Crack-Growth-Velocity-Dependent R-Curve Behavior in Lead Zirconate Titanate

Crack-velocity ( v – K ) curves and crack-resistance ( R ) curves for unpoled ferroelectric and ferroelastic lead zirconate titanate (PZT) were determined for long cracks in compact-tension (CT) geometry using an in situ fracture device on the stage of an optical microscope. The steady-state crack length and the plateau value of R -curves measured at controlled constant velocities increased with increased velocity. The plateau value for 10⁻⁶ m/s was 1.2 MPa·m^1/2 after 1.3 mm of crack extension and for 10⁻⁴ m/s was 1.4 MPa·m^1/2 after 2.2 mm.     

R-Curve for a Lead Zirconate Titanate Ceramic Obtained from Tensile Strength Tests with Knoop-Damaged Specimens

A procedure was used that made it possible to determine the R -curve for piezoelectric ceramics from tensile strength tests conducted with Knoop-damaged specimens. The resulting crack-tip toughness K _I0 was 0.6 MPa·m^1/2, and the R -curve starting from this value increased to 1.4 MPa·m^1/2 within a 0.7 mm crack extension.     

Electrophoretic Deposition of Lead Zirconate Titanate Ceramics

Electrophoretic deposition (EPD) of submicrometer lead zirconate titanate (PZT) powders in ethanol was conducted to form thick green PZT films up to 160 μm thick. The PZT colloid stability, as a function of pH, was studied by zeta-potential measurement. The electrical condition of the suspension was quantified by conductivity measurement at various pH values. The effect of different applied current densities on the deposition mass was investigated. A kinetic model for the constant-current-density EPD process, taking into account the particle concentration variation, was also examined, based on the experimental results obtained in the present work. An empirical relationship between the kinetic constant and the applied current density has been proposed.     

Formation of Lead Zirconate Titanate Powders by Spray Pyrolysis

Twin-fluid atomization spray pyrolysis (SP) has been investigated for the production of lead zirconate titanate (PZT) powders, using aqueous solutions of lead acetate and zirconium and titanium alkoxide precursor reagents. The particle size distribution of the PZT powder showed a d ₅₀ value of 0.3 μm, but with a small fraction of relatively large particles, several micrometers in size. Most particles were spherical but many of the largest particles, in the size range ca. 1–5 μm, were irregular. It was demonstrated that the morphology of the final PZT powder was controlled by decomposition processes occurring during the initial drying stages, at ≤200°C. A pyrochlore or fluorite-type intermediate crystalline phase was present in the final powders, but when the maximum reactor temperature was raised, and/or when the levels of excess lead in the starting solutions were increased, the proportion of the desired perovskite phase increased. However, at the highest process temperatures studied, ∼900°C, small crystallites of another phase formed on the surface of the PZT particles; these were probably lead oxide carbonate particles. Overall, a starting solution composition containing around 5 mol% excess Pb, and a maximum reactor temperature of 800°C, were selected as offering the most suitable conditions for producing PZT (52/48) powder, with minimal secondary phases(s). Preliminary densification studies showed that the powders could be sintered at 1150°–1200°C to give pellets of 95%–96% theoretical density.     

Effect of Lead Zirconate Titanate Seeds on PtxPb Formation during the Pyrolysis of Lead Zirconate Titanate Thin Films

Lead zirconate titanate (PZT) thin films were prepared on platinized silicon substrates by dip-coating using a modified diol-based sol–gel route without and with up to 5 mol% PZT nanometric seeds dispersed in the precursor sol. A metastable intermetallic Pt _x Pb phase formed at the early stages of heat treatment. XRD, TEM, and RBS revealed that the thickness and stoichiometry of the Pt _x Pb layer varied with the concentration of seeds and heat treatment of the films. The relation of the Pt _x Pb layer to the final crystalline texture of the PZT thin films is reported and discussed.     

Lead Zirconate Titanate Particle Dispersion in Thick-Film Ink Formulations

Diverse device applications for lead zirconate titanate (PZT) ceramics in thick-film form are currently in active development. In the present study, the particle dispersion properties of thick-film ink formulations containing PZT powder have been determined using rheological measurements. Although all of the eight commercially available dispersants tested are more effective than the terpineol solvent alone in decreasing attractive interparticle forces in suspensions, the best dispersant identified for hard and soft PZT powders is a phosphate ester oligomer. This dispersant is extremely efficient, and its use in thick-film ink formulations results in viscosity decreases of 50% at low shear rates (10 s⁻¹) and 30% at high shear rates (100 s⁻¹) compared with current ink formulations containing no dispersant. The effects upon rheology of the order of addition of components in the processing of inks have been studied, with the most effective processing route using a fugitive solvent that probably facilitates uniform coverage of the particle surfaces by the dispersant molecules. Modeling of the rheological profiles of inks indicates that the use of a dispersant decreases the depth of the primary minimum in the interparticle potential by a factor of 3. Demonstrated advantages of the use of a dispersant in PZT thick-film inks include improved microstructural homogeneity in the green body and the ability to formulate printable inks with higher solids loadings. No adverse effects of the dispersant upon the dielectric and piezoelectric properties of bulk PZT samples are found following burnout and sintering.     

