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.     

Particle Formation During Spray Pyrolysis of Lead Zirconate Titanate

A twin-fluid atomization spray pyrolysis technique has been used to produce lead zirconate titanate (PZT) powders from a sol–gel precursor solution. Samples were removed from ports sited along the reactor in order to examine particle development at progressive stages of pyrolysis. The total time in the reactor was 2.6 s. The size and shape of the particles showed no change between the first port (190°C) and the hottest part of the reactor (820°C), indicating that the physical structure of the particles was established during the initial drying stages. The powders were mainly composed of spherical particles, but irregular forms were also present, which were thought to result from the inward collapse of hollow gelatinous particles. Crystallization of PZT commenced at around 700°C, initially to a pyrochlore or fluorite intermediate phase, with the desired perovskite phase developing between 790°C and 815°C. However, a minor amount of the pyrochlore/fluorite phase persisted in the final powder. The final powders also contained basic lead carbonate, 2PbCO₃·Pb(OH)₂, which existed in the form of elongated crystallites on the surface of the PZT particles.     

Lead Zirconate Titanate Fiber/Polymer Composites Prepared by a Replication Process

The woven replication process was used to fabricate lead zirconate titanate (PZT)/polymer composites with 1–3, 2–3, and 3–3 connectivities by starting with novoloid-derived carbon fiber, woven fabric, and nonwoven felt templates, respectively. Activated carbon-fiber template material was impregnated with PZT by soaking it in a solution containing stoichiometric amounts of dissolved lead, zirconium, titanium, and niobium ions. Heat treatment burned out the carbon, leaving a PZT replica with the same form as the template material. Replicas were sintered in a controlled atmosphere and backfilled with an epoxy polymer to form final composites. This method, which is believed to be adaptable for mass production, is capable of producing composites with extremely fine microstructures. Woven composite samples have fiber tow diameters of 200 to 250 μm and spacings between tows of about 150 to 250 μm. Average d ₃₃= 90 pC/N, g ₃₃= 211 mV · m/N, and d_hg_h hydrophone figure of merit of 2100 × 10⁻¹⁵ m²/N values are reported for woven PZT/polymer composites.     

Ferroelastic Properties of Lead Zirconate Titanate Ceramics

To increase the reliability of multilayer actuators, calculation of the mechanical stress inside the device during operation is important. This paper shows that the small-signal value of the elastic constant s is not sufficient to describe the complicated behavior of lead zirconate titanate (PZT) ceramics. Therefore, compressive strain and depolarization have been measured as a function of large-signal stress applied parallel to the poling direction. The nonlinear dependence of the strain and depolarization can clearly be explained by domain processes. Soft and hard PZT ceramics have been investigated. In hard PZT, domain switching appears at higher stresses than in soft PZT. Moreover, in hard PZT, the domains partly switch back during unloading. The critical stress (coercive stress) necessary for a domain-switching process shows a dependence on the Zr:Ti ratio that is quite similar to the dependence of the electric coercive field. The influence of an electric field applied parallel to the poling direction and superimposed on the compression experiment also has been examined. The coercive stress depends linearly on the electric field. The linear coefficient of this relation is given by the ratio of depolarization to compressive strain caused by domain switching.     

Properties of Lead Zirconate Titanate Thin Films Prepared Using a Triol Sol–Gel Route

Microstructure and phase development during the thermal decomposition of sol–gel precursor coatings of PbZr_0.53Ti_0.47O₃ on platinized silicon substrates have been investigated for a triol sol–gel route. The single-layer, 0.4 μm PZT films were heated from below the substrate, over the temperature range 350–600°C, using a calibrated hot plate. The first crystalline phase to appear was a PbPt₃ intermetallic phase at the Pt/PZT interface. Although perovskite PZT formed at ca. 500°C, heating at higher temperatures, for example 550°C for 30 min, was required to develop ferroelectric hysteresis loops. However, the rather low value of remanent polarization, P _r= 11 μC·cm⁻², was consistent with incomplete crystallization at 550°C. The values of remanent polarization increased with increasing processing temperatures, reaching 21 μC·cm⁻² for samples heated at 600°C, with a corresponding E _c value of 57 kV·cm⁻¹. Distinctive spherical precipitates up to ca. 50 nm in size have been identified by TEM in the lower portions of otherwise amorphous coatings, after heating at around 350–400°C. Although their precise composition could not be identified, they were mostly Pb-rich, and it is speculated that they form due to reduction of some of the lead(II) acetate starting reagent, to atomic Pb during the early stages of thermal decomposition of the organic components of the gel; it is possible that subsequent reactions occur to form lead oxides or carbonates. High levels of porosity were present in many of the fully crystallized films. The possible reasons for this are discussed.     

