Pb(Zr0.5, Ti0.5)O3 nanofibres by electrospinning

Lead zirconate titanate Pb(Zr_0.5, Ti_0.5)O₃ nanofibres with diameters ranging from 200–300 nm have been synthesized by calcination of the electrospun lead zirconate titanate/polyvinyl acetate composite fibres. The morphology and crystalline phase features of these lead zirconate titanate (PZT) nanofibres have been studied by various physico-chemical methods such as SEM, AFM, XRD and FT–IR. The formation of perovskite PZT phase was observed at temperatures as low as 550 °C.     

Effects of milling time and calcination condition on phase formation and particle size of lead titanate nanopowders prepared by vibro-milling

Effect of calcination conditions on phase formation and particle size of lead titanate (PbTiO₃) powders synthesized by a solid-state reaction with different vibro-milling times was investigated. Powder samples were characterized using XRD, SEM, TEM and EDX techniques. A combination of the milling time and calcination conditions was found to have a pronounced effect on the phase formation and particle size of the calcined PbTiO₃ powders. The calcination temperature for the formation of single-phase perovskite lead titanate was lower when longer milling times were applied. More importantly, by employing an appropriate choice of the milling time and calcination conditions, perovskite lead titanate (PbTiO₃) nanopowders have been successfully prepared with a simple solid-state reaction method.     

Phase evolution of electron-beam evaporated Pb(Zr,Ti)O3 thin films

Solid phase reactions among electron-beam deposited PbO, ZrO₂ and TiO₂ in the thin film state as distinct from those occurring in the bulk state are described under varied annealing conditions leading to growth of perovskite PZT phase. Loss of PbO by direct high temperature (700 °C) anneal led to the growth of cubic A₂B₂O_7−x pyrochlore as well as an AB₃O₇ phase of monoclinic structure. A lower temperature initial anneal at 600 °C in O₂ ambient minimises PbO loss through phase transformation to tetragonal Pb₃O₄ and better crystallised oxide phases partially react to form pyrochlore as well as perovskite PZT. This partial reaction is kinetically driven as it goes to completion in ∼4 h resulting in transformation of pyrochlore to perovskite phase. At high temperature (800 °C) A₂B₂O_7−x phase converts to PZT perovskite and the AB₃O₇ dissociate to yield TiO₂ secondary phase inclusion in the PZT film.     

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.     

PZT thin film preparation by pulsed DC magnetron sputtering

Pulsed DC magnetron sputtering was used in this study to prepare lead zirconate titanate (Pb(Zr_xTi_1−x)O₃, PZT) thin films. A single metallic target was used for the deposition onto a Pt/Ti/SiO₂/Si substrate and parameters such as: pulse frequency, duty cycle, O₂/Ar flow ratio controlled so as to analyze the effect of the parameters on thin film deposition rate, crystalline structure and morphology. After the deposition, the thin film was annealed in a rapid thermal annealing (RTA) furnace. The experimental results showed that, when the pulse frequency was in the range of 10 kHz-100 kHz, along with the lowering of frequency and the oxygen argon flow rate ratio, the deposition rate gradually increased and the formation of PZT thin film perovskite phase was enhanced; however, if the oxygen argon flow rate ratio was too high, it caused the PZT thin film to generate a pyrochlore phase. However, when the duty cycle was in the range of 95%-75%, the highest deposition rate and better perovskite phase could be obtained in the range of 75%-80%.     

Hydrothermal synthesis of lead doped barium titanate

Lead doped barium titanate was synthesized hydrothermally at 363 K for 140 h. A molar formula of Ba_(1–x)Pb _x TiO₃ was used, where x ranged between 0.025 and 0.75. The crystal structure, phase purity, and particle morphology was investigated by x-ray diffraction, Raman spectroscopy and electron microscopy. Under the synthesis conditions used, lead (Pb²⁺) was shown to incorporate into the perovskite structure when the dopant was kept below 20%. Above 20% Pb, other phases appeared and at 75% Pb no reaction to the perovskite structure took place. Unexpectedly, barium titanate containing from 2.5% Pb to 10% Pb appeared to be of orthorhombic symmetry. This was concluded by total pattern fitting of x-ray diffraction profiles and from splitting of the 222 reflection. The factors controlling the tendency for these materials to adopt orthorhombic symmetry as opposed to the more commonly observed tetragonal or cubic symmetries are briefly discussed.     

