PLZT Samples Research Articles

Structural quantification of polar/nonpolar phases of relaxor clusters in transparent ferroelectric ceramics

A dual-phase refinement protocol considering distinct amounts of polar/nonpolar phases reflecting the polar nano phases formation in two relaxor ferroelectric systems was performed. The samples of PLZT and PLMN-PT have shown a typical relaxor behavior with different freezing temperatures, and the amounts of the polar phase of the lack of ergodicity were obtained using structure parameters.

Figures of merit of PLZT ferroelectric ceramics for practical applications

Structural, microstructural and pyroelectric properties were investigated in PZT-based ferroelectric ceramics for a composition close to the morphotropic phase boundary (Zr/Ti = 53/47), as a function of the lanthanum content. The samples were prepared via the conventional solid-state reaction sintering method. Three compositions were synthetized and studied following the PbZr0.53Ti0.47O3 + x mole% La nominal formula, where x = 0.0, 2.5 and 5.0. The structural characterization confirmed the presence of both tetragonal and rhombohedral phases for all the studied compositions, showing a decrease in the tetragonality factor (c/a) with the increase of the lanthanum concentration. The observed decrease in the stability of the ferroelectric phase (in favor of the paraelectric one) have been discussed in light of the solubility of the doping cation into the studied PZT perovskite structure. Microstructural properties revealed low pores concentration micrographs, showing homogeneous microstructures and uniform grain-sizes. The pyroelectric response of the as-prepared PLZT samples was also investigated in a wide temperature interval. The lower lanthanum content composition exhibited the best properties, characterized by a high pyroelectric coefficient and enhanced figures of merit. These characteristics make such a composition a promising material for practical applications.

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.

Electrocaloric and electromechanical properties of (Pb,La)(Zr,Ti)O3 ceramics

The direct observation of temperature changes in (Pb,La)(Zr,Ti)O3 (PLZT) (4/90/10), (8/80/20), and (8/70/30) ceramics during cycle of applying and removing electric field were utilized to evaluate their electrocaloric effects. The temperature change under the electric field drew temperature-electric field (T-E) hysteresis loops peculiar to each material. PLZT(4/90/10) ceramics exhibited a double hysteresis peculiar to antiferroelectrics in polarization-electric field (P-E) loops. A temperature drop of −0.07 K due to the application of an electric field of 70 kV/cm was observed directly by measuring the T-E loop. This temperature drop is due to a negative electrocaloric effect. PLZT(8/80/20) and (8/70/30) ceramics exhibited slim P-E loops with constriction and typical ferroelectric loops, respectively. The temperature changes induced by a bipolar switching field of 40 kV/cm in the PLZT(8/80/20) and PLZT(8/70/30) ceramics were both positive 0.22 K. The measured T-E loops had shapes similar to those of the strain-electric field loops in samples of PLZT(8/80/20) and PLZT(8/70/30) ceramics. PLZT(8/80/20) ceramics exhibited their largest electromechanical properties at around 25 °C, and the properties then decreased with increasing temperature.

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.

Effect of composition and grain size on dielectric, ferroelectric and induced strain behavior of PLZT/ZrO2 composites

Lead lanthanum zirconate titanate ceramics (PLZT) are well known for their excellent dielectric, piezoelectric and ferroelectric properties. In this study, PLZT 9/70/30, 9/65/35 and 9/60/40 ceramics were prepared by vibro-milling mixed-oxide method. All compositions of powders were uniaxial pressed in pellets and sintered at the temperatures of 1200–1275°C with various soaking times of 2, 4 and 6h. The X-ray diffraction (XRD) patterns confirmed that all the PLZT samples had perovskite structure with ZrO2 as a second phase and PLZT/ZrO2 composite structure was formed. Dielectric behavior at the frequency of 1kHz showed broad peak indicating relaxor ferroelectric behavior and the difference of the temperature at maximum dielectric at different frequencies increased when Zr:Ti ratio increased. Polarization with electric field (P-E loop) at room temperature showed that when Zr:Ti ratio increased, the coercive field decreased resulting from crystal structure change from tetragonal to rhombohedral. Induced strain with electric field depended on microstructure where the value of Smax/Emax tended to decrease with increasing grain size. It can be concluded that dielectric and ferroelectric behavior predominantly depended on composition of PLZT ceramics and induced strain behavior predominantly depended on grain size of PLZT ceramics.

Effects of Zr/Ti Ratio on the Electric-Induced Light Scattering Performances of PLZT Transparent Ceramics

Lead lanthanum zirconate titanate (PLZT) transparent ceramics have attracted more and more attentions for their unique electric-induced light scattering effects. The PLZT ceramics of 7.45 mole% lanthanum with different Zr/Ti ratios (Zr/Ti=68/32, 69/31, 70/30, 71/29, 72/28) were prepared by the hot-press sintering method. The X-ray diffraction patterns confirm that all the PLZT samples are perovskite structure without detected secondary phases. The SEM images of the fracture surfaces of the samples show that all the PLZT materials tend to fracture transgranularly, and exhibit fully dense and uniform microstructures. All the samples with different Zr/Ti ratios present typical relaxation ferroelectric phase transition characteristics with square shaped hysteresis loops. Noticeably, all the original PLZT samples show an excellent transparency in the wavelength range from visible to near-infrared, and they will become opaque after an appropriate electric field experienced. The opaque sample can also recover to the transparent state when an inverse compatible electric field acts on it. The contrast ratio of the sample increases firstly and then decreases when the Zr/Ti ratio increases from 68/32 to 72/28 (λ=632.8nm). The PLZT (7.45/70/30) material shows a maximum contrast ratio, which makes it promising to apply in optical modulators.

