Showing papers on "Lead zirconate titanate published in 1999"
TL;DR: Ferroelectric ceramics have been the heart and soul of several multibillion dollar industries, ranging from high-dielectric-constant capacitors to later developments in piezoelectric transducers, positive temperature coefficient devices, and electrooptic light valves as mentioned in