Excess PbO Research Articles

Effect of excess PbO on microstructure and orientation of PZT(60/40) films

Lead zirconate titanate [PZT(60/40)] films were deposited by RF-magnetron sputtering using single oxide targets with various levels of excess PbO. The excess PbO in the film played an important role in the pyrochlore-to-perovskite transformation, nucleation and growth processes, orientation control, and crack formation. When 5% or 20% excess PbO was added to the target, pyrochlore phases were created and the films were severely cracked. However, the films had a perovskite structure without any pyrochlore phases when 10% or 15% excess PbO was added to the targets. More interestingly, the crystallographic orientation was strongly dependant on the excess PbO content. A film with a (111) preferred orientation was produced when 10% excess PbO was added to the target. On the other hand, a film with a (100) preferred orientation was deposited by the target with 15% excess PbO. The dielectric, ferroelectric and piezoelectric properties of these films with different orientations and microstructures were examined and correlated with the film structure.

Phase Formation, Microstructure and Phase Transition of Lead Barium Titanate Ceramics: Effect of PbO Content

Monophasic oxides of the formula, (Pb 0.975 Ba 0.025 )TiO 3 with excess PbO (0, 1, 3, 5 and 10 wt%) were prepared by a mixed oxide method. It was found that lead barium titanate powders indexed in a tetragonal structure. The impurity phases were detected in the calcined powders with ≥ 3 wt% of excess PbO. The impurity phases were not present in any ceramic samples. The c/a ratio was decreased with increasing of excess PbO. The average particle size and the average grain size of the PBT increased with increasing of PbO contents. The density can be improved by adding 1 wt% of excess PbO. The DSC results indicated that the Curie point shifted to higher temperature when the excess PbO was higher than 3 wt%.

Properties of (Pb0.90Ba0.10)ZrO3 Ceramics with Deficient and Excess PbO

The effects of excess PbO on the properties of perovskite (Pb0.90Ba0.10)ZrO3 (PBZ10) have been investigated. The PBZ10 ceramics were prepared by a conventional mixed oxide method. Excess PbO (−1.5, 1, 3, 5 and 10 wt%) was added together with starting materials to compensate for PbO loss from evaporation during calcination and sintering. The XRD results revealed that the fraction of the orthorhombic phase has effected by PbO content. The 3 wt% PbO excess sample exhibited the maximum value of relative permittivity at the Curie temperature, while the 1 wt% PbO excess sample showed maximum value of piezoelectric strain coefficient d 33 and electromechanical coupling factor k p .

The Role of Li2CO3 and PbO in the Low‐Temperature Sintering of Sr, K, Nb (SKN)‐Doped PZT

It is demonstrated that the use of ∼0.9 mol% Li2CO3 (LC) as a sintering aid for Sr, K, Nb modified Pb(Zr1−x,Tix)O3 (PZT) ceramics is effective only in the presence of excess PbO (∼2 mol%). It is shown that LC and PbO react to form the compound, Li2PbO3 (LPO) which has a melting temperature of ∼836°C. Using dilatometry, we were able to correlate shrinkage during heating of a green ceramic to the melting of the LPO. Consequently, complete densification and sizeable grain growth are achieved by solution‐precipitation of the ceramic through the liquid phase. Importantly, sintering is not particularly effective with such small additions of either LC or PbO alone. In confirmation of this model, the LPO compound was presynthesized and used as the only sintering aid in the same PZT composition. The densification behavior of this mixture compared well with the case of separate additions.

