Excess PbO Research Articles

Tuning Nb Solubility, Electrical Properties, and Imprint through PbO Stoichiometry in PZT Films.

Lead zirconate titanate (PZT) films with high Nb concentrations (6-13 mol%) were grown by chemical solution deposition. In concentrations up to 8 mol% Nb, the films self-compensate the stoichiometry; single phase films were grown from precursor solutions with 10 mol% PbO excess. Higher Nb concentrations induced multi-phase films unless the amount of excess PbO in the precursor solution was reduced. Phase pure perovskite films were grown with 13 mol% excess Nb with the addition of 6 mol% PbO. Charge compensation was achieved by creating lead vacancies when decreasing excess PbO level; using Kroger-Vink notation, NbTi• are ionically compensated by VPb″ to maintain charge neutrality in heavily Nb-doped PZT films. With Nb doping, films showed suppressed {100} orientation, the Curie temperature decreased, and the maximum in the relative permittivity at the phase transition broadened. The dielectric and piezoelectric properties were dramatically degraded due to increased quantity of the non-polar pyrochlore phase in multi-phase films; εr reduced from 1360 ± 8 to 940 ± 6, and the remanent d33,f value decreased from 112 to 42 pm/V when increasing the Nb concentration from 6 to 13 mol%. Property deterioration was corrected by decreasing the PbO level to 6 mol%; phase pure perovskite films were attained. εr and the remanent d33,f increased to 1330 ± 9 and 106 ± 4 pm/V, respectively. There was no discernable difference in the level of self-imprint in phase pure PZT films with Nb doping. However, the magnitude of the internal field after thermal poling at 150 °C increased significantly; the level of imprint was 30 kV/cm and 11.5 kV/cm in phase pure 6 mol% and 13 mol% Nb-doped films, respectively. The absence of mobile VO••, coupled with the immobile VPb″ in 13 mol% Nb-doped PZT films, leads to lower internal field formation upon thermal poling. For 6 mol% Nb-doped PZT films, the internal field formation was primarily governed by (1) the alignment of (VPb″-VO•• )x and (2) the injection and subsequent electron trapping by Ti4+. For 13 mol% Nb-doped PZT films, hole migration between VPb″ controlled internal field formation upon thermal poling.

Optimisation of the Zr:Ti ratio in bulk lead zirconate titanate for templated grain growth using BaTiO3 seeds

Presented here is a proof of concept demonstration of the templated grain growth (TGG) process for the development of [001]c fibre-textured Pb(ZrxTi1-x)O3 (PZT) ceramics. BaTiO3 platelets (5 and 10 vol.%) were selected to seed growth of highly oriented PZT grains resulting in texture fractions as high as 94%. The TGG process in PZT was observed to be critically dependent upon the addition of excess PbO liquid phase and may be driven by BaTiO3 dissolution into the matrix. Solid solution incorporation of BaTiO3 during sintering resulted in a structural shift away from the PZT morphotropic phase boundary (MPB) and a decrease in Curie temperature (TC) by ~ 40 °C which still exceeded > 300 °C. Modification of the Zr:Ti ratio in untextured ceramic analogues was explored as a strategy to tailor dielectric, ferroelectric, and electromechanical properties. An initial PZT matrix composition of Pb(Zr0.56Ti0.44)O3 resulted in a final bulk Pb0.947Ba0.053(Zr0.531Ti0.469)O3 ceramic having MPB-like properties of d33 = 453 pC/N, tan δ = 0.017, TC = 340 °C, and Ec = 9.3 kV/cm, which was observed to be similar to commercial ‘soft’ PZT-5A1.

Giant piezoelectric properties of the [110]-oriented PZT-5H single crystals grown by solid state crystal growth

An ultrahigh piezoelectric performance (d33 ∼ 1800 pC N−1 and ∼ 2400 pm V−1 at 3 kV cm−1, k33 ∼ 87%) is achieved in the [110]-oriented PZT-5H single crystals grown using the solid state crystal growth method with excess PbO addition.

