Sol-solvothermal synthesis and characterization of fine lead zirconate titanate particles

We present a novel low-temperature sol-solvothermal method to synthesize fine lead zirconate titanate (PZT) particles. This sol-solvothermal method combines the advantages of conventional sol–gel process and the solvothermal method, and isopropyl alcohol (IPA) was used as the solvent. The effects of different parameters including KOH concentration, IPA/(IPA + water) ratio and reaction temperature, on the microstructures of the PZT powder were studied. With increasing KOH concentration and reaction temperature, the crystalline structure of as-synthesized PZT transformed from tetragonal to rhombohedral phase. More IPA added in the solvent can effectively reduce agglomeration of the PZT powder and decrease the crystallization temperature, but impurity phase was also detected at high IPA/(IPA + water) ratio. As a result, the synthesis parameters are optimized, and well-crystallized 700 nm PZT particles were successfully synthesized in 2.0 M KOH and 50 % IPA/(IPA + water) ratio at temperatures as low as 120 °C.     

Dip-coating conditions and modifications of lead titanate and lead zirconate titanate films

The modifications of dip-coated lead titanate (PT) and lead zirconate titanate (PZT) films strongly depend on the film thickness and the substrate in addition to the heat-treatment temperature. At 500 to 600 ° C, metastable paraelectric pyrochlore grew on glass plates (amorphous plates) when the thickness of the coated films produced by one coating cycle was below 100 nm, while ferroelectric perovskite formed on crystalline substrates or when thick films were coated on amorphous plates. This tendency is discussed in terms of an inhomogeneous reaction and the epitaxial effect. The perovskite PT films coated on single-crystal SrTiO₃ plate at 700 ° C were strongly oriented to thec-axis.     

Electrodeposition of lead zirconate titanate nanotubes

Lead zirconate titanate (PZT) nanotubes have been grown using porous anodic alumina templates. Sol–gel electrophoretic deposition method was utilized to form the nanotubes on pore walls. The templates were prepared using various anodizing voltages to achieve different pore diameters. Phosphoric acid solution was employed as the electrolyte. Stabilized PZT sols were prepared using lead acetate trihydrate and modified precursors of zirconium and titanium with acetic acid. The filled templates were then sintered at 700 °C. Scanning electron microscopy (SEM) shows that tubular PZT arrays have been efficiently grown in the alumina templates. Transmission electron microscopy (TEM) further confirms the tubular form and polycrystalline nature of the tubes. Energy dispersive X-ray (EDX) analyses also confirm the composition of the tubes. X-ray diffraction (XRD) spectra indicate the presence of the perovskite PZT as the main phase.     

Electrohydrodynamic deposition of nanostructured lead zirconate titanate

The deposition of a propanol-based lead zirconate titanate (PZT) sol using electrohydrodynamic atomization (EHDA) in the stable cone-jet mode was investigated. The droplets generated were deposited onto a copper substrate as a film, which was investigated using X-ray diffraction and scanning electron microscopy. The PZT film was shown to contain uniform nano-particles of PZT, which maintained their shape on sintering (650 degrees C, 1 hour) while forming the perovskite phase of PZT.     

Water based gelcasting of lead zirconate titanate

Gelcasting is a novel forming method for making high-quality ceramic parts by means of in situ polymerization where only a few percents of a polymerizable binder are needed. In this article the viscosities of lead zirconate titanate (PZT) suspensions with 15-52 vol.% solids loading were studied. After developing a concentrated PZT suspension with a low viscosity, gelcasting was successfully used to form PZT ceramic parts. Microstructures and piezoelectric properties of gelcast samples derived from suspensions with different solids loading were also investigated in comparison with those of die pressed ones. It was found that gelcast samples exhibited slightly stronger piezoelectric effect than the die pressed ones at the same sintering procedure. Based on the comparison of the density and pore structure results of the samples prepared by these two methods, their different piezoelectricity may be attributed to their microstructure difference.     

Micropore formation in lead zirconate titanate films

This paper presents an experimental study of the pyrochlore-to-perovskite phase transition in ferroelectric lead zirconate titanate (PZT) films grown on silicon substrates by rf magnetron sputtering and annealed in air or in an inert (argon) atmosphere at temperatures of up to 600°C and atmospheric pressure. Simultaneous thermal analysis results demonstrate that annealing in air leads to release of the latent heat of the phase transition, which is due to the conversion of lead oxide to lead orthoplumbate in the bulk of the PZT film. This transition is accompanied by changes in the densities of the perovskite phase and parent (pyrochlore) phase. In this case, the possibility of phase transformation should be ensured by changes in the volume of the system. The change in the volume of the film leads to the formation of micropores in the bulk of thin PZT films. The micropore size has been determined by scanning electron microscopy, and the phase composition of the films has been assessed by X-ray diffraction. We present experimental evidence that micropore nucleation and growth at the interface between the new and old phases in thin PZT films is due to the difference in density between these phases.     