Electrorheological properties of novel piezoelectric lead zirconate titanate Pb(Zr0.5,Ti0.5)O3-acrylic rubber composites

Perovskite lead zirconate titanate, comprised of PbTi_1 ? xO₃ and PbZr_xO₃, was synthesized at a temperature below the Curie temperature, T_C. The tetragonal form obtained is a noncentrosymmetric structure capable of spontaneous polarization. FTIR spectra and XRD patterns confirm the successful synthesis of the lead zirconate titanate (PZT). PZT particles were mixed with an arcrylic rubber solution and cast as a thin sheet. SEM micrographs indicate that PZT particles are moderately dispersed in the acrylic rubber (AR71) matrix. Without electric field, the particles merely act as a reinforcing filler which can absorb and store additional stress. Under electric field, particle-induced dipole moments are generated, leading to interparticle interactions, and a substantial increase in the storage modulus. At a lead zirconate titanate volume fraction of 0.038600, the storage modulus response attains its maximum value with the corresponding storage modulus sensitivity value of 0.58 as the electric field strength is varied from 0 to 2 kV/mm.     

Structural and electrical studies of CeO2 modified lead zirconate titanate ceramics

The present study is an investigation of the structural and electrical properties of solid solution processed lead zirconate titanate (PZT) ceramics modified by CeO₂. The PZT composition studied is Pb(Zr_0.535Ti_0.465)O₃ modified with 0.0–0.2 mol % CeO₂. Studies of the loss of lead oxide during sintering have been performed. The lead loss increases with increasing Ce in the sample up to 0.1 mol % Ce and becomes nearly constant on further addition of Ce. The lattice parameters and cell volume of the tetragonal phase of PZT also increase with addition of Ce up to 0.1 mol % Ce. The lead loss and X-ray data indicate that Ce is being reduced to Ce³⁺ and is going onto the A-site of the PZT perovskite system. The study concludes that controlled modification of the MPB composition of PZT using 0.1 mol % CeO₂ results in substantial enhancement of piezoelectric strain coefficients, dielectric constant and electromechanical coupling coefficients.     

Powders of Pb(ZrxTi1−x)O3 by sol-gel coating of PbO

Powders of lead zirconate titanate (PZT) are prepared by coating a PbO powder with very fine particles containing titanium and zirconium derived from an alkoxide sol. The size of the particles in the coating increases from 10 nm to 100 nm with the increase in the pH during preparation from 3 to 10.5. The powders calcine at low temperature ( 600 °C) to single-phase PZT without the formation of any intermediate phase. The tetragonal and rhombohedral phases are found to coexist betweenx = 0.535 and 0.545. Careful calcination of the powders is needed to ensure removal of residual organics; otherwise the residual carbon reduces PbO to metallic lead leading to high currents during poling. Loss of lead on sintering is significantly lower (1.4 wt%) as compared to samples from conventional powders (6.4 wt%). Successful poling of the sintered samples is achieved when the powders are prepared without using sol stabilizers and are calcined without pelletizing. Washing of the powders is not helpful, perhaps because it leads to change in stoichiometry due to loss of material. A dielectric constant of 950 andd ₃₃ > 190 pCN^–1 are easily achieved.     

Effect of pH on the Crystallization of Homogeneously Precipitated Nanosized PZT Powder

Nanosized lead zirconate titanate (PZT) powder with Zr:Ti ratio in the morphotropic phase boundary region was synthesized by homogeneous precipitation of metal ions. The powder precipitated at 90°C and at pH 6.7 resulted single-phase perovskite lead zirconate titanate powder when calcined at 550°C and above for 4 hours in air. The solution pH and the precipitation temperature strongly affect the composition of the calcined powder. The results obtained by structural characterization of homogeneously precipitated powder were compared with that obtained from the conventional precipitation method using ammonia in terms of crystallization, homogeneity, and microstructure. The homogeneously precipitated powder showed smaller particle size, minimum agglomeration and uniform shape on calcination and annealing. Powdered samples that precipitated by homogeneous precipitation crystallized directly to perovskite PZT, without any intermediate pyrochlore phase formation. In contrast, the NH₃ precipitated powder converted to perovskite PZT via metastable pyrochlore and it showed phase segregation upon annealing at higher temperatures. The reaction kinetics has been studied by X-ray diffraction, differential thermal analysis, and differential scanning calorimetry.     

