Lead Zinc Niobate Research Articles

Effects of Pb(Zn1∕3Nb2∕3)O3 addition and postannealing temperature on the electrical properties of Pb(ZrxTi1−x)O3 thick films prepared by aerosol deposition method

Effects of the lead zinc niobate (PZN) addition and postannealing temperature on the electrical properties of the lead zirconate titanate (PZT) films were observed to improve electrical properties of the PZT film. The PZN content was varied from 0% to 40%, and the postannealing temperature was varied from 500to900°C. The as-deposited film had a fairly dense microstructure without any cracking and showed a single perovskite phase formed with nanosized grains. Meanwhile, rapid grain growth was observed when the postannealing temperature was increased from 700to900°C. The PZN-added PZT film showed poorer electrical properties than the pure PZT film did when the films were annealed at 700°C but higher remnant polarization, dielectric constant, and piezoelectric response when the films were annealed at 900°C. Remnant polarization value, relative dielectric constant, and piezoelectric constant of the 20% PZN-added PZT films annealed at 900°C were 50.0μC∕cm2, 1643, and 200pC∕N, respectively, which are values sufficiently high to be comparable with the bulk specimen sintered at 1200°C.

High-permittivity and low-loss dielectric tunable pyrochlore thin films deposited by radio frequency magnetron sputtering from a lead zinc niobate target

Since Bi 2O 3–ZnO–Nb 2O 5 (BZN) pyrochlore thin films have been introduced as a tunable dielectric, the substitution of Bi with Pb could be a reasonable choice. The PbO–ZnO–Nb 2O 5 (PZN) cubic pyrochlore thin films were produced by radio frequency sputtering, and their dielectric properties, in terms of tunability, were measured. Up to 33.4% of tunability and comparable K factors with BZN films were obtained. The effects of film crystallization, along with substrate heating and post-annealing on the dielectric properties, were similar to those of BZN. However, strong texturing developed in the PbO–ZnO–Nb 2O 5 (PZN) films deposited at a high substrate temperature, which caused degradation of the loss tangent and K factor.

Fabrication of Porous PZT–PZN Piezoelectric Ceramics With High Hydrostatic Figure of Merits Using Camphene‐Based Freeze Casting

Porous lead zirconate titanate–lead zinc niobate (PZT–PZN) piezoelectric ceramics with interconnected pore channels were fabricated using the camphene‐based freeze‐casting method. In this method, warm PZT–PZN/camphene slurries with various solid loadings (10, 15, 20, and 25 vol%) were prepared by ball milling at 60°C and then cast into molds at 20°C, resulting in the formation of solidified green bodies comprised of three‐dimensionally interconnected camphene dendrite networks and concentrated ceramic particle walls. After the removal of the frozen camphene via sublimation, the samples were sintered at 1200°C for 2 h. All of the fabricated samples showed highly porous structures, consisting of fully dense PZT–PZN walls without defects, such as cracks or pores. As the initial solid loading was decreased from 25 to 10 vol%, the porosity was linearly increased from 50% to 82%. This increase in the porosity led to a reduction in the permittivity, a moderate decline in the d33 value, and a rapid decline in the d31 value, which endowed the porous samples with a high hydrostatic figure of merit (HFOM). The highest HFOM value of 35650 × 10−15 Pa−1 was achieved for the sample with a porosity of 82%, as well as ɛ33=284, dh=298 pC/N, and gh=118 × 10−3 V·(m·Pa)−1.

Electrical Properties of Lead Zinc Niobate - Lead Zirconate Titanate Thick Films Formed by Aerosol Deposition Process

Lead zinc niobate (PZN) added lead zirconate titanate (PZT) thick films with thickness of 5~10 μm were fabricated on silicon and sapphire substrates using aerosol deposition method. The contents of PZN were varied from 0, 20 and 40 %. The as deposited film had fairly dense microstructure without any crack, and showed only a perovskite single phase formed with nano-sized grains. The as-deposited films on silicon were annealed at temperatures of 700oC, and the films deposited on sapphire were annealed at 900oC in the electrical furnace. The effects of PZN addition on the microstructural evolution were observed using FE-SEM and HR-TEM, and dielectric and ferroelectric properties of the films were characterized using impedance analyzer and Sawyer-Tower circuit, respectively. The PZN added PZT film showed poor electrical properties than pure PZT film when the films were coated on silicon substrate and annealed at 700oC, on the other hand, the PZN added PZT film showed higher remanent polarization and dielectric constant values then pure PZT film when the films were coated on sapphire and annealed at 900oC. The ferroelectric and dielectric characteristics of 20% PZN added PZT films annealed at 900oC were comparable with the values obtained from bulk ceramic specimen with same composition sintered at 1200oC.