Colloidal processing of lead lanthanum zirconate titanate ceramics

Well-dispersed aqueous slurries of fine ceramic powders with high solids loading are often required for various shape forming techniques such as slip and tape casting in order to fabricate advanced ceramics with a dense and uniform microstructure. Colloidal processing of lead lanthanum zirconate titanate (PLZT) powders was conducted at various pH using ammonium polymethacrylate as a dispersant. Suspensions were characterized by viscosity and zeta-potential measurements. The effect of pH on polymer adsorption and the rheological behavior of the slurries were investigated and stabilization mechanisms discussed. Through optimization of the dispersant concentration and pH, solids loadings of the suspensions up to 50 vol.% with a relatively low viscosity were obtained.     

Characterization and microstructure of porous lead zirconate titanate ceramics

Porous lead zirconate titanate (PZT) ceramics are widely used because of their low acoustic impedance, high figure of merit and high hydrostatic sensitivity. In the present work, porous PZT ceramics were fabricated by incorporating polyethylene oxide (PEO) as pore-forming agent. Both PZT powder and PEO were mixed with a binder at different ratios and compaction was carried out. The samples were slowly heated to remove the pore-forming agent and binder without cracks, followed by controlled sintering and electrode forming. Samples were poled using corona poling technique. The ferroelectric properties and microstructure of the prepared ceramics were characterized. The correlation of porosity with microstructure and ferroelectric properties were discussed.     

不锈钢衬底上锆钛酸铅膜的制备

以改性二氧化锆为过渡层,用溶胶－凝胶法在不锈钢衬底上成功制备了锆钛比为52／48的锆钛酸铅膜,扫描电镜分析表明,膜的表面平整,无裂纹,X射线分析结果说明,经650℃退火30min后,膜为纯的钙钛矿相,以衬底为下电极、直径为0.32mm的金上电极,测量了0.8μm膜的电滞回线及其它性能,膜的剩余极化为18μC/cm^2。     

Hydrothermal synthesis of ferroelectric barium and strontium titanate extremely fine particles

BaTiO₃, SrTiO₃ and (Ba_{1– x}Sr_x)TiO₃ fine particles were synthesized from amorphous TiO₂ fine particles by a hydrothermal method. The relationship between the specific dielectric constant of the sintered disk and the mean size of composing particles has been investigated. The specific dielectric constants of the sintered disks of BaTiO₃ and SrTiO₃ particles attain values exceeding 6000 in the range of the particle size of 0.10–0.17 m. The specific dielectric constant for the sintered disk of (Ba_{1– x}Sr_x)TiO₃ particles synthesized at various atomic fractions of Sr (x) attains maximum values at both atomic fractions of 0.08 and 0.95. It has been suggested that the size of particles composing the disk should considerably affect the specific dielectric constant of the sintered disk.     

Reaction between lead zirconate titanate and yttrium iron garnet

High-temperature sintering of lead zirconate titanate (PZT) + yttrium iron garnet mixtures is accompanied by the formation of cubic yttria-stabilized zirconia. Quantitative phase analysis indicates that PZT loses at least 90% of the ZrO₂. This leads to appreciable changes in the composition of the constituent phases and has an adverse effect on the ME performance of the composite     

Piezoelectric and mechanical properties of ceria-doped lead zirconate titanate ceramics

Phases, microstructures and properties of lead-zirconate-titanate (PZT) ceramics with the compositions Pb(Zr_0.535– Ce Ti_0.465) O₃ where =0.0, 0.001, 0.01, 0.02 and 0.05 were studied. Rhombohedral and tetragonal phases were present at =0.0. The amount of the rhombohedral phase increased with increasing , and only the tetragonal phase was present for >0.001. Thec/a ratio of the tetragonal phase also increases with increasing . Particles of CeO₂ were found to be present in compositions with >0.01, indicating that the solubility of CeO₂ is less than 1a/o on the metals basis. The piezoelectric and electromechanical constants achieved maximum values for =0.001. The hardness increased monotonically with increasing . The modulus of rupture and the fracture toughness, however, went through a minimum and both stayed lower than their values for =0.     

Performance characteristics of smart-materials based on lead zirconate titanate

This paper deals with the characterization of smart-material combinations based on the principle of phase transformation; that may provide drastic change in resistance with a small change in pressure. Lead zirconate titanate (PZT) has been selected as a base material for the development of smart-material combinations and pressure-sensitive devices were fabricated using the same. The devices have been characterized with change in pressure. Both dynamic and static pressures were used for characterization of the devices. Fast switching action i.e. large change in resistance with pressure has been observed and discussed. The reliability tests on the devices have also been performed to establish their long-term stability.     