Dihydroxylation of alkenes using a Tp–osmium complex

The reaction of TpOs VI(N)(OH) 2 ( 1) [Tp = hydrotris(1-pyrazolyl)borate], m-chloroperbenzoic acid ( m-CPBA), and trans-stilbene in C 6H 6 at room temperature gives the diolate complex TpOs VI(N)( trans-O 2C 2H 2Ph 2) ( 2) and m-chlorobenzoic acid ( m-CBA). The trans configuration of the stilbene is retained in the diolate complex as shown in the crystal structure of 2. Complex 2 is hydrolyzed by 2 equivalents of aqueous HCl in CD 2Cl 2 to give rac-hydrobenzoin, the product of cis-dihydroxylation, and TpOs VI(N)Cl 2. cis-Stilbene, styrene, cyclohexene, trans-dimethyl fumarate, trans-methyl cinnamate, and trans-4-dimethylamino-4′-nitrostilbene are also converted to their corresponding free diol products by reaction with 1 and m-CPBA in CD 2Cl 2, and then aqueous HCl. In aqueous HBF 4, oxidation of the water-soluble olefin, 4-styrenesulfonic acid, by 1 is modestly catalytic (15 turnovers in 3 h) with excess PbO 2 as the oxidant. Under non-acidic conditions, the diolate complexes are inert and catalysis is precluded. Mechanistic experiments implicate an oxidizing osmium complex as an intermediate in these reactions.

Template-assisted synthesis of PbTiO 3 nanotubes

Nanotubes of ferroelectric lead titanate (PbTiO 3) have been made by a template-assisted method. An equimolar Pb–Ti sol was dropped onto porous alumina membranes and penetrated into the channels of the template. Single-phase PbTiO 3 perovskite nanotubes were obtained by annealing at 700 °C for 6 h. The nanotubes had diameters of 200–400 nm with a wall thickness of approximately 20 nm. Excess PbO or annealing in a Pb-containing atmosphere was not necessary in order to achieve single-phase PbTiO 3 nanotubes. The influence of the heating procedure and the sol concentration is discussed.

Investigation of the Pb Depletion in Single and Dual Pulsed Laser Deposited Epitaxial PZT Thin Films and Their Structural Characterization

AbstractWe have investigated the Pb depletion in laser ablated PZT (PbZr0.52Ti0.48O3) films through a systematic study of PZT target-laser interactions for both single laser and dual-laser ablation methods. The study includes films deposited from a stoichiometric and an excess PbO PZT targets. The films were deposited on single crystal SrTiO3[100] substrates at 550˚C with a background oxygen pressure of 500 mT. Single laser deposited films at a laser fluence of 5J/cm2 produced the highest Pb content while dual-laser ablated films where an excimer and a CO2 pulsed lasers were synchronized for ablation produced high Pb content for an excimer laser fluence of less than 2J/cm2. This enabled the growth of particulate-free PZT films with high Pb content. ICCD imaging of the plasma plumes showed variations in the expansion profiles at different laser fluencies that correlated well with the Pb content observed in the deposited films.

LOW SINTERING TEMPERATURE OF LEAD MAGNESIUM NIOBATE-LEAD TITANATE (0.9PMN–0.1PT) BY ADDING OXIDE ADDITIVES

This research work is aimed at lowering the sintering temperature of 0.9PMN–0.1PT ceramics by adding oxide additives. The oxides used for this purpose were Bi 2 O 3 and Li 2 CO 3 with various amounts, following the formula of xBi 2 O 3+y Li 2 CO 3, where x+y = 10 mol % and x = 1, 3, 5 and the mixed oxide additive powders were then added to the dried powder of 0.9PMN–0.1PT with 1 wt% concentration. An excess PbO content of approximately 3 wtadded to all compositions to compensate the lead loss. After that, the mixed powders were pressed into pellets and subsequently sintered to form the ceramic samples. The results showed that the sintering temperature of 0.9PMN–0.1PT ceramics could be lowered down from 1250°C to 900–1000°C by the addition of small amount of the oxide additives, where the optimum composition was found in the sample with x : y = 1 : 9 at sintering temperature of 1000°C. Moreover, the densification, dielectric and ferroelectric properties of this sample remain acceptable in particular uses, promising positive future for reduction of lead loss from electrical and electronic industries.