Refining the phase diagram of Pb1−xLax(Zr0.9Ti0.1)1−x/4O3 ceramics by structural, dielectric, and anelastic spectroscopy investigations

We present the results of dielectric and anelastic spectroscopy measurements, together with X-ray diffraction investigations, which allow us to establish more precisely the phase diagram of Pb1−xLax(Zr0.9Ti0.1)1−x/4O3 (PLZT x/90/10) in the compositional range around the AFE/FE phase boundary (0 < x < 0.04). From structural analysis and polarization-electric field measurements, we have found that the ground state of PLZT samples with x < 0.025 is rhombohedral R3c, while samples with x > 0.032 are antiferroelectric with orthorhombic Pbam structure. In-between, for compositions with 0.025 ≤ x ≤ 0.032, a coexistence of the AFE/FE phases is evidenced. The use of complementary dielectric and anelastic techniques allows to follow the phase transitions shifts throughout all the interesting composition range and to construct the temperature-composition phase diagram. The tilt instability line, separating the R3c and R3m low and high temperature phases, has been evidenced. Moreover, the new transition, associated with the onset of disordered tilting preceding the long range order of the R3c phase, previously found in Zr-rich Pb(Zr,Ti)O3, is confirmed in rhombohedral PLZT x/90/10 compositions.

Direct ink writing of 3–3 piezoelectric composite

Three dimensional (3D) ceramic structures form a construction of piezoelectric composite would be prepared with direct ink writing method (DIW). The preparation of aqueous based lead zirconate titanate lanthanum (PLZT) inks and the principle of DIW were systematically investigated. The ink with solids volume fraction about 70vol% by aging 48h reveals shear-thinning behavior and proper viscoelastic properties. As shown by scanning electron microscopy (SEM), PLZT samples sintered at 1200°C for 4h in a lead-rich atmosphere yielded best microstructures which were densified with relative density exceed 98%. The test of X-ray diffraction (XRD) reveals that the main phase of sintered samples is rhombohedral Pb0.93La0.07(Zr0.65Ti0.35)0.9825O3. 3–3 Piezoelectric composite formed by 3D PLZT ceramics filled with epoxy resin at 40°C have higher hydrostatic figure of merit dhgh (4112×10−15m2/N) than that of the monolithic PLZT piezoelectric ceramics (365×10−15m2/N). Piezoelectric ceramic–polymer composites can be widely used for the applications like underwater acoustic transducers in having combined hardness and electric properties of piezoelectric ceramics and flexibility, low density and low acoustic impedance of polymers.

Temperature Dependence of Electric‐induced Light Scattering Performance for PLZT Ceramics

PLZT (7.45/71/29) ceramics with fully dense microstructure and high transmittance were fabricated by a hot‐press sintering method. The effects of temperature on the phase structure, ferroelectric property, and electric‐induced light scattering performance of the PLZT ceramics were examined and analyzed. XRD patterns indicated that the PLZT sample tended to transform from rhombohedral phase to tetragonal phase with the temperature increasing. And the temperature‐dependent ferroelectric hysteresis behavior of the PLZT sample revealed the conversion of a saturated square hysteresis loop to a double‐loop‐like hysteresis loop, accompanied with the significant reduction in coercive field and remnant polarization. Depending on the temperature, the PLZT sample exhibited three different kinds of electric‐induced light scattering performance.

Lanthanum Dependence of the Electrically Controlled Light Scattering Performances of PLZT Transparent Ceramics

Lead lanthanum zirconate titanate (PLZT) transparent ceramics have attracted more and more attentions for their unique electrically controlled light scattering effects. By the hot-press sintering method, a series of PLZT (X/70/30) ceramics with different La concentration (7.3, 7.4, 7.45, 7.5, 7.6 mole %) have been synthesized to figure out its influence on the electrically controlled light scattering performances. XRD patterns reveal the formation of a single-phase perovskite structure for all samples. The PLZT (7.3/70/30, 7.4/70/30, 7.45/70/30) samples exhibit a ferroelectric behavior, but with the La concentration increasing, the samples exhibit a tendency of a double hysteresis loop which is due to antiferroelectric phase coexisted. The temperature of maximum dielectric constant (Tm) of the PLZT (X/70/30) ceramics shifts from ~99 °C to ~87 °C with the increasing of La concentration at 1 kHz. All samples exhibit a high transmittance (61%, 0.35 mm) within the wavelength range from visible to near-infrared light. Depending on the La concentration, the light scattering behavior of PLZT ceramics exhibit two main types, in which PLZT (7.45/70/30) promises a unique potential application in laser modulators for its outstanding advantages of less energy consumption and relatively larger contrast ratio.