The influence of PbO excess in the charge on the optical transmission of Pb2MoO5 crystals

The single crystals of acousto-optic Pb2MoO5 were grown by the Czochralski technique from a charge of stoichiometric composition and with an excess of lead oxide. Optical transmission spectra of these crystals were measured in the visible wavelength range. The effect of the heat treatment in air and in vacuum was considered. Changes in the valence state of a part of Mo6+ ions to Mo5+ and possible microinclusions of foreign phases are supposed to be responsible for the decrease in the optical transmission of crystals obtained from the charge with PbO excess.

Pulsed Lased Deposition of Single-Crystalline (001) Oriented Pb(Zr0.5T0.5)O3 Thin Film on PrScO3 Substrate

High quality thin films are important for domain engineering applications such as on-volatile memory applications. Single crystalline (001) oriented Pb (Zr0.5T0.5)O3 thin films have been grown by pulsed laser deposition on PrScO3 with strontium ruthenate (SRO) electrodes. Thin films were prepared from PZT ceramic targets with 15% excess PbO to compensate for lead loss at high deposition temperature. Layer by layer/step flow growth mode observed on AFM images has been realised by using a single terminated PrScO3 substrate as well as optimized deposition parameters. XRD measurements have confirmed the highly (001) oriented tetragonal symmetry. Furthermore, analysis conducted using piezoresponse force microscopy has shown that the thin films are monodomain with spontaneous ferroelectric polarization preferentially pointing upwards, i.e., away from the substrate. The absence of ferroelastic domains and the observed single ferroelectric domain structure are the results of both relatively small compressive misfit strain as well as favourable electrical boundary conditions.
 Keywords: PZT; Pulsed Laser Deposition; Epitax; Thin film

Defects minimisation promoted by lead-volatility in (Pb,La)(Zr,Ti)O3 ferroelectric ceramics

La-modified PbZrTiO3 ferroelectric ceramics with Pb0.92La0.08(Zr0.686Ti0.294)O3 nominal composition were obtained via the conventional solid-state reaction method, by considering different PbO excess (5, 10 and 15 mol %). The structural properties, were investigated from X-ray diffraction (XRD) and Raman Spectroscopy techniques, both at room temperature. Results confirmed the formation of the perovskite structure with rhombohedral symmetry (R3m space-group) for all the samples. The dielectric properties were also investigated, from the temperature dependence of the dielectric response, and results revealed the characteristic response of ferroelectric materials for all the compositions. The obtained very broad peak in the maximum dielectric permittivity, around Tm (~107°C), suggests the diffuse character of the ferroelectric-paraelectric phase transition.

Evaluation of the effect of excess PbO on piezoelectric properties of high Zr -PZT ceramics

Ferroelectric Pb0.99+x(Zr0.95Ti0.05)0.98Nb0.02O3+y, where x = 0.01–0.04, y = 0.01–0.04 ceramics were fabricated using pressureless sintering with excess PbO addition (to counter the volatilization effect of PbO) and ferroelectric, piezoelectric and structural properties were studied. X-ray diffraction studies confirmed formation of single phase with perovskite structure. Addition of excess PbO contributed to monotonic increase in grain size from 5 to 9 µm. The remnant polarization (Pr) demonstrated a similar rise from 17 to 29 pC/cm2. The electrical fatigue test demonstrated minimal change in the Pr values up to 106 cycles. The P-E loops showed saturated ferroelectric hysteresis even up to substantially high temperature of 240 °C. The optimal properties were obtained for x = 0.03, which were Pr = 29 pC/cm2, εr = 290, and d33 = 72 pC/N.