R-curve and subcritical crack growth in lead zirconate titanate ceramics

R-curves and subcritical crack growth curves (V–K_I) were determined for undoped, K doped (PKZT) and Nb doped (PNZT) lead zirconate titanate (PZT) ceramics and the results are discussed including the effect of doping, grain size and the polarisation state. A pronounced crack growth resistance was observed in the soft PNZT ceramic, which is attributed to ferroelastic domain switching. Subcritical crack growth in the studied PZT materials is governed by both environmentally stress-induced corrosion at the crack tip and the crack shielding due to domain switching. Increasing domain switching capacity by structural modification of the material (i.e. by donor doping or by increasing the grain size) or by poling sifts the V–K_I curve to higher values of the stress intensity factor.     

Hydrothermal synthesis of barium titanate fine particles from amorphous and crystalline titania

Barium titanate fine particles of cubic system were synthesized hydrothermally from aqueous barium hydroxide solutions with fine particles of either amorphous or crystalline (rutile) titania in suspension. The mean size of barium titanate particles prepared from amorphous titania ranged from 0.03 m to 0.11 m, depending on hydrothermal conditions. The particle size approximately agreed with the crystallite size (0.04–0.09 m). On the other hand, the mean size of barium titanate particles prepared from rutile titania ranged from 0.2 to 0.7 m, which was about six times as large as the crystallite size. The difference of sizes of barium titanate particles prepared might be ascribed to the difference in dissolution rates of amorphous or crystalline titania particles.Nomenclature mean particle size, m - BT barium to titanium molar ratio - d crystallite size, m - K shape factor appearing in Equation 3 - half value breadth of diffraction peak - lattice strain - Bragg diffraction angle, degree - wave length of X-ray, urn - _g geometric standard deviation defined by 84.1%-size/50%-size in a log normal size distribution     

Thermodynamic investigations of the solid solution of lead zirconate - lead titanate

The absolute and relative PbO-vapour pressures of PbTiO₃, PbZrO₂ and their solid solutions are determined at 1300, 923, 723 and 673 K by the dynamic thermobalance method and by EMF-measurements using PbF₂ and Ca-stabilized ZrO₂ as solid electrolytes. Thermodynamic formation data of PbTiO₃ and PbZrO₃ are obtained by extrapolation. The non-ideal behaviour of the solid solution can be successfully described by postulating an ordering equilibrium leading to Pb₄TiZr₃O₁₂ and requiring K = 0.30 (1300 K) [K = 0.02 (923 K)] as equilibrium constants.     

Thermally stimulated surface autosegregation in lead zirconate titanate ceramics

Thermally stimulated segregation on grain surfaces in lead zirconate titanate ceramics has been shown for the first time to be selective, as a result of which atoms occupying the same crystallographic position accumulate in the surface layer in a ratio differing from that in the bulk. The phase precipitating on the surface of unoriented parent grains may have preferential orientation owing to the orienting effect of single-crystal micrograins. Surface segregation markedly changes the composition of the solid solution toward disproportionation, leading to the formation of TiO₂ and PbZrO₃ instead of PbTi_0.6Zr_0.4O₃.     

Ultra-thin and isolated dots in polycrystalline lead zirconate titanate films

Size effects with critical thickness or minimum volume for ferroelectricity are of importance in the application of polycrystalline PZT thin films as future memory devices and as storage media. Isolated dots of perovskite phases in the matrix of pyrochlore were synthesized by isothermal annealing through transformation from amorphous to perovskite. Control of the transformation kinetics allows us to produce the isolated ferroelectric dots with a diameter of 50 nm. Domain structure of the isolated dots is also studied by piezoresponse force microscopy. As prepared, all isolated dots contain perpendicularly polarized monodomains. Domain structures and switching behaviors of the isolated dots are similar to those of the single crystalline PZT films. Polycrystalline PZT films with a thickness of 50 nm were also investigated. They show excellent piezoresponse properties and switching behaviors. Ultra-thin polycrystalline PZT films can play a major role in the application of future ferroelectric memories and field-effect transistors as well as for storage media using the local probe technique.     

Densification of sintered lead zirconate titanate by hot isostatic pressing

The effects of hot isostatic pressing (HIPing) on sintered lead zirconate titanate are presented. Densities up to 98% were obtained by HIPing for 1 h at 1300°C with argon gas pressures of either 20.7 or 138 MPa. The microstructural changes observed after HIPing, and the rapid initial kinetics for densification and pore shrinkage, indicate that prssure-enhanced grain rearrangement and solution-precipitation processes are primarily responsible for densification. The persistance of large voids after HIPing suggests that it may be impossible to completely eliminate gross processing-related defects in lead zirconate titanate by HIPing.