decreases gradually (λ: 632.8 nm). PLZT (8/68/32) sample shows a maximum RT, it promises a good application in optical modulators, goggles and so on.

Study of the Anelastic Behavior of PZT and PLZT Ferroelectric Ceramics

The anelastic behavior of the ferroelectric ceramics (Pb)(Zr/Ti)O3(PZT) and (Pb/La)(Zr/Ti)O3(PLZT), with Zr/Ti = 65/35, La = 5 at.% and 8 at.%, was investigated in the region of the ferroelectric phase transitions. Anelastic spectroscopy experiments were performed in an acoustic elastometer system, operating in a kilohertz bandwidth, at temperatures rising from 300 K to 770 K, at a heating rate of 1 K/min, under pressure of 10-5mbar. Anelastic measurements on PZT showed only one anomaly, associated with the occurrence of a ferroelectric-paraelectric phase transition, while the PLZT data showed two anomalies, which were associated with the following transitions: the ferroelectric-paraelectric phase transition and a ferro-ferroelectric phase transition between distinct rhombohedral ferroelectric phases. The behavior of the relative variation of the elastic moduli with temperature, near the phase transitions, which describes the change in the type of coupling between strain and the order parameter in ferroelectric-paraelectric phase transition, with the increase of lanthanum amount and, linear coupling in the strain and order parameter type to PZT ceramic and linear coupling in the strain but quadratic in order parameter type for PLZT ceramics.

High Resolution EBSD/SEM Analysis of PLZT Ferroelectric Crystals in Low Vacuum Conditions - A few Practical Remarks

Modern scanning electron microscopes (SEMs) increase the ability to study a wide range of materials. Especially, an application of low vacuum conditions enables characterization of nonconductive samples without complicated preparation procedure. However, the operator must be aware of several problems he may encounter collecting electron diffractions in the SEM with variable pressure. The charge control and quality of the surface are the challenges when running experiments on insulators. Specimen charging obscures forward scatter electrons images and decreases the EBSD pattern quality making indexing difficult or even impossible. Another crucial question is how to limit the influence of so called "skirt effect" caused by ionization of gas molecules followed by electron beam broading above the sample. The influence of several important parameters (gas pressure, a type of gas, working distance and energy of electron beam) on the EBSD pattern quality must also be considered. When it is properly done, a coupling of crystallographic information with the chemical data obtained from Energy Dispersive Spectroscopy (EDS) in the LV-SEM allows to perform phase identification of insulators. The paper presents some ideas how to deal with the (Pb, La)(Zr, Ti)O3 ceramics in high resolution Quanta 3D SEM (with thermally assisted Schottky type FEG) equipped with EDAX-TSL system in low vacuum environment. The problems occurring during EBSD analysis of the PLZT ceramics are discussed and some solutions are suggested. Paper summarizes the results obtained from PLZT ferroelectric ceramics in the low vacuum FEGSEM and shows how to optimise experimental parameters in order to achieve the best quality of orientation maps acquired from nonconductive samples.

Influence of Mn-doping on phase transition characteristics and relaxor behaviour of lead lanthanum zirconate titanate ceramics

Changes in dielectric response features of lead lanthanum zirconate titanate (PLZT) ceramics by manganese addition are reported in the present work. Both the PLZT relaxor behaviour and the frequency dependence of the room temperature dielectric constant are shown to be suppressed by the addition of manganese. Similar results are obtained by applying a bias external field or by chemical reduction of PLZT samples, thus indicating the presence of an interrelationship between oxygen vacancies and the random ‘bias’ electric field. Consequently, the defects created by oxygen vacancies appear as the most important factor causing the disappearance of relaxor behaviour in Mn-doped PLZT ceramics. No modifications in the diffuse phase transition with the manganese content are found, which may be due to the persistence of compositional disorder. Additionally, it was verified that the spin glass model cannot be used to describe these observed effects.