Influence of excessive Pb and sintering temperature on the structure and properties of 0.39BS-0.61PT ceramics

Recently, (1-x)BiScTiO3–xPbTiO3 (BS–xPT) ceramics have attracted extensive research attention owing to their higher Curie temperature and better piezoelectric properties than Pb(Zr,Ti)O3 (PZT) ceramics. The piezoelectric properties of PT-based ceramics are usually improved by adding excessive Pb, which compensates the PbO volatilization during sintering. This study investigates the phase structures and electrical properties of 0.39BS–0.61PT ceramics after introducing 1 wt% excessive PbO and modulating the sintering temperature. Unexpectedly, adding 1 wt% excessive PbO degraded the piezoelectric properties relative to those of 0.39BS–0.61PT ceramics. Above a critical sintering temperature (1150 °C), the rhombohedral phase structure of ceramics changed to a morphotropic phase boundary, resulting in an obvious increase in piezoelectric properties. Excellent electrical properties (piezoelectric constant d33 = 417 pC/N, electromechanical property kp = 53%, dielectric loss tanδ = 0.02) were exhibited by 0.39BS–0.61PT ceramics. All ceramics exhibited a high Curie temperature (Tc ≈ 415 °C) and superior piezoelectric stability from room temperature to 330 °C, suggesting their applicability under high–temperature conditions. Our experimental results provide a new approach for designing materials with the desired electrical properties for low-lead BS–PT ceramics. Keywords: BS–PT ceramics, Electrical properties, Phase structure, Excessive PbO.

Synthesis, optical, structural, and radiation transmission properties of PbO/Bi2O3/B2O3/Fe2O3 glasses: An experimental and in silico study

In this paper, a new glass combination containing PbO, Bi2O3, B2O3, and Fe2O3 has been synthesized, characterized, and studied in details for advanced optical and radiation shielding applications. The PbO excess was in the step of 10% at the expense of (Bi2O3+B2O3). The physical and optical parameters were experimentally measured for each prepared glass sample.The structure characterization of the glass specimens was performed by using both FTIR and XRD. Moreover, EPR spectra were studied to give a full understanding about the valence state and interaction of paramagnetic ions. Additionally, Monte Carlo method was utilized to design the simulation setup for studying the radiation propagation through the prepared samples. The obtained results indicate thatthe optical band gap values were found to be high with excess of PbO content. The EPR spectra have shown a high intense resonance signal at g ≈ 4.2 and mild intense signal located at g ≈ 2.1. The magnitudes of linear attenuation coefficients for the glasses at different energies shows that maximum (minimum) value of 290.39 (0.158), 322.67 (0.168), 367.13 (0.184), 431.04 (0.207), 502.32 (0.231), and 574.34 (0.0257) cm−1 was obtained for PBBF-0 – PBBF-50. This investigation lays the foundation for using the prepared glass system as a new candidate in advanced optical and shielding applications.

Influence of the PbO-excess on the structural, microstructural and ferroelectric properties of PLZT ceramics

The physical properties of lead lanthanum zirconate titanate (PLZT) ceramics have been investigated as a function of a PbO excess from 0 to 20 mol% in samples of Pb0.94La0.06(Zr0.6895Ti0.2955)O3 (composition that reveals the best performance for piezoelectric applications for materials with rhombohedral symmetry). Results are presented in a compressive way in the frame of an overview on PLZT. Structural, microstructural and ferroelectric properties were investigated as a function of the PbO content. The X-ray diffraction results confirmed the formation of the perovskite structure for all the cases. However, the presence of the Pb2O3 secondary phase has been observed for the sample containing 15 mol% PbO excess. Raman spectroscopy studies revealed a strong influence of the PbO content on the active modes shifts. The ferroelectric properties have shown a decrease of both remnant (PR) and saturation (PS) polarizations for compositions up to 10 mol% PbO, whereas an increase of PR and PS was observed for the higher PbO content samples. Results reveal the effect of the PbO excess on the long-range order interactions for the studied system.