Lead Zirconate Titanate Prepared from Different Zirconium and Titanium Precursors by Sol-Gel

Modified sol-gel processes have been developed for the preparation of lead zirconate titanate (PZT) (52/48) powders. These processes use different starting sources to introduce the titanium and zirconium components, namely tetraethyl orthotitanate, titanium isopropoxide, or titanium diisopropoxide bis(2,4-pentanedionate) for titanium and zirconium propoxide or zirconium acetylacetonate for zirconium. To achieve stable and homogeneous precursor systems, several solvents (acetic acid, 1,2-propanediol, propanol, and distilled water) and chemical modifying additives, such as acetylacetone and nitric acid, were also introduced for the preparation processes. The influence of the different precursors on the crystallization behavior of the sol-gel-derived powders was studied. Well-crystallized single-phase PZT powders were obtained after heat treatment at 600°C for 1 h. The powders obtained sintered well at 1000°C/2 h and a homogeneous microstructure with small grain sizes was obtained.     

锆钛酸铅纳米粉体的凝胶燃烧法制备及表征

以偏钛酸、双氧水、氨水、乙酸铅和硝酸锆为原料,乙二胺四乙酸(ethylene diamine tetraacetic acid,EDTA)为络合剂,柠檬酸为燃烧剂,采用凝胶燃烧法制备得到了锆钛酸铅(PbZr0.52Ti048O3,PZT)纳米粉体.首先,按相同摩尔比将偏钛酸溶于双氧水和氨水的混合溶液中,再加入适量的柠檬...     

Controlled Crystallization in Lead Zirconate Titanate Glass-Ceramics Prepared by the Sol-Gel Process

Lead titanate and lead zirconate titanate grains were grown in situ from lead-titanium-boron-silicon and lead-zirconium-titanium-boron-silicon gels prepared via the sol-gel method. The lead zirconate titanate grains were much smaller and more uniform than lead titanate grains grown from gels of similar composition. The crystallization mechanisms of the two systems were studied via scanning electron microscopy, X-ray diffractometry, Raman spectroscopy, and differential thermal analysis. Crystallization had a tendency to begin near the surface or at defects in the lead titanate system, whereas it was controlled by the original precipitated nuclei of tetragonal zirconia particles in the lead zirconate titanate system. Controlled bulk crystallization may explain the finer structure of the resultant lead zirconate titanate glass-ceramic.     

Electromechanical Properties of Lead Titanate Zirconate Ceramics with Lead Partially Replaced by Calcium or Strontium

By partially substituting Sr for Pb in ceramic lead titanate zirconate compositions near the morpho-tropic boundary, dielectric constants greater than 1300 can be obtained along with planar couplings of about 0.50. Calcium also raises the dielectric constant, but the planar coupling level is considerably lower than that obtained with Sr. Other effects noted with Sr are a lowering of the Curie temperature, a shift in the morphotropic boundary toward the rhombohedral side, and a decrease in the distortion from cubic symmetry. In addition, Sr was found to be effective as a fluxing agent.     

Fabrication and Electrical Properties of Lead Zirconate Titanate Thick Films

Thick films of lead zirconate titanate of the morphotropic phase boundary composition, Pb(Zr_0.52Ti_0.48)O₃, have been fabricated on platinum-buffered silicon using a modified sol–gel spin-coating technique. Crack-free films of 12-μm thickness can be uniformly deposited on 3-in.-diameter wafers with high yield and properties comparable to those of bulk ceramics. The thickness dependence of film structure and the dielectric, ferroelectric, and piezoelectric properties have been characterized over the thickness range of 1–12 μm. A strong (100) texture develops as film thickness increases above 5 μm; the films were marked by saturation values of longitudinal piezoelectric coefficient d ₃₃, 340 pC/N; remanent polarization, 27 μC/cm²; and dielectric permittivity, 1450. PZT films in this thickness range are extremely well-suited to application as electromechanical transduction media in silicon-based microelectromechanical systems (MEMS).     

Low-Temperature Preparation of Nanocrystalline Lead Zirconate Titanate and Lead Lanthanum Zirconate Titanate Powders Using Triethanolamine

Nanocrystalline lead zirconate titanate (PZT) powders, with a Zr:Ti ratio of 60:40, have been prepared from a solution of triethanolamine (TEA) and Ti⁴⁺, Zr⁴⁺, and Pb²⁺ ions. The metal ions were in solution through complex formation with TEA. The soluble metal-ion–TEA complex formed the precursor material when it was completely dehydrated. Heat treatment of the precursor at 450°C resulted in single-phase PZT powders. 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 and transmission electron microscopy studies, was ∼20 nm. PZT powders modified with 3 mol% of lanthanum (PLZT) also were prepared through this route and were investigated via XRD studies. The dielectric constants of the PZT and PLZT powders were 12475 and 11262, and their corresponding Curie temperatures were 362° and 315°C, respectively.     

Thermal Depoling Effects on Anisotropy of Lead Zirconate Titanate Materials

Changes in elastic anisotropy and fracture toughness anisotropy of a lead zirconate titanate (PZT) piezoelectric material as a function of depoling temperature were investigated using ultrasound and Vickers indentation. A gradual transition from anisotropic to isotropic properties occurs with increased depoling temperatures at and above the Curie temperature. Depoling is also evident through changes in domain character revealed by X-ray diffraction. The relationship between the mechanical properties and domain structure variation with respect to different depoling conditions is discussed.     