Local order of Pb1−xLaxZr0.40Ti0.60O3 ferroelectric ceramic materials probed by X-ray absorption and Raman spectroscopies

Abstract This paper reports on the structural characterization of Pb 1− x La x Zr 0.40 Ti 0.60 O 3 (PLZT) ferroelectric ceramic compositions prepared by the conventional solid state reaction method. X-ray absorption spectroscopy (XAS) and Raman spectroscopy were used to probe the local structure of PLZT samples that exhibits a normal and relaxor ferroelectric behavior. From the Zr K-edge and Pb L III -edge EXAFS spectra, a considerable dissymmetry of Zr and Pb sites was observed in all samples, including those showing a long-range order cubic symmetry and a relaxor behavior. The Raman spectroscopy results confirmed the existence of a local disorder in all PLZT samples through the observation of Raman active vibrational modes. The variation in the intensity of the E (TO 3 ) mode in the PLZT relaxor samples indicates that the process of correlation between nanodomains stabilizes at temperatures lower than T m .

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.

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.

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.

Direct Write Assembly of 3-Dimensional Structures with Aqueous-Based Piezoelectric Inks

A kind of aqueous based suspensions of lead lanthanum zirconnate titanate (PLZT) was developed for direct ink writing (DIW) assembly. Piezoelectric ceramic woodpile structures with diameter of 315-470μm were fabricated from these inks by using DIW. The preparation of aqueous based piezoelectric inks, the principle of DIW and the sintering process were systematically discussed. The ink with solids volume fraction over 70% by 1 day aging reveals shear-thinning behavior and proper viscoelastic properties, which ensures a feasible extrusion in the whole shaping process. The PLZT samples sintered at varying temperatures between 1150 oC and 1250 oC for 2h or 4 h in either air or a lead-rich atmosphere yielded various microstructures observed by scanning electron microscopy (SEM). Choosing the optimum sintering condition, the sintered products were densified with relative density exceed 98%. The test of X-ray diffraction (XRD) analysis reveals that the main phase of sintered samples is rhombohedral Pb0.93La0.07(Zr0.65Ti0.35)0.9825O3. The direct ink writing technique has advantages of good design ability and rapid forming capability, which opens up a potential route for the design and fabrication of piezoelectric devices.

Pyroelectric waste heat energy harvesting using relaxor ferroelectric 8/65/35 PLZT and the Olsen cycle

Waste heat can be directly converted into electrical energy by performing the Olsen cycle on pyroelectric materials. The Olsen cycle consists of two isothermal and two isoelectric field processes in the electric displacement versus electric field diagram. This paper reports on the electrical energy generated by lanthanum-doped lead zirconate titanate (8/65/35 PLZT) subjected to the Olsen cycle. The material was alternately dipped into a cold and a hot silicone oil bath under specified electric fields. A maximum energy density of 888 J l−1/cycle was obtained with a 290 µm thick 8/65/35 PLZT sample for temperatures between 25 and 160 °C and electric fields cycled between 0.2 and 7.5 MV m−1. To the best of our knowledge, this is the largest pyroelectric energy density experimentally measured with multiple cycles. It corresponded to a power density of 15.8 W l−1. The electrical breakdown strength and therefore the energy and power densities of the material increased as the sample thickness was reduced from 720 to 290 µm. Furthermore, a physical model for estimating the energy harvested by ferroelectric relaxors was further validated against experimental data for a wide range of electric fields and temperatures.

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.

Effects of lanthanum modification on electrical and dielectric properties of Pb(Zr 0.70,Ti 0.30)O 3 ceramics

Lanthanum modified lead zirconate titanate ceramics with lanthanum content changing from 7.6 to 9.0 at.% La and a Zr/Ti ratio of 70/30 (PLZT 100x/70/30) have been prepared by conventional high temperature solid-state reaction technique. The studies of the ferroelectric, electromechanical and dielectric properties of the ceramics were carried out. The results showed the enhanced antiferroelectricity stability when the lanthanum content increases. The polarization and strain decreased with the increasing La content. The dielectric spectra of all the PLZT samples show a dispersive behavior. With increasing La concentration, the maximum dielectric constants ε m and the transition temperatures T m were reduced.

Electron Emission from Ferroelectric Cathodes Stimulated by Repetition Frequency High-Voltage Pulse

Stable electron emission from ferroelectric cathodes made of lead zirconate-titanate Lanthanum doped (PLZT) ferroelectric ceramic stimulated by high-voltage pulses with a repetition rate of 80 Hz is obtained. The emission properties and lifetime are studied. To excite electron emission and obtain bigger current, a positive driving pulse is applied to the rear electrode of the cathodes, and an extracting voltage is applied to the graphite anode. The image and the structure of the emitting surface and broken side of the samples tested for electron emission before and after are studied by photographs and scanning electron microscopy. It is found that a substantial damage presenting in the tested cathodes. According to the experimental results, some possible interpretations are given for the damage of PLZT samples.