Effect of LaNiO 3 electrodes and lead oxide excess on chemical solution deposition derived Pb(Zr x,Ti 1 − x)O 3 films

The effects of LaNiO 3 (LNO) and Pt electrodes on the properties of Pb(Zr x ,Ti 1 − x )O 3 (PZT) films were compared. Both LNO and PZT were prepared by chemical solution deposition (CSD) methods. Specifically, the microstructure of LNO and its influence on the PZT properties were studied as a function of PbO excess. Conditions to minimize the Pyrochlore phase and porosity were found. Remnant polarization, coercive field and fatigue limit were improved in the PZT/LNO films relative to the PZT/Pt films. Additionally, the PZT crystallization temperature over LNO was 500 °C, about ~ 50 °C lower than over Pt. The crystallization temperature reported here is amongst the lowest values for CSD-based PZT films.

Microstructure of Compositionally Graded PZT films Grown by Pulsed Laser Deposition

Ferroelectric films with a composition gradient have attracted much attention because of their large polarization offset present in the hysteresis loops. Lead Zirconate Titanate (PZT) films were deposited on Pt/TiO2/SiO2/Si substrates by Pulsed Laser Deposition (PLD) technique, using a Nd:YAG laser (Surelite) with a source pulse wavelength of 1064 nm and duration of 5-7 ns delivering an energy of 320 mJ per pulse and a laser fluence energy about 20 J/cm2. The film growth is performed in O2 atmosphere (0,40 mbar) while the substrate is heated at 600°C by a quartz lamp. Starting from ceramic targets based on PZT compositions and containing 5% mol. of excess of PbO to compensate the lead evaporation during heat treatment, three films with different compositions Zr/Ti 55/45, 65/35 and 92/8, and two types of complex structures were produced. These complex structures are in the case of the up-graded structure (UpG), with PZT (92/8) at the bottom, PZT (65/35) on middle and PZT (55/45) on the top, and for down-graded (DoG) one, that order is reversed.

Microstructure–Property Relationships in Liquid Phase‐Sintered High‐Temperature Bismuth Scandium Oxide‐Lead Titanate Piezoceramics

High‐temperature piezoelectrics are necessary for aeronautic and aerospace applications. The principal challenge for the insertion of piezoelectric materials is their limitation for upper use temperature, which is due to low Curie temperature and increasing conductivity at high temperatures. We investigated processing, microstructure, and property relationships of (1−x)BiScO3−(x)PbTiO3 composition as a promising high‐temperature piezoelectric. The effects of excess PbO and Bi2O3 and their partitioning in grain boundaries were studied using impedance spectroscopy, ferroelectric, and piezoelectric measurement techniques. Excess Pb addition increased the grain‐boundary conduction and the grain‐boundary area resulting in ceramics with higher AC‐conductivity (tan δ=0.9 and 1.7 for 0 and 5 at.% excess Pb at 350°C and at 10 kHz) that were not resistive enough to pole. Excess Bi addition increased the resistivity (tan δ=0.9 and 0.1 for 0 and 5 at.% excess Pb at 350°C and at 10 kHz), improved poling, and increased the piezoelectric coefficient from 354 to 408 pC/N for 5 at.% excess Bi addition. Thus, excess Bi2O3 proved to be a successful liquid phase forming additive to improve the 0.37BiScO3–0.63PbTiO3 piezoceramics for high‐temperature applications, as a result of increased resistivity and enhanced piezoelectric activity.

Effects of Excess PbO and Zr/Ti Ratio on Microstructure and Electrical Properties of PZT Films

Lead zirconate titanate films with different Zr/Ti ratios were fabricated on a platinized silicon substrate using radio frequency magnetron sputtering. Crack‐free films with a rhombohedral, morphotropic phase boundary and tetragonal compositions were deposited using single oxide targets containing various amounts of excess PbO. When the films showed a (111) preferred orientation, there were no cracks, regardless of the phase, and their microstructures were similar to one another. As the Zr/Ti ratio was changed, the amount of excess PbO necessary for the stoichiometry of the films also changed. When they had a stoichiometric composition, the films had a small grain size and similar microstructures. Moreover, their structural stability increased when the grains had an equiaxed morphology. The ferroelectric and piezoelectric properties of the films were characterized and correlated with their phase and microstructure.