Size effect studies on nanocrystalline Pb(Zr0.53Ti0.47)O3 synthesized by mechanical activation route

The nanocrystalline lead zirconate titanate (PZT) with the composition Pb(Zr_0.53Ti_0.47)O₃ has been synthesized by mechanical activation, without calcination at intermediate temperature. The PZT powder that has been mechanically activated for 10, 20 and 30 h shows crystallite size of 15, 12 and 8 nm, respectively. Size effect on PZT formation, tetragonality factor and dielectric constant has been investigated in detail. TEM and AFM studies have been carried out to confirm the formation of nanocrystalline PZT. The temperature dependence of dielectric constant at different frequencies was also measured, to study the size effects in PZT ferroelectrics. The nanocrystalline PZT obtained by this route has high dielectric constant at Curie temperature in comparison to that prepared conventionally.     

Pb(Zr0.95Ti0.05)O3 powders prepared by aqueous Pechini method using one-step pyrolysis process: characterization and porous ceramics

Zr-riched lead zirconate titanate, Pb(Zr_0.95Ti_0.05)O₃ (PZT 95/5) powders were prepared using lead acetate, zirconium oxynitrate, and titanium sulfate by aqueous Pechini method. The chelation behaviors of metallic ions and citric acid were investigated and the development of the phase formation of perovskite structure was detected. PZT 95/5 powders were obtained directly from the as-synthesized gels by one-step pyrolysis process at 450 °C for 10 h. Perovskite phase was formed at about 450 °C and no distinct intermediates were obtained. There were some carbonates as impurities but they did not affect the formation of the complete perovskite phase of PZT 95/5 ceramics after sintering at 1,100–1,150 °C for 2 h. The decomposition of few organic residues among the one-step pyrolyzed powders could form uniform porous structure and the formation mechanism of porous ceramics was also presented.     

Effect of lead oxide on the dielectric characteristics of heterogeneous Pb(Zr, Ti)O3 + PbO films obtained by a two-stage method

We have studied changes in the dielectric properties of thin lead zirconate titanate Pb(Zr,Ti)O₃ (PZT) films, obtained using a two-stage ex-situ technology, as dependent on the microstructure of a perovskite phase and the content of microinclusions of excess lead oxide. The presence of these microinclusions leads to either anomalously low or high values of dielectric permittivity and anomalous pyroelectric response.     

Large electrocaloric effect of highly (100)-oriented 0.68PbMg1/3Nb2/3O3-0.32PbTiO3 thin films with a Pb(Zr0.3Ti0.7)O3/PbOx buffer layer

0.68PbMg_1/3Nb_2/3O₃-0.32PbTiO₃ (PMN-PT) thin films with a lead zirconate titanate Pb(Zr_0.3Ti_0.7)O₃ (PZT)/PbO_x buffer layer were deposited on Pt/TiO₂/SiO₂/Si substrates by radio frequency magnetron sputtering technique, and pure perovskite crystalline phase with highly (100)-preferred orientation was formed in the ferroelectric films. We found that the highly (100)-oriented thin films possess not only excellent dielectric and ferroelectric properties but also a large electrocaloric effect (13.4 K at 15 V, i.e., 0.89 K/V) which is attributed to the large electric field-induced polarization and entropy change during the ferroelectric-paraelectric phase transition. The experimental results indicate that the use of PZT/PbO_x buffer layer can induce the crystal orientation and phase purity of the PMN-PT thin films, and consequently enhance their electrical properties.     