A novel vacuum/oxygen hot press sintering approach for the fabrication of transparent PLZT (7.4/70/30) ceramics

Transparent Lanthanum-modified lead zirconate titanate ceramics (PLZT 7.4/70/30) with low content of excess lead oxide (PbO) were successfully prepared by a novel vacuum/oxygen hot press sintering process. The phase structure, microstructure, electrical properties and electro-optic scattering performance of PLZT ceramics as a function of excess PbO in the starting powders have been studied and analyzed. As a result, these ceramics exhibited an ultra-high optical transmittance (>69.4% at 1064 nm; thickness 1 mm) from visible to near-infrared wavelength. Herein, we significantly reduce the use of PbO as an auxiliary agent for sintering. This puts forward a good route to meet the objectives of environmental protection and sustainable development.

Inkjet-printing-derived lead-zirconate-titanate-based thick films for printed electronics

We have investigated the processing of lead-zirconate-titanate-based thick films by inkjet printing Pb(Zr0.53Ti0.47)0.98Nb0.02O3 with a 6 mol% excess of PbO nanosized powder dispersed in water. Different waveforms were employed to determine the optimum size and shape of the drops. A uniform, defect-free pattern with dimensions of 4 mm × 4 mm can be printed using 20 V and a drop spacing of 20 μm. The inkjet-printed films were heated to 400 °C to remove the organics and subsequently sintered at 750 and 850 °C. The correlations between the density, grain size and electromechanical properties of the thick films and bulk ceramics are qualitatively discussed. A thickness coupling factor of 46% was obtained for a 15-μm-thick film sintered at low temperature of 850 °C, which is comparable to the value of the bulk ceramic with an identical nominal chemical composition. Our results are important for the economic and environmental-benign printing of piezoelectric materials applicable in variety of electronic devices, such as sensors, actuators, transformers, piezoelectric energy harvesters and transducers.

Realization of 1 μm thick, crack-free and smooth PMN-PT film in the MPB through PLD: A comprehensive study

This paper presents a comprehensive study on the various hurdles and solutions in the realization of phase pure, pinhole-free and crack-free, 0.65PMN-0.35PT/LSCO/Pt/TiO2/SiO2/Si heterostructures using pulsed laser deposition. A few major inquiries were i) effect of excess PbO in the target, ii) modulation of deposition and annealing temperatures for the growth of LSCO buffer layer, iii) thickness of the buffer layer iv) effect of the flow of oxygen in the chamber during and after deposition and v) the annealing conditions; on the phase formation, morphology and leakage response demonstrated by the films. Ferroelectric response parameters viz. Psat = 47.7 μC/cm2, Pr = 20.03 μC/cm2, EC = 62.03 kV/cm and absolute area = 21460 units attest the quality of the grown film.

Sol-Gel Synthesis and Piezoelectric and Structural Properties of Zr –rich PZT Nanoparticles

Lead zirconate titanate (PZT) nanopowders with spherical-shaped morphology, perovskite structure and an average size of 20 nm were successfully synthesized. The prepared PZT nanopowders were characterized by differential thermal analysis (DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), Energy dispersive X-ray (EDS) and Transmission electron microscopy (TEM) technique. Single-phase perovskite PZT nanopowders were obtained after heat treatment at a temperature of 700 °C. The effect of calcination temperature on crystal structure of PZT nanopowders has been discussed. Dielectric relaxation of the ferroelectric ceramics could originate from the alternations of the elastic and electric behavior and the movement of the domain walls at high-frequency regions. To determine a piezoelectric property of ceramics, resonant vibration spectrum of samples was measured at room temperature. A relative density of 7.53 g/cm3 was achieved at a sintering temperature of 1150 °C, which is close to the theoretical density (~95%). At higher temperature sint, the density of ceramic samples strongly decreases which can be attributed to the evaporation of excess PbO. The optimum values of piezoelectric constant, electromechanical quality factor and a mechanical quality factor are obtained at Sintering temperature 1150 °C: d33=64 pC/N, Ƙp=0.41 and Qm=34.3.