Crack–Tip Toughness of a Soft Lead Zirconate Titanate

Crack–opening displacement (COD) measurements were performed on a commercial lead zirconate titanate (PZT). The intrinsic fracture toughness (or crack–tip toughness) of this material was determined using a new evaluation procedure, which takes into account the near–tip CODs and complete crack profile CODs. The crack–tip toughness K _I0 was determined from an extrapolation of COD data obtained at various loading stages, thus avoiding the complications caused by subcritical crack growth in PZT. Results for plane strain and plane stress condition are presented.     

Structural and Property Evolution of Aqueous-Based Lead Zirconate Titanate Tape-Cast Layers

We have developed aqueous suspensions of lead zirconate titanate (PZT) and an acrylic latex emulsion binder for tape casting. Rheological measurements were conducted to optimize their flow behavior at high solids volume fraction (φ_solids). Concentrated suspensions (φ_solids > 0.45) were tape cast onto a silicone-coated mylar carrier film, and the effect of cellulose (a viscosifier) and surfactant additions on wetting behavior was studied. Drying stress measurements were performed on tape-cast layers using a substrate deflection technique. The initial period of stress rise was analogous to that observed for binder-free ceramic films, whereas the stress decay was influenced by latex coalescence. Tape-cast layers exhibited a constant PZT volume fraction of 0.49 and uniform binder distribution independent of the PZT/latex volume ratio. The dielectric and piezoelectric properties of sintered multilayer samples were comparable to those obtained for bulk, isopressed samples. Our work provides guidelines for developing aqueous formulations for tape casting complex electroceramic oxide layers.     

Strong Electromechanical Response in Lead Zirconate Titanate Metamaterials

As a class of technically important functional materials, Pb(Zr,Ti)O₃ (PZT)‐based materials have been widely used in different types of piezoelectric devices. These materials are also ferroelectrics, and the materials lose their piezoelectric properties above the Curie temperature, a drawback limiting applications of the materials at high temperatures. Designing piezoelectric metamaterials by exploiting the flexoelectricity of the PZT‐based materials is a possible solution to this issue. In this work, PZT‐based piezoelectric metamaterials can be designed by applying an asymmetric chemical reduction to PZT ceramics to produce a curvature. The reduced PZT ceramic wafers exhibit a high apparent piezoelectric response (>2900 pC/N), which can be sustained after a heat treatment at 550°C for 5 h, which is more than 250°C above their Curie temperature. A substantial piezoelectric response can also be directly measured well above the Curie temperature. The mechanism underlying this very high apparent piezoelectric response with high‐temperature stability is investigated. The experimental results suggest that the electromechanical response mainly originates from the flexoelectric effect when the reduction‐induced curvature is bent under stress. The formation of the curvature also causes strain gradient‐induced poling of the reduced materials, resulting in a weak piezoelectric response from partly oriented polarization, which partly contributes to the observed response.     

Directed Colloidal Assembly of Linear and Annular Lead Zirconate Titanate Arrays

Lead zirconate titanate (PZT) arrays for ultrasonic sensing applications in the 2–30-MHz frequency range were fabricated by robocasting, a directed colloidal assembly technique. Both linear and annular arrays were produced by robotically depositing a concentrated PZT gel-based ink to create high-aspect-ratio PZT elements (thickness ∼ 130 μm and height ∼1–2 mm) of varying pitch (∼250–410 μm). The arrays were densified and infiltrated with an epoxy resin to fabricate PZT–polymer composites with 2–2 connectivity. Their dielectric and piezoelectric constants were measured and compared with values obtained for bulk PZT and those predicted theoretically.     