Low-voltage and high-tunability interdigital capacitors employing lead zinc niobate thin films

Employing high-tunability PbO–ZnO–Nb2O5 thin film dielectrics, low-voltage and high-tunability interdigital capacitors (IDCs) were implemented on a silicon substrate. In order to reduce the bias voltage of the IDC and increase its tunability, its electrodes were fully embedded into the thin film dielectrics to confine fringing electric fields within them. At 4V, the tunability of the IDCs was analyzed in terms of the electrode width and spacing by measuring reflection coefficients at 1GHz. The fabricated IDC with width and spacing of 1.5 and 1.8μm, respectively, achieved tunability of 26% and a Q factor of 10 at 5.5V.

Stress dependence of the polarized Raman spectrum of polycrystalline lead zirconate titanate

The stress dependence of the Raman spectrum of a relaxor-based polycrystalline ferroelectric lead zirconate titanate–lead nickel niobate–lead zinc niobate (PZT–PNN–PZN) has been investigated using polarized Raman microprobe spectroscopy. Emphasis has been placed on explicitly working out the second harmonic equations that relate Raman intensities to the angle between the laser polarization direction and selected crystalline axes. Based on these assessments, the effect under polarized light of crystal orientation on the intensity of selected Raman modes has been rationalized and the obtained experimental data interpreted. Raman spectra were collected with both parallel and cross polarization filters and their dependence on stress calibrated with loading the PZT–PNN–PZN samples in a four-point flexural jig. The use of polarized light allowed us to clarify the effect of domain orientation on the Raman spectrum of PZT–PNN–PZN and to perform precise calibrations of the stress dependence of the A1(TO4) Raman mode, independent of domain orientation in both poled and unpoled PZT–PNN–PZN samples. This study demonstrates the feasibility of microscopic stress (in addition to local domain orientation) evaluations in PZT materials using a polarized Raman microprobe.

Low‐Temperature Sintering of Lead Zinc Niobate–Lead Zirconate Titanate Ceramics Using Nano‐Sized Powder Prepared by the Stirred Media Milling Process

Lead zinc niobate–lead zirconate titanate (PZN–PZT) nano‐sized powders with a diameter of ∼35 nm were fabricated by a high‐energy stirred media mill using 50 μm diameter zirconia beads as the milling media at a rotation speed of 4000 rpm for 1 h. The sintering temperature of PZN–PZT was greatly reduced, and a fully densified bulk body was obtained at only 750°C when stirred media milled nanopowder was used. The control of evaporation of lead oxide was very important to obtain high electrical properties due to the increased surface area of nano‐sized powders. The ferroelectric hysteresis, piezoelectric d33 coefficient, and dielectric properties of sintered ceramics using nanopowder were measured and compared with the values obtained from a sintered specimen using conventional milled powders. Remanent polarization, d33 coefficient, and relative dielectric constant of 750°C sintered stirred media milled powders containing 2% of excess PbO and 1% of 4PbO–B2O3 liquid phase were 10.3 μC/cm2, 277 pC/N, and 1310, respectively.