Effect of Excess PbO on Crystal Structure, Microstructure and Phase Transition of Lead Titanate Ceramics

In this work, we studied the effect of excess PbO on crystal structure, microstructure and phase transition of lead titanate (PT). PT was prepared via a mixed oxide method with various PbO levels (0, 1, 3 and 5 wt.%). The raw materials were calcined at 750 oC for 2 h and sintered at 1225 oC for 2 h. The characteristics of PT were analyzed by a X-ray diffractometer (XRD), scanning electron microscopy (SEM) and differential scanning calorimeter (DSC). It was found that calcined powders and sintered ceramics indexed in a tetragonal structure. For PT powders, the impurity phases of lead oxide (PbO) and lead dioxide (PbO2) were detected in 3 and 5 wt.% of excess PbO samples, but they were not detected in all sintered ceramic samples. The increase of excess PbO levels resulted in a decreased c/a ratio in both calcined powders and sintered ceramics. Average particle sizes increased from 0.64 to 4.24 µm when excess PbO levels increased from 0 to 5 wt.%. It was also clearly seen that the liquid phase of the sintering process was obtained in the PT calcined powders which had an excess of PbO. The DSC result indicated that the phase transition temperature, from a ferroelectric to a paraelectric phase with a high PbO content (5 wt.%), was higher than those with low PbO contents (0, 1 and 3 wt.%).

The Effect of Excess PbO on Crystal Structure and Microstructure of (Pb<sub>0.925</sub>Ba<sub>0.075</sub>)TiO<sub>3</sub> Ceramics

In this work, we studied the effect of excess PbO doping on lead barium titanate [(Pb0.925Ba0.075)TiO3; (PBT)] ceramic. PBT was prepared via a mixed oxide method with various PbO levels (-3, 0, 1, 3, 5 and 10 wt.%). The excess PbO was added to compensate the loss from evaporation during calcination and sintering at 800 oC and 1150 oC. It was found that lead barium titanate powders indexed in a tetragonal structure. Impurity phases of lead oxide (PbO), titanium oxide (TiO), and lead dioxide (PbO2) were detected in the calcined powders with higher than 1 wt% of excess PbO. The impurity phase was not obtained in any ceramic samples. The c/a ratios decreased with an increasing excess of PbO in both calcined powders and sintered pellets. The average particle size and the average grain size of the PBT increased with the increase of PbO. The shrinkage plots showed a maximum peak for the 1 wt.% sample which was also the most dense sample.

Processing and properties of 0.65Pb(Mg 1/3Nb 2/3)O 3–0.35PbTiO 3 thick films

We have investigated the processing of 0.65Pb(Mg 1/3Nb 2/3)O 3–0.35PbTiO 3 (PMN–PT) thick films on platinised alumina substrates. Nanosized PMN–PT powder with 2 mol% of excess PbO was prepared by high-energy milling and deposited on the substrate using screen-printing technology. The films were then sintered at 950 °C in a PbO-rich atmosphere. The influence of the sintering time and the amount of PbO-containing packing powder was studied and related to the structural, microstructural, dielectric and piezoelectric properties of the film. In order to obtain a homogeneous and dense thick film without any secondary phase, the PMN–PT films had to be sintered in the presence of a PbO-based liquid phase that had to be completely removed from the thick film during the final stage of the sintering. Under optimal sintering conditions we obtained a room temperature relative dielectric permittivity of 3600, dielectric losses of 0.036, a T m of 174 °C, a permittivity at the T m of 21,000 and a d 33 of 140 pC/N.