Synthesis of Lead Nickel Niobate–Lead Zirconate Titanate Solid Solutions by a B-site Precursor Method

A modified processing method for lead nickel niobate–lead zirconate titanate (Pb(Ni_1/3Nb_2/3)O₃–Pb(Zr,Ti)O₃, PNN–PZT) solid solutions is presented. This method is based on the high-temperature synthesis of a precursor that contains all the B-site cations (Ti, Zr, Ni, and Nb). This synthesis yields a diphasic mixture that contains a ZrTiO₄-like phase and a rutile-like phase. Both phases exhibit a cationic valence of 4; thus, it is concluded that the mixing of Ni and Nb cations is adequate for the preparation of PNN–PZT solid solutions. Indeed, a pure perovskite phase has been obtained after calcination with lead oxide for compositions that contain 40 and 50 mol% PNN. Moreover, their electromechanical properties have been shown to be superior to values reported for standard columbite routes. This conclusion has been interpreted in terms of enhanced chemical homogeneity.     

Preparation and Properties of Lead Zirconate Stannate Titanate Sintered by Spark Plasma Sintering

Lanthanum-doped lead zirconate stannate titanate ceramics were successfully compacted to full density by spark plasma sintering (SPS). SPS samples densified at 900° or 950°C exhibit nearly full density and fine grain size (about 300 nm). Compared with samples from conventional sintering (CS), SPS samples show larger permittivity accompanied by a deterioration in dielectric loss and special strain hysteresis loops similar to those of ferroelectric relaxors, with a diffuse AFE–FE phase transition and less field-induced longitudinal strain. The differences in the properties of SPS and CS materials are attributed to the variations of the resultant microstructures, especially the grain size, of the ceramics.     

Electric Fatigue in Ferroelectric Lead Zirconate Stannate Titanate Ceramics Prepared by Spark Plasma Sintering

Ferroelectric lead zirconate stannate titanate ceramics were prepared by spark plasma sintering (SPS). Compared with its counterpart densified by conventional sintering (CS), the SPS material shows a smaller remanent polarization and maximum strain as well as a higher coercive field. Electric fatigue in both materials was investigated. In contrast to CS samples, the SPS specimens show a lower resistance to bipolar electric cycling, characterized by a faster decrease in remanent polarization and maximum strain at cycle number below 10^6.5 and a subsequent slower reduction of the properties at high cycle numbers up to 10⁸.     

Electric Fatigue in Antiferroelectric Lead Zirconate Stannate Titanate Ceramics Prepared by Spark Plasma Sintering

The fatigue behavior of lead zirconate stannate titanate (PZST) ceramics prepared by spark plasma sintering (SPS) was investigated. Polarization and strain hysteresis loops were monitored. The material shows a high resistance to fatigue because of bipolar electric cycling. Both maximum strain and switchable polarization first show a fatigue stage 0 to 10⁵ cycles and then a fatigue-free period up to 10⁸ cycles. The maximum losses of maximum strain and switchable polarization are 18% and 10% of their initial values, respectively. The dominant fatigue mechanism is assigned to the pinning of domain walls by charged defects.     

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.     

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...     

Properties of Lead Zirconate Titanate Thick-Film Piezoelectric Actuators on Ceramic Substrates

Lead zirconate titanate (PZT) is a piezoelectric material that can sense or respond to mechanical deformations and can be used in ceramic electro-mechanical systems (C-MEMS). The microstructural, electrical, and piezoelectric characteristics of thick PZT films on low-temperature cofired ceramics (LTCC) and alumina substrates were studied. The PZT composition was prepared with low-melting-point additives in order to decrease the sintering temperature and to be compatible with thick-film technology. The integration of the PZT thick-film materials on ceramic substrates could lead to degradation of the PZT's characteristics due to the interactions between an active PZT layer and a substrate, particularly with glassy LTCC material. To minimize the interactions with LTCC substrates, an intermediate PZT barrier layer was integrated. The value of the piezoelectric coefficient d ₃₃ was found to be up to 120 pC/N on an alumina substrate and approximately 50 on an LTCC substrate. Based on these results, a cantilever-type actuator was designed and fabricated on alumina substrates. Under an applied voltage of 200 V, the maximum tip deflection was about 5 μm.     

Electromechanical Properties of Lead Titanate Zirconate Ceramics Modified with Certain Three-or Five-Valent Additions

When small amounts of lanthana, neodymia, niobia, or tantala are added to lead titanate zirconate compositions near the morphotropic (rhombohedral-tetragonal) phase boundary, the modified ceramics show piezoelectric planar coupling coefficients of about 0.50 and substantially increased dielectric constants of up to 1545. The mechanical Q factor is decreased to about 70, and there is a marked increase in volume resistivity at temperatures up to 500°C. Other effects noted are better shelf-aging characteristics, improved stability with respect to temperature dependence of resonant frequency, and a lowering of the Curie temperature. Except with neodymia, a definite refinement of the grain structure is also observed. By similar modification of Pb_0.95Sr_0.05(Zr._0.54 Ti_0.45)O₃ dielectric constants up to 1792 are obtained along with planar couplings of at least 0.49.