The improvement in dielectric and ferroelectric performance of PZT–PZN ceramics by thermal treatment

Abstract Pyrochlore-free lead zirconate titanate – lead zinc niobate ceramics have been systematically investigated in the as-sintered condition as well as after annealing. The ceramics were characterized by dielectric spectroscopy and Sawyer–Tower polarization (P–E) measurements. The powders of Pb[(Zr1/2Ti1/2)(1−x)–(Zn1/3Nb2/3)x]O3, where x = 0.1, 0.3 and 0.5 were prepared using the columbite–(wolframite) precursor method. The general trend seems to indicate that the annealed samples become more normal-ferroelectric-like behavior as opposed to the relaxor-ferroelectric-like behavior observed in the as-sintered state. The as-sintered 0.9PZT–0.1PZN ceramic exhibited weak relaxor-ferroelectric behavior, with a relatively low dielectric constant maximum of 14,000 measured at 1 kHz. Annealing resulted in a transition to normal-ferroelectric-like behavior, a shift in the dielectric maximum temperature from 360 °C to 350 °C, and a dramatic increase in the dielectric constant at 1 kHz to a maximum value of 35,000 for the longer anneal. After thermal annealing at 900 °C for one week a strong enhancement of remanent polarization (Pr) was observed.

Piezoelectric Multilayer Ceramic/Polymer Composite Transducer with 2–2 Connectivity

A multilayer piezoelectric ceramic/polymer composite with 2–2 connectivity was fabricated by thermoplastic green machining after co‐extrusion. The multilayer ceramic body was composed of piezoelectrically active lead zirconate titanate (PZN)–lead zinc niobate (PZN)‐lead zirconate titanate (PZT) layers and electrically conducting PZN–PZT/Ag layers. After co‐extruding the thermoplastic body, which consisted of five piezoelectric layers interspersed with four conducting layers, it was computer numeric‐controlled machined to create periodic channels within it. Following binder burnout and sintering, an 18 vol% array of 190 μm thin PZT slabs with a channel size of 880 μm was fabricated. The channels were filled with epoxy in order to fabricate a PZN–PZT/epoxy composite with 2–2 connectivity. The piezoelectric coefficient (effective d33) and hydrostatic figure of merit (dh×gh) of the PZN–PZT/epoxy composite were 1200 pC/N and 20 130 × 10−15 m2/N, respectively. These excellent piezoelectric characteristics as well as the relatively simple fabrication procedure will contribute in widening the application range of the piezoelectric transducers.

Effects of excess ZnO addition on La-doped PZN–PZT ceramics prepared by hot pressing

Effects of excess ZnO addition on phase structure, dielectric and piezoelectric properties in La-doped Lead zinc niobate, Pb(Zn 1/3Nb 2/3)O 3 (PZN)–PZT systems have been investigated. Addition of excess ZnO helps to suppress the formation of the pyrochlore phase. Microstructure revealed the grains size to decrease with excess ZnO addition. Enhanced T max and d 33, and reduced ɛ max and Tan δ were observed. Adding proper excess ZnO in La-like doped PZN-based systems seems an effective approach to suppress the formation of the pyrochlore phase, enhance piezoelectric constant d 33 and reduce dielectric loss.

Pressure instabilities up to46GPain the relaxor ferroelectricPbZn1∕3Nb2∕3O3

We report a high-pressure investigation of the relaxor ferroelectric lead zinc niobate PbZn1/3Nb2/3O3 (PZN) up to 46 GPa, which is the highest pressure yet attained in the study of relaxors. The evolution of both Raman and x-ray scattering with pressure gives evidence for important pressure instabilities, which find its expression in three successive phase transitions. The observed pressure-induced suppression of diffuse scattering above 5 GPa is similar to recent reports and supports the hypothesis that this is a general feature in relaxors at high pressures.

Transitions in Morphotropic PMN-PT Single Crystals

Single crystals in the relaxor-ferroelectric lead magnesium niobate (PMN)-lead titanate (PT) and lead zinc niobate (PZN)-lead titanate (PT) systems provide a significant advantage for detecting and classifying objects in littoral waters. Their extremely large electromechanical coupling factor (k 33 > 0.90) and piezoelectric coefficient (d 33 > 1000 pC/N) offer both broadband and high acoustic source level capabilities. Two different transition pathways can be accessed in a morphotropic PMN-0.30PT composition. Resonance experiments on a length extensional bar fabricated from a multi-domain, [001] oriented and poled PMN- 0.30PT crystal revealed a monotonically decreasing Young's modulus as a function of temperature with a sudden stiffening near 85°C corresponding to a ferroelectric rhombohedral (F R )-ferroelectric tetragonal (F T ) transition. Quasi-static, zero field stress-strain response revealed an elastic instability of the F R near 30 MPa compression. This instability is attributed to a ferroelectric rhombohedral (F R )–ferroelectric orthorhombic (F O ) transition. A dc bias field of 0.59 MV/m stabilized the F R state up to 40 MPa compressive stresses. The implications of these results on sonar projector design and performance will be discussed.