Structural, piezoelectric, and dielectric properties of PZT-based ceramics without excess lead oxide

A number of previous research have been done on the excess PbO to improve the material properties of PZT-based ceramics. This study takes a step further by studying the consequences of controlled addition of PbO on the structural, piezoelectric, and dielectric properties of Pb(Zr1-xTix)O3 ceramics (PZT-based ceramics). In order to draw qualitative comparisons between their material properties, pure or undoped PZT [Pb(Zr0.52Ti0.48)O3] and doped PZTs (PSZT [Pb0.95Sr0.05(Zr0.52Ti0.48)O3], PLZT [Pb0.98La0.02(Zr0.52Ti0.48)O3], and PLSZT [Pb0.93La0.02Sr0.05(Zr0.52Ti0.48)O3]) were studied. The compositions were prepared through high-energy ball milling in a way to avoid calcination using controlled addition of PbO. After milling, pellets were formed from the mixtures, which were then sintered at 1150 °C. The phase analysis of the sintered mixtures using XRD technique revealed the formation of a single perovskite phase in all the developed ceramics. All the undoped and doped ceramics have relative density of > 90%. La-doped PZT had the best piezoelectric properties with d33 of 372 pC/N and kp of 0.510; in addition, better dielectric properties, i.e., ɛr of 1269 and tan δ of 0.050, were found. This good performance of the La-doped PZT is related to its high density (7.6 g/cm3) and low porosity (0.154), which was clearly observed in its microstructure.

PZT/PZT and PZT/BiT Composite Piezo-Sensors in Aerospace SHM Applications: Photochemical Metal Organic + Infiltration Deposition and Characterization.

The composition of fine-ground lead zirconate-titanate powder Pb(Zr0.52Ti0.48)O3, suspended in PZT and bismuth titanate (BiT) solutions, is deposited on the curved surface of IN718 and IN738 nickel-based supper alloy substrates up to 100 µm thickness. Photochemical metal organic and infiltration techniques are implemented to produce smooth, semi-dense, and crack-free random orientated thick piezoelectric films as piezo-sensors, free of any dopants or thickening polymers. Every single layer of the deposited films is heated at 200 °C with 10 wt.% excess PbO, irradiated by ultraviolet lamp (365 nm, 6 watt) for 10 min, pyrolyzed at 400 °C, and subsequently annealed at 700 °C for one hour. This process is repeated successively until reaching the desired thickness. Au and Pt thin films are deposited as the bottom and top electrodes using evaporation and sputtering methods, respectively. PZT/PZT and PZT/BiT composite films are then characterized and compared to similar PZT and BiT thick films deposited on the similar substrates. The effect of the composition and deposition process is also investigated on the crystalline phase development and microstructure morphology as well as the dielectric, ferroelectric, and piezoelectric properties of piezo-films. The maximum remnant polarization of Pr = 22.37 ± 0.01, 30.01 ± 0.01 µC/cm2, the permittivity of εr = 298 ± 3, 566 ± 5, and piezoelectric charge coefficient of d33 = 126, 148 m/V were measured versus the minimum coercive field of Ec = 50, 20 kV/cm for the PZT/PZT and PZT/BiT thick films, respectively. The thick film piezo-sensors are developed to be potentially used at frequency bandwidth of 1–5 MHz for rotary structural health monitoring and also in other industrial or medical applications as a transceiver.

Effects of dopants on the microstructure and phase-purity control in PMN-PT ceramics

The effects of Pb2+, Ba2+, La3+, Y3+ and Gd3+ dopants on the densification and microstructure evolution of PMN-PT ceramics are investigated. The ceramics were reactively-sintered between 850 and 1250 °C in oxygen atmosphere. After sintering, all ceramics reached a relative density greater than 98%. XRD and SEM results revealed that lanthanum doping produces pure perovskite phase with unimodal rounded grains whereas other dopants yield microstructures with faceted grains due to the liquid phase formed in the intermediate stage. The mechanism for the observed differences in phase and morphology is also explored. The slower densification rate of La-doped samples helps maintain an open porosity network and favors the outgassing of the initial excess of PbO. The delayed densification contributes to the formation of pure perovskite at a temperature of 850 °C. Preferential A-site occupancy of La3+ lowers the oxygen vacancy concentration which suppresses grain growth.