Homogeneous templated grain growth of 0.65Pb(Mg 1/3Nb 2/3)O 3-0.35PbTiO 3 from nanocrystalline powders obtained by mechanochemical activation

The feasibility of a novel homogeneous templated grain growth approach for the processing of 0.65Pb(Mg 1/3Nb 2/3)O 3-0.35PbTiO 3 ceramics is studied. Novelty rests on the use of a nanocrystalline powder synthesized by mechanochemical activation for the matrix, and also for obtaining the templates via conventional sintering. Templates are (1 0 0) faceted cube-shaped microcrystals with an average size of 12 μm. The role of processing parameters such as the presence of PbO excess, and a hot-pressing step previous to the final thermal treatment is studied. Extensive growth of the templates and nearly full densification are demonstrated. The approach used here involves only conventional ceramic technology from a single source powder, and can be used as a means of obtaining larger crystals.

Structural evolution of PZTN thin films produced by pulsed laser ablation deposition

The study of highly oriented Nb-doped PZT thin films deposited by laser ablation on n-type (111) Si substrates is reported. Sintered ceramics based on the nominal composition Pb 0.995(Zr 0.65Ti 0.35) 0.99Nb 0.01O 3 (PZTN) with an excess of PbO were used as targets. The films were deposited using the 3rd harmonic (355 nm) of a pulsed Nd:YAG laser (7 ns pulse duration) with 7 J/cm 2 fluence, at different oxygen pressures (from 10 −1 to 10 −4 mbar) and at a vacuum of 10 −6 mbar. The substrate temperature was varied in the range of 500–600 °C. In optimized conditions, the as-deposited PZT-based films show perovskite structure oriented along the (110) direction with minor impurities (PbO), as revealed from X-ray diffraction spectra. Further, microstructural analysis of the as-grown including chemical composition is also presented. The relationship between composition of the target, deposition conditions and film properties are then discussed.

Characterization of Nb-doped PZT (65/35/1) ferroelectric thin films deposited by pulsed laser ablation

Using ceramic targets prepared by conventional way, based on the composition Pb 0.995(Zr 0.65Ti 0.35) 0.99Nb 0.01O 3 + 4% mole PbO excess (PZTN), several ferroelectric films were deposited by pulsed laser ablation (PLA) technique on Pt (111) coated Si and MgO (100) substrates, using XeCl (308 nm) excimer laser. X-ray diffraction is used to characterize the produced perovskite phase (rhombohedral phase) as well as to evaluate the secondary phases and to describe the structural changes during annealing. The optical characteristics are measured in the UV–vis–near IR region. Also, ferroelectric hysteresis behaviour has been characterized by CV measurements.

The effect of high energy mechanochemical processing on the microstructure, piezoelectric,ferroelectric and mechanical properties of PLZT ceramics

Lead lanthanum zirconate titanate (PLZT) ceramics were synthesized using a high energymechanochemical processing technique, using tungsten carbide grinding vials and balls.The ceramic powders were prepared using the constituent oxide powders, whichwere subjected to high energy milling, without the use of any excess PbO in thestarting composition. TEM studies revealed the formation of very fine particlesof the order of 30 nm, due to the milling effect. Highly dense ceramics could beprepared via sintering which resulted in ultra-high strains in these piezoelectricsamples of up to 0.25%, a value which has not been reported hitherto by any otherknown process. The effect of the reduction in particle size on the microstructure,mechanical and electrical properties of PLZT ceramics were studied and are discussedherein.

Antiferroelectric-ferroelectric phase transitions in Pb1−xBaxZrO3 ceramics: Effect of PbO content

The irreversibility of the antiferroelectric (AFE) to FE phase transition in Pb1−xBaxZrO3, x=0.75–0.1, compositions is shown to be a consequence of lattice vacancies arising from PbO evaporation during ceramic processing. Previously, the absence of a FE→AFE cooling transition was thought to be due to the transformational strain and the fragmentation of ferroelectric domains. Appropriate compensating levels of excess PbO added to starting powders generate the FE→AFE transition. For lower levels of Ba2+ substitution, x=0.05, the transition is reversible in noncompensated samples, but PbO compensation raises the FE→AFE transition temperature by ∼25°C.