Normal-to-relaxor ferroelectric transformations in lanthanum-modified lead zinc niobate–lead zirconate titanate (PZN–PZT) ceramics

Dielectric permittivities of unpoled and poled lanthanum-modified lead zinc niobate–lead zirconate titanate (PZN–PZT) ceramics were investigated. Results showed that the relaxor characteristics were enhanced with an increase in La doping. Two characteristic temperatures Tnr (normal-to-relaxor transformation) and Trt (rhombohedral-to-tetragonal phase transition) were spontaneously observed in the poled specimens. Tnr and Trt both decreased with increasing La doping content. Temperature-dependent Sawyer–Tower polarization studies revealed a double hysteresis loop near Trt. The presence of the double hysteresis loop and the step in permittivity–temperature curves at Trt might imply a rhombohedral-to-tetragonal phase transition.

Superior electromechanical performance over PZT, in lead zinc niobate (PZN)–lead zirconium titanate (PZT) thin films

Strongly oriented thin films of lead zinc niobate (PZN)–lead zirconium titanate (PZT) with (La,Sr)CoO3 lower electrodes were grown on MgO {001} substrates by pulsed laser deposition. The films were perovskite-dominated with strong in-plane and out-of-plane orientations. Room-temperature functional characterisation indicated that the films were ferroelectric, with dielectric constant ∼550 and loss tangent ∼0.08 at 1 kHz. The crystallographic strain, as a function of applied dc field, was monitored by in situ X-ray diffraction. The maximum electric-field-induced crystallographic strain (∼0.22%) was comparable to that observed in bulk, but at significantly greater field (∼150 kV cm-1). The effective d33 value obtained from the crystallographic strain data was around 150 pm V-1, which is high for ferroelectric thin films 400 nm in thickness. The local polarisation-switching properties of the films were investigated using a piezo-response atomic force microscope. Domain maps for a 5×5 μm2 region of material were recorded as a function of dc bias, and confirmed the ferroelectric switching behaviour.

Dielectric and ferroelectric characteristics of 0.7PZT–0.3PZN ceramics substituted with Sr

Lead zirconate titanate–lead zinc niobate (PZT–PZN) ceramics with compositions close to the morphotropic phase boundary were investigated as a function of Sr doping. The powders were prepared using the columbite-(wolframite) precursor method. Dielectric and ferroelectric properties of the as-sintered and annealed samples were measured. The results showed that with increasing Sr concentration dielectric constant versus temperature curves become gradually broader. Sr doping has been shown to produce a linear reduction in the transition temperature (Tm) (294.1−12.7x °C) with concentration (x). The maximum value of the dielectric constant decreased and the degree of diffuse phase transition was enhanced with Sr doping. However, the results indicated that the degree of disorder in Sr-modified PZT–PZN was further improved by thermal annealing. After thermal annealing at 900°C for 48 h a strong enhancement of dielectric constant (εr) and remanent polarization (Pr) was observed.

Sol–Gel Preparation of Thick PZN–PZT Film Using a Diol‐Based Solution Containing Polyvinylpyrrolidone for Piezoelectric Applications

Dense and crack‐free lead zinc niobate–lead zirconate titanate (PZN–PZT) films were deposited on silicon and glass substrates by spin coating using a sol containing propanediol and polyvinylpyrrolidone. Single‐layer PZN–PZT films as thick as 0.80 μm were deposited by a single spin coating with successive heat treatments at 250° and 700°C. After heat treatment, the films were dense, crack free, and optically transparent. In addition, the crystallographic orientation of the thick film was controllable by adjusting the heat‐treatment conditions. The ferroelectric properties of the (111)‐oriented film were superior to those of the (100)‐oriented film. On the other hand, the piezoelectric and dielectric properties of the (100)‐oriented film were better than those of the (111)‐oriented film. The piezoelectric coefficients (d33) of the PZN–PZT films of 4.0‐μm‐thickness were 192 and 110 pC/N for the (100)‐and (111)‐oriented films, respectively.