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     

Microstructural characterization of donor-doped lead zirconate titanate films prepared by sol–gel processing

Lanthanum and niobium-doped lead zirconate titanate, Pb(Zr,Ti)O₃, (PZT) thin films were prepared on Pt/Ti/SiO₂/Si substrates by sol–gel processing. Films have a Zr/Ti ratio of 52:48 and tetragonal perovskite phase structure. The influence of donor dopants on the morphology, texture and defects of PZT films was studied using X-ray diffraction, X-ray photoelectron spectroscopy, atomic force microscopy, scanning electron microscopy, breakdown field strength and fatigue. Donor doping of PZT films results in increased breakdown field strength and improved fatigue properties. These originate from (i) the reduction of texture in the [111] and increase in the texture in [100]; (ii) lower porosity, smaller grain size and smoother surfaces; (iii) granular grain structure; and (iv) reduction in the oxygen vacancy concentration in the films.     

Structural studies of BiFeO3 modified BMZ-PT ceramics

Bismuth perovskites have been attracting attention as a family of piezoelectric ceramics in place of the widely used Pb (Zr, Ti)O₃ (PZT) system. The advantages of bismuth perovskites over PZT are environmentally more-friendly materials, a higher mechanical strength and Curie temperature. Most recently BiMgZrO₃-PbTiO₃ has been reported to be high temperature morphotropic phase boundary (MPB) piezoelectric with appreciably good ferroelectric and piezoelectric properties.Bismuth containing crystalline solutions [(BiMgZrO₃)_1−y-(BiFeO₃)_y]_x-(PbTiO₃)_1−x, (BMZ-BF-PT) have been synthesized by high temperature solid-state reaction technique. The crystalline symmetry varied with the composition, indicating good solid-state solubility of BMZ and BF with PT. X-ray diffraction (XRD) reveals that BMZ-BF-PT has a single-phase perovskite structure. The Morphotropic Phase Boundary (MPB) of BMZ-PT system lies in the region x = 0.55 to x = 0.6 which is supported by the transformation from tetragonal to rhombohedral phase. The SEM photographs reveal the uniform distribution of grains in the matrix. Variation of dielectric parameters with frequency (at room temperature) exhibit typical dielectric behavior for all compositions.     

Effects of intense plastic straining on the structure of barium,lead, and cadmium titanates

Under the action of intense plastic straining (IPS), barium titanate (BaTiO₃) exhibits a phase transition from the tetragonal to cubic structure, while lead titanate (PbTiO₃) shows a tendency to such a transformation. In cadmium titanate (CdTiO₃), the IPS induces a transition from the perovskite to ilmenite phase.     

Dielectric and piezoelectric studies of perovskite-tungsten bronze structured (1 − x)[0.5PMN-0.5PZT]-xPBBiN nanoceramic composites by high-energy mechanical activation technique

In this paper, phase development, dielectric and piezoelectric properties of nanocomposites consisting of perovskite structured PMN-PZT and tungsten bronze structured PBBiN synthesized via high energy mechanical activation technique were examined as a function of x in (1 ? x)(0.5PMN-0.5PZT)-xPBBiN with a stoichiometric formula as (1 ? x)[0.5Pb(Mg_0.33Nb_0.67)O₃-0.5Pb(Zr_0.53Ti_0.47)O₃]-x[Pb_0.59Ba_0.38Bi_0.02Nb₂O₆]. It was observed that the high-energy mechanical activation technique has greatly improved the reactivity of the precursors by reducing the phase formation temperatures and eliminating unwanted secondary phases and liquid phase sintering as x increased. Powder X-ray diffraction studies of the ternary system revealed the perovskite cubic (PMN-PZT) coexisted with tungsten bronze orthorhombic (PBBiN) phase. The average particle size ranged from 22 to 81 nm. A combination of both perovskite and tungsten bronze grains revealed intragranular and intergranular growth which accelerated densification and homogeneity in the nanocomposite. The dielectric (ε_RT = 2,248) and piezoelectric properties (d ₃₃ = 412 pC/N and k _p = 0.446) obtained were maximum at x = 0.4 which could be suitable for possible electromechanical and energy harvesting applications.     

Morphotropic phase boundary in the system Pb(ZrxTi1−x)O3

The room temperature phase boundary dividing the rhombohedral and tetragonal in the solid solution system lead zirconate titanate Pb(Zr_xTi_1?x)O₃ is examined carefully using an ultrahomogeneous synthesis technique. There is no evidence for a broad transition region of co-existing phases as understood earlier but a sharp boundary located at x = 0.510 ± 0.002.