Lead Zirconate Titanate Thin Films by Aerosol Plasma Deposition: Microstructure Analysis

Lead zirconate titanate (Pb(Zr,Ti)O₃, PZT) thin films were grown on silicon 〈100〉 substrate by aerosol plasma deposition (APD) using solid-state-reacted powder containing donor oxide Nb₂O₅ when keeping the substrate at room temperature and 200°C. Crystalline phases of the deposited films have been analyzed via X-ray diffractometry (XRD), and microstructure via scanning and transmission electron microscopy (SEM and TEM). Cross-sectional TEM revealed that the microstructure comprised several layers including the deposited PZT film and the platinum-electrode-and-titanium-buffered layers on SiO₂–Si substrate. The Pt-electrode layer contained (111)_Pt twinned columnar grains with a slight misorientation and forming low-angle grain boundaries among them. The PZT layer contained randomly oriented grains embedded in an amorphous matrix. Some of the PZT grains, oriented with the zone axis Z = [[Twomacr]11]_PZT parallel to Z = [111]_Pt, were grown epitaxially on the Pt layer by sharing the (111)_PZT plane with the (111)_Pt twinned columnar Pt crystals. However, the existence of such an orientation relationship was confined to several nanosize grains at and near the PZT-Pt interface, and no gross film texture has been developed. An amorphous grain boundary phase, generated by pressure-induced amorphisation (PIA) in the solid state, was identified by high-resolution imaging. Its presence is taken to account for the densification of the PZT thin films via a sintering mechanism involving an amorphous phase on deposition at 25° and 200°C.     

二乙醇胺辅助溶胶-凝胶法低温合成锆钛酸铅纳米粉体

以醋酸铅[Pb（CH3COO）2^-33H20]、硝酸锆[Zr（N03）4^-5H2O]和钛酸四丁酯[Ti（C4H90）4]为原料,以二乙醇胺（diethanolamine,DEA）为聚合剂．用溶胶-凝胶法制备了锆钛酸铅（PbZrxTil-x03,PZT）纳米陶瓷粉体。研究了DEA对溶胶-凝胶法合成PZT陶瓷粉体的影响...     

Factors Determining Grain Orientation in Bismuth Sodium Potassium Titanate–Lead Zirconate Titanate Solid Solutions Made by the Reactive Templated Grain Growth Method

Grain-oriented Bi_0.5(Na_0.85K_0.15)_0.5TiO₃-Pb(Zr_{1− x} Ti _x )O₃ (BNKT-PZT) ceramics were prepared via the reactive templated grain growth method, using platelike Bi₄Ti₃O₁₂ particles. Factors that determine the degree of orientation were examined. Prereacted PZT gave a larger degree of orientation than PZT raw materials (PbO, ZrO₂, and TiO₂) in the 75BNKT-25PZT ( x = 0.5) system. Increases in the titanium concentration in the PZT of the 75BNKT-25PZT system and in the BNKT concentration in the y BNKT-(100 − y )PZT ( x = 0.5) system increased the degree of orientation. The direction of material transport between BNKT and PZT was important to obtain ceramics with a large degree of orientation.     

Differences in Tensile and Bending Strength for Knoop-Cracked Lead Zirconate Titanate Specimens

The strength of piezoelectric ceramics differs greatly in tension and bending tests. This effect, which is known to occur for specimens with a natural flaw population, also occurs in tests that involve Knoop-cracked specimens. In such samples, the linear-elastically computed bending strength is ∼35% higher than the tensile strength. Computation of the actual stress distribution in the bending bars has shown that these differences are predominantly caused by the nonlinearity and nonsymmetry of the deformation behavior.     

Effects of Solvent Mixtures on Dispersion of Lanthanum-Modified Lead Zirconate Titanate Tape Casting Slurries

The effects of xylenes/ethanol solvent mixtures on lanthanum-modified lead zirconate titanate (PLZT) nonaqueous suspensions were investigated by measuring sediment height, viscosity, and adsorption of dispersant. Well-dispersed colloidal suspensions were obtained in xylene-rich solvents with a minimum amount of menhaden fish oil as a dispersant. It was also shown that adsorption of dispersant on particle surfaces strongly depends on selection of solvent(s). The ratio of solvent mixture affects PLZT solids content of unfired tapes, in which using insufficient as well as excess dispersant could decrease the packing density of particles. Solubility of other organic additives, such as binder, was also considered when selecting a xylene/ethanol ratio.     

Fabrication of NiO Nanoparticle-Coated Lead Zirconate Titanate Powders by the Heterogeneous Precipitation Method

NiO nanoparticle-coated lead zirconate titanate (PZT) powders are successfully fabricated by the heterogeneous precipitation method using PZT, Ni(NO₃)₂·6H₂O, and NH₄HCO₃ as the starting materials. The amorphous NiCO₃·2Ni(OH)₂·2H₂O are uniformly coated on the surface of PZT particles. XRD analysis and the selected-area diffraction (SAD) pattern indicate that the amorphous coating layer is crystallized to NiO after being calcined at 400°C for 2 h. TEM images show that the NiO particles of ∼8 nm are spherical and weakly agglomerated. The thickness of the nanocrystalline NiO coating layer on the surface of PZT particle is ∼30 nm.     