The Acoustic Impedance and other Properties of (1-3) Piezoceramics Polymer Composite

The work is focused on an attempt to develop a route for the fabrication of piezoceamic-polymer composites having (1-3) type connectivity. The process included the extrusion of rods of diameter approximately 200 mm. A commercial piezoelectric, PC-5 was modified by addition of a lithium/bismuth based glass former together with excess PbO to lower the sintering temperature to about 1000 °C. The fast firing sintering was employed. The rods were assembled and impregnated with an epoxy resin to form 1-3 composites containing approximately 50 and 20 vol% piezoceramic. The measurement values showed that, the piezoelectric constant, d33= 232 pCN-1and 215 pCN-1, thickness electromechanical coupling coefficient, kt= 0.51 and 0.5 and the mechanical quality factor, Qm= 14 and 5 for the composites containg PZT rods at 50 vol% and 20 vol% respectively. Their acoustic impedances were 5.1 and 3.6 for the 50 vol% and 20 vol% of PZT rods respectively. The results show that with lower volume% of PZT could result in lower acoustic impedance which can be further improved for biomedical imaging and hydrophone applications.

Giant electrocaloric effect of free-standing Pb0.85La0.1(Zr0.65Ti0.35)O3 thick films fabricated by the self-lift-off screen printing method

Free-standing Pb0.85La0.1(Zr0.65Ti0.35)O3 (PLZT) ceramic thick films have been prepared via a facile and low-cost self-separating screen printing method for electrocaloric cooling, and the relation among the fabrication processes, phase composition, microstructure, dielectric characteristics, ferroelectric properties and electrocaloric effect (ECE) has been systematically investigated. Compared to the conventional ceramic thick films supported by substrates, the free-standing feature enables the EC cooling of the free-standing PLZT thick films to be fully used for cooling down different thermal loads rather than be futilely absorbed by the substrates. Furthermore, without the mechanical restriction of the substrates, the free-standing PLZT thick films can freely shrink during the high-temperature densification process, leading to their high density and favorable microstructures. Additionally, by introducing an adequate amount of excess PbO, the pyrochlore phase can be removed from the samples to yield high-purity perovskite PLZTs. With the comprehensive improvement in phase composition, microstructure and the elimination of mechanical strain between the active materials and substrates, the free-standing PLZT thick films exhibited an optimized ECE including changes of temperature and entropy of 1.95°C and 2.09Jkg−1K−1, which are almost 3 times that of the samples deposited on the Al2O3 substrates without excess PbO. This work would contribute to the development of ferroelectric ceramics, especially thick films, for practical EC cooling.

High electrocaloric effect in hot‐pressed Pb0.85La0.1(Zr0.65Ti0.35)O3 ceramics with a wide operating temperature range

AbstractThe temperature stability of the electrocaloric effect (ECE) in relaxor ferroelectric Pb0.85La0.1(Zr0.65Ti0.35)O3 (PLZT) prepared by the hot‐press sintering method has been investigated. Compared to the PLZTs prepared via the conventional sintering process, the hot‐pressed PLZTs exhibit larger ECE and superior temperature stability. The hot‐pressed sample with an appropriate content of excess PbO presents a high ΔT of 2.4°C and ΔS of 2.3 J kg−1·K−1, both of which are 30% greater than those of the conventionally sintered samples measured at 100 kV·cm−1. More importantly, the hot‐pressed specimens display great stable electrical properties, including the dielectric breakdown strength and electrical resistivity in the temperature range from 0°C to 100°C, whose ECE instability, especially, is only one‐half that of the samples prepared by the conventional solid‐state method. In addition, the ECE and its stability of the hot‐pressed sample can be further enhanced by increasing the operating electric field to a relatively high level of 200 kV·cm−1. This work demonstrates hot‐press sintering is an effective method to fabricate ferroelectric ceramics with high ECE as well as desirable temperature stability.