Size effect for lead zirconate titanate nano-particles with PZT (40/60) composition

This paper focuses on the size effect of lead zirconate titanate. Pb (Zr_0.4 Ti_0.6) O₃ (PZT40) nano-partilces with different sizes were prepared by the sol–gel method. The crystal size and structure were determined by X-ray diffraction. As a result the c/a ration (terragonality) was close to 1 with decreasing particle size. Raman spectra for PZT40 nano-particle of various sizes have been observed to exhibit a decrease in the soft mode at around 35 nm, suggesting the existence of a critical size of the PZT40 particle. The temperature dependence of Raman spectra clearly revealed that the Curie temerature for PZT40 nano-partilces shifted toward lower temperatures due to the size effect. The intrinsic dielectric onstants of PZT40 nano-particles calculated by the Laddne–Saches–Teller relation increased with decreasing particle size. These results show that Raman scattering is a powerful tool to investigate forrelectric materials.     

Millimetre-sized hollow spheres of lead zirconate titanate by a sol-gel method

Hollow spheres of lead zirconate titanate (PZT) [chemical formula Pb(Zr_0.52Ti_0.48)O₃)], with outer diameter of 1–2 mm and a wall thickness of about 100 m, were fabricated by gellation of a PZT sol inside solid polymer spheres and then burning the polymer out. Monomodally sized polyacrylamide spheres, with diameter 1.40–1.90 mm, were soaked in a PZT sol, prepared by dissolving Pb(NO₃)₂, zirconiumn-butoxide and titanium isopropoxide inN, N-dimethylformamide. The absorbed sol was then gelled beneath the surface of the polymer sphere by the action of NH₃. Upon calcination of the spheres at 850 °C for 4 h in air, hollow spheres of pure PZT perovskite phase (as identified by X-ray diffraction patterns) were obtained. The density of the hollow spheres was 1.13gcm^–3, while that of the wall of the spheres was 3.10g cm^–3. The scanning electron microscopic examination of the broken spheres showed that the inner surface of the spheres contained rib-like structures, which provided strength to the hollow spheres. The planar coupling factor,k _p, of six hollow spheres, placed at a close-packed arrangement in a plane, was 0.22, indicating the possibility of fabrication of low-density transducer arrays.     

Direct precipitation of lead zirconate titanate by the hydrothermal method

Direct precipitation of fine powders of lead zirconate titanate (PZT) in the complete range of solid solution, is investigated under hydrothermal conditions, starting from lead oxide and titania/zirconia mixed gels. The perovskite phase is formed in the temperature range of 165 – 340°C. Sequence of the hydrothermal reactions is studied by identifying the intermediate phases. The initial formation of PbO: TiO₂ solid solution is followed by the reaction of the same with the remaining mixed gels giving rise to X-ray amorphous PZT phase. Further, through crystallite growth, the X-ray crystalline PZT is formed. This method can be extended for the preparation of PLZT powder as well. The resulting powders are sinterable to high density ceramics.     

Theoretical and numerical predictions of the electromechanical behavior of spiral-shaped lead zirconate titanate (PZT) actuators

Presents a two-dimensional analytical model of a spiral-shaped PZT ceramic actuator. Developed using elasticity theory and a zero-stress assumption, the theoretical analysis has been formulated for a piecewise semicircular representation of the spiral-shaped actuator. Closed-form solutions of the tangential displacement of the equivalent spiral under applied electrical field in the poling direction have been obtained. To develop confidence in the theoretical model, results are compared with those obtained using finite element analysis (FEA). Results from both are then compared with previously reported experimental findings, and reasonable agreement is achieved     

Electrophoretic deposition of lead zirconate titanate (PZT) powder from ethanol suspension prepared with phosphate ester

The formation of thick PZT films via electrophoretic deposition (EPD) was studied. The colloidal suspension of a nano-sized PZT powder dispersed in ethanol was prepared using a phosphate ester (PE) as a dispersant. The amount of PE addition on the stability of the PZT suspension has been investigated by measuring the pH and conductivity of the suspension, deposition weight and the relative density of the PZT green compacts. The effect of the applied voltage on the relative green density was also determined as a function of the wt% PE. The composition and microstructure of the sintered PZT ceramics were characterized by XRD and SEM. The electrical properties of the PZT ceramics were also investigated.     

Hydrothermal synthesis of fibrous lead titanate powders

A fibrous lead titanate (PbTiO₃) powder with light-yellow colour has been prepared by hydrothermal synthesis. The influences of Pb/Ti ratio (0.3 to 1.0) in the mixture and reaction time on the formation of fibrous PbTiO₃ under hydrothermal conditions have been investigated. The preferable conditions for preparing fibrous perovskite-type PbTiO₃ from fibrous potassium titanate are that the Pb/Ti ratio is 1.0, reaction temperature 150 °C and time 72 h. The particles of fibrous powder of perovskite type are usually less than 2 m in diameter and more than 50 m in length. The fibrous morphology is essentially unchanged up to about 650 °C, but it disappeared after heating to 1000 °C.     

Low-temperature processing and characterization of single-phase PZT powders by sol-gel method

A new sol-gel system using acetoin was developed and employed for the fabrication of PZT powders and films with compositions near the morphotropic phase boundary Pb(Zr_0.52Ti_0.48)O₃. Acetoin was used as chelating agent to replace the highly toxic methoxyethanol used in previous formulations. This route simplified the chemical processing of PZT-based solutions. Powders were completely crystallized by about 450 °C and contained the ferroelectric perovskite single phase. The firing temperature and time were to be the most important variables. Metallic lead formed only when excess Pb was incorporated. The precursor and the heat-treated powders have been characterized by using thermal analysis and X-ray diffractometry (XRD) studies. The average particle size, as measured from X-ray line broadening, was ∼35 nm.     