Water-Induced Degradation in Lead Zinc Niobate–Lead ZirconateTitanate Soft Piezoelectric Ceramics

Water-induced degradation of lead zinc niobate–lead zirconate titanate(Pb(Zn1/3Nb2/3)O3–Pb(ZrTi)O3) softpiezoelectric ceramics is studied using electrochemical hydrogencharging, in which the silver electrodes of the piezoelectric ceramicsconstitute a cathode in 0.01-M NaOH solution to evolve hydrogen byelectrolysis of water. It is found that with the increasing hydrogencharging time, the resonance impedance increases, the differencebetween the resonance frequency and the anti-resonance frequencydecreases, the spontaneous polarization, the remanent polarization andthe piezoelectric coefficient d33 decrease. Thedegradation behaviour of the soft piezoelectric ceramics can beexplained to hydrogen incorporating into the lattice and forminghydroxy (OH−) bonds in the perovskite structure, which preventsthe Ti ions from switching and increases the coercive field Ec. Thedegradation characteristics of the soft piezoelectric ceramics are quitedifferent from that of lead zirconate titanate hard piezoelectric ceramics.

The influence of fabrication processing on domain structure and polarization switching in PZN-based ferroelectric ceramics

Lead zinc niobate (Pb(Zn 1/3Nb 2/3)O 3, PZN) based ceramics are prepared by using conventional mixing oxide and complex phase reaction-sintering ceramic techniques. From the results of X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), it is clear that these two fabrication processing routes produce different microstructures and ferroelectric domains in the same Pb(Zn 1/3Nb 2/3)O 3–BaTiO 3–Pb(Zr 0.4Ti 0.6)O 3 composition. Furthermore, different phase transitions are observed for the temperature dependence of the dielectric permittivity that can be confirmed by differential scanning calorimetry (DSC). Different polarization switching characteristics are also examined by using high field-induced strain and ferroelectric hysteresis loop. It is suggested that the distribution of the inner stress and domain configuration should be related with the fabrication processing of ferroelectric ceramics.

Reaction sintering of lead zinc niobate–lead zirconate titanate ceramics

Lead zinc niobate (PZN)–lead zirconate titanate (PZT) ceramics were produced by the reaction-sintering process. The specimens were prepared directly from a mixture of their constituent oxides without any calcination step. When 50% PZN was added to tetragonal Pb(Zr 0.47Ti 0.53)O 3 ceramics, the densities and electrical properties were found to be optimal ( ρ = 7.91 g/cm 3, K = 1947 at 1 kHz and room temperature, d 33 = 530 pC/N, k p = 0.61). However, the specimen containing more than 50% PZN showed reduced density and decreased electrical properties, due to the formation of pyrochlore phases. The improved densification behavior of the reaction-sintering process was attributed to the enhanced diffusion of lattice defects, which were created by differences in the ionic valence of the B-sites ions of the perovskite structure.

Piezocrystal-polymer composites: new materials for transducers for ultrasonic NDT

Piezoceramic-polymer composite materials are finding increasing acceptance in ultrasonic transducers for NDT. However, new piezocrystal materials are also becoming available, such as lead zinc niobate doped with lead titanate (PZN-PT). Made into piezocomposite, they have significant theoretical performance advantages. Although the new materials are presently more expensive than piezoceramic, their prices have recently fallen dramatically, making them viable for high-end NDT. In this paper, the authors first review the background to the new piezocrystals then report their experience in piezocomposites made with them. The authors describe how they have predicted the main piezoelectric properties of these piezocomposites, establishing a robust design process. The composite fabrication method is outfitted and the properties for four different single-crystal volume fractions are reported. Prototype elements have been realised in the form of coupons approximately 5 mm x 10 mm suitable for dual-element probes and these probes have been evaluated on test objects of various materials, including a steel block, an aluminium block and a carbon fibre reinforced composite (CFRC) panel. The results confirm that the theoretical performance advantages can be achieved in practice, including doubling the gain-bandwidth product compared with conventional piezoceramic-polymer composite. It is concluded that applications such as ultrasonic spectroscopy, inspection of difficult materials and multi-element imaging arrays may benefit significantly.