Novel Synthesis Route to Make Nanocrystalline Lead Zirconate Titanate Powder

The present research describes synthesis of perovskite lead zirconate titanate (PZT) nanocrystalline mesoporous powders from the aqueous solutions of Pb²⁺, Zr⁴⁺, and Ti⁴⁺ metal ions using sucrose as a template material. Sucrose retains the metal ions in solution through complex formation. Dehydration and thermal decomposition of the metal ion–sucrose mass produces a large amount of gas, which helps to create porosity and high surface area in the final products. The particle size of the synthesized powder is between 50 and 60 nm, with a average specific surface area between 20 and 25 m²/g. The surface area increases as the amount of sucrose increases. Nanocrystalline PZT powder with high surface area can be useful for low-temperature sintering.     

Phase Stability and Ferroelectric Properties of Lead Strontium Zirconate Titanate Ceramics

The effect of compositional modifications on the field-induced phase-transition behavior and dielectric properties of strontium-doped lead zirconate titanate (PZT) ceramics was studied. PZT compositions with different strontium and titanium contents, within the general formula Pb_{1– x} Sr _x (Zr_{1– y} Ti _y )O₃ and located in the tetragonal antiferroelectric (AFE) and rhombohedral ferroelectric (FE) phase fields were prepared by tape casting and sintering. X-ray diffraction and polarization measurements were used to locate compositions suitable for investigation of the field-induced AFE–FE phase transition. The results indicated that a higher Sr²⁺ content decreased the polarization and hysteresis and increased the switching field; a lower Ti⁴⁺ content decreased the polarization and increased the switching field and hysteresis. A high room-temperature dielectric constant was obtained for compositions near the phase boundary. These results suggest that a combination of both A -site and B -site modifications can be used to tailor ferroelectric properties, such as the switching field and hysteresis, of these strontium-doped PZTs displaying a field-induced AFE–FE phase transition.     

Piezoelectric Lead Zirconate Titanate Ceramic Fiber/Polymer Composites

Piezoelectric lead zirconate titanate (PZT) ceramic fiber/polymer composites were fabricated by a novel technique referred to as "relic" processing. Basically, this involved impregnating a woven carbon-fiber template material with PZT precursor by soaking the template in a PZT stock solution. Careful heat treatment pyrolized the carbon, resulting in a PZT ceramic relic that retained the fibrous template form. After sintering, the densified relic was backfilled with polymer to form a composite. Optimized relic processing consisted of soaking activated carbon-fiber fabric twice in an intermediate concentration (405-mg PZT/(1-g solution)) alkoxide PZT solution and sintering at 1285°C for 2 h. A series of piezoelectric composites encompassing a wide range of dielectric and piezoelectric properties was prepared by varying the PZT-fiber orientation and polymer-matrix material. In PZT/Eccogel polymer composites with PZT fibers orientated parallel to the electrodes, K = 75, d ₃₃= 145 pC/N, d _h= 45 ± 5 pC/N, and d _hg_h= 3150 × 10⁻¹⁵ m²/N were measured. Furthermore, in composites with a number of PZT fibers arranged perpendicular to the electroded surfaces, K = 190, d ₃₃= 250 pC/N, d _h= 65 ± 2 pC/N, and d _h g_h= 2600 × 10⁻¹⁵ m²/N.     

Polymorphic Phase Transformation of Lead Monoxide and Its Influence on Lead Zirconate Titanate Formation

The polymorphic phase transformation of PbO from massicot to litharge phase is easily produced by mechanical force. The transformation is relatively quick by wet ball-milling. The additions of TiO₂ and ZrO₂ tend to retard it. A second-order exponential relation is observed between the fractional conversion and the milling time for pure PbO, PbO-TiO₂, and PbO-ZrO₂-TiO₂ systems with a rutile constituent. This exponential relation is changed into a first-order logarithmic relation when anatase instead of rutile is used. Although the PbO _ss phase is observed irrespective of the phase of the PbO in the raw materials, this PbO _ss peak is more obvious when massicot PbO or anatase TiO₂ is used. The formation of PbO _ss phase is also dependent on the reactivity of the ZrO₂, and its presence can affect the formation and piezoelectric properties of PZT ceramics.