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.     

A modified two-stage mixed oxide synthetic route to lead zirconate titanate powders

An approach to synthesis lead zirconate titanate [Pb(Zr_1−xTi_x)O₃; PZT] powders with a modified two-stage mixed oxide synthetic route has been developed. To ensure a single-phase perovskite formation, an intermediate phase of zirconium titanate (ZrTiO₄) was employed as starting precursor. The formation of perovskite phase in the calcined PZT powder has been investigated as a function of calcination temperature, soaking time and heating/cooling rates by differential thermal analysis (DTA) and X-ray diffraction (XRD) techniques. The morphology evolution was determined by scanning electron microscopy (SEM) technique. It has been found that the unreacted PbO and ZrTiO₄ phases tend to form together with PZT, with the latter appearing in both tetragonal and rhombohedral phases, depending on calcination conditions. It is seen that optimisation of calcination conditions can lead to a 100% yield of PZT in a tetragonal phase.     

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

A novel sol-hydrothermal route to prepare lead zirconate titanate (PZT) fine particles is presented, which combined the conventional sol–gel process and the hydrothermal method. The effects of experimental parameters including sol/(sol + water) ratio, reaction temperature and reaction time on the product powders were investigated. The prepared PZT powders were characterized by XRD, SEM/EDS, and Raman techniques. The results indicated that the optimal synthesis conditions were sol/(sol + water) = 20%, 200 °C, 8 h. The obtained powders with an average particle size of 700 nm, were phase pure perovskite PZT with cubic-shaped morphology, and the reaction temperature was as low as 150 °C, which was comparatively lower than that synthesized by the normal sol–gel route. It was supposed that the sol precursor and hydrothermal environment played important roles in the formation of the PZT fine powders at low temperature and low mineralizer concentration.     

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.     

Control of the particle size and morphology of hydrothermally synthesised lead zirconate titanate powders

The particle size and morphology of hydrothermally synthesised lead zirconate titanate (PZT) powders can be controlled by concentrations of the mineraliser such as potassium hydroxide (KOH), and the hydrothermal synthesis temperature and time, which all influence the particle nucleation and growth mechanisms. The mineraliser is crucial in facilitating both the in-situ transformation process during the nucleation stage and the nuclei-coagulation process during the subsequent growth stage. Its concentration must be high enough to ensure the formation of only pure perovskite PZT particles but low enough to prevent excessive PZT particle growth. The minimum necessary mineraliser concentration has, however, strong dependence on both the hydrothermal synthesis temperature and chemical environment in hydrothermal solution. Thus, perovskite PZT powders with ca. 200 nm particle size and narrow particle size distribution can be synthesised hydrothermally at 300°C using KOH as a mineraliser with a minimum concentration of 0.4 M.     

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.     

Low-temperature crystallization of sol-gel-derived lead zirconate titanate thin films using 2.45 GHz microwaves

Lead zirconate titanate (PZT) thin films of thickness 420 nm were deposited on Pt/Ti/SiO₂/Si substrate using a spin coating sol-gel precursor solution, and then annealed using 2.45 GHz microwaves at a temperature of 450 °C for 30 min. The film has a high perovskite content and high crystallinity with a full width at half maximum of 0.35°. The surface roughness of the PZT thin film was 1.63 nm. Well-saturated ferroelectric properties were obtained with a remanent polarization of 46.86 μC/cm² and coercive field of 86.25 kV/cm. The film also exhibited excellent dielectric properties with a dielectric constant of 1140 and a dissipation factor of 0.03. These properties are superior to those obtained by conventional annealing at a temperature of 700 °C for 30 min.     

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.     

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.     

Structural and ferroelectric properties of europium doped lead zirconate titanate thin films by a sol-gel method

Using a sol-gel method, rare earth element europium doped lead zirconate titanate thin films with a pure perovskite structure were obtained. The effects of excess lead and pyrolyzing temperature on the crystalline structure of the thin films were investigated using X-ray diffraction. Their ferroelectric and dielectric properties were determined by P-E loop and impedance measurements. The remnant polarization is 23.5 μC/cm² and the coercive electric field strength is 5.5 kV/mm. The dielectric constant and the dissipation factor is approximately 950 and 0.07, respectively.     

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.     

Wafer scale lead zirconate titanate film preparation by sol-gel method using stress balance layer

In this paper, platinum/titanium (Pt/Ti) film was introduced as a residual stress balance layer into wafer scale thick lead zirconate titanate (PZT) film fabrication by sol-gel method. The stress developing in PZT film's bottom electrode as well as in PZT film itself during deposition were analyzed; the wafer curvatures, PZT crystallizations and PZT electric properties before and after using Pt/Ti stress balance layer were studied and compared. It was found that this layer is effective to balance the residual stress in PZT film's bottom electrode induced by thermal expansion coefficient mismatch and Ti diffusion, thus can notably reduce the curvature of 4-in. wafer from − 40.5 μm to − 12.9 μm after PZT film deposition. This stress balance layer was also found effective to avoid the PZT film cracking even when annealed by rapid thermal annealing with heating-rate up to 10.5 °C/s. According to X-ray diffraction analysis and electric properties characterization, crack-free uniform 1-μm-thick PZT film with preferred pervoskite (001) orientation, excellent dielectric constant, as high as 1310, and excellent remanent polarization, as high as 39.8 μC/cm², can be obtained on 4-in. wafer.