Papers by Keyword: PLZT

Abstract: The sol-gel process was employed to prepare (Pb_1-xLa_x)(Zr_1-yTi_y)O₃ (PLZT) ceramics with nominal composition Pb_0.93La_0.07(Zr_0.57Ti_0.43)_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.

Abstract: 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.

Abstract: 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 R_T of the sample decreases gradually (λ: 632.8 nm). PLZT (8/68/32) sample shows a maximum R_T, it promises a good application in optical modulators, goggles and so on.

Abstract: 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.

Abstract: (100)-oriented PLZT ((Pb_1-x, La_x) (Zr_y,Ti_1-y)_1-x/4O₃, x/y=9/65) films of up to ~ 1.23 μm have been developed on LaAlO₃ single crystal substrate by magnetron sputtering. The as-grown PLZT thin films exhibit high optical transparency in visible and near-infrared light wavelength and high quadratic (Kerr) EO coefficients. Prism coupler measurements reveal that the PLZT thin films possess large refractive index, as high as 2.524 in TE model and 2.481 in TM model. The transparency of >70% in the range of λ= 500-1200 nm, the optic band gap of 3.42 eV and the quadratic electro-optic (EO) coefficient of 3.38 x 10^-17 (m/V)² have been measured in the films. Due to the large EO coefficient and the micrometric thickness, the as-developed PLZT films have great potential in developing longitudinal-or transverse-type EO devices in electric and optic field

Abstract: Effect of La2O3 addition on microstructure, morphology and pressure sensing behaviour of (Pb1-x, Lax)(Zr0.52, Ti0.48)O3 based ceramics was studied in three different compositions of La2O3, namely x = 0.10, 0.12 and 0.15. The samples were prepared through a conventional solid-state reaction method using high purity metal oxides powders. In order to control the PbO losses due to high sintering temperature, a novel approach was explored whereby the samples were sintered in Al2O3 environment. Structural investigation using XRD revealed that all samples exhibited a tetragonal crystal structure. However the c/a ratios exhibited a decreasing trend as the La2O3 content increased, indicating that (Pb1-x, Lax)(Zr0.52, Ti0.48)O3 crystals gradually evolved towards pseudocubic structure. SEM micrographs showed that in all samples the grains have uniform pebble stone morphology. The average grain size reduced from ~ 4.5 µm to ~ 3.0 µm with the increment of La¬2O3 content. The performance of pressure sensing behaviour which was investigated using custom-made pressure chamber showed that sample with composition of x = 0.10 exhibited the best piezoelectric properties with high pressure sensitivity, good stability and repeatability.

Abstract: To prevent the potential cracking of gel fibers, La modified lead zirconate titanate (PLZT) ceramic fibers with diameter within 50µm were achieved by embedding into PLZT powders during the heat treatment. Then the 1-3 PLZT fiber/interpenetrating polymer network (IPN) piezoelectric composites were prepared by casting the IPN precursors onto the well aligned ceramic fibers. The influences of the heating temperatures and La amounts on the dielectric constant, dielectric loss with frequencies and piezoelectric constant of PLZT were investigated in detail. The morphologies of fibers and composites were observed by biological microscope. And also, the dielectric constant of PLZT fibers and PLZT fiber/IPN piezoelectric composites were detected.

Abstract: High-resolution Brillouin scattering technique was applied to study the dynamics of central peaks (CPs) in two relaxor ferroelectric systems, PLZT-x/65/35 ceramics and PMN-33%PT [001] single crystals, respectively. It was found that CPs appear very close to an intermediate temperature, Td, for both type of specimens. The temperature dependence of CPs was attributed to the appearance and subsequent growth of polar nanoregions (PNRs) intrinsic to relaxor materials.

Abstract: PLZT9/65/35 thick films were prepared from the solution containing PVP360 (polyvinylpyrrolidone, with average molecular weight of 360000). With the solutions, the critical thickness of a single PLZT layer could increase to ~624nm compared with 77nm-thick films prepared without PVP360. Furthermore, by adding 20~35% excess of Pb to the precursor solutions, the nano-porous rosette-like structures and a small amount of pyrochlore remnant, which were found very common in the PVP-modified films, could be eliminated. 35% Pb excess was also found to initiate liquid-phase sintering, leading to dense and crack-free films. The effect of Pb excess on the rosette removal and densification behavior of the films was discussed. Moreover, the optical and electrical properties of the PLZT films with 35% Pb excess were also studied.

Abstract: Lanthanum-modified lead zirconate titanate and lead zirconate titanate epitaxial films with (100) and (111) orientations were grown respectively on (100) and (111) niobium, lending conductivity to strontium titanate through chemical solution deposition. This study investigated changes in the ordinary and extraordinary refractive index
no and
ne induced in these films by an electric field using the prism-coupling method. In the (100) epitaxial PZT 30/70 film, anisotropic electro-optic effects arise from the Pockels effect. The isotropic electro-optic effect, which is
no =
ne , was achieved on (100) epitaxial PLZT 8/65/35 and PZT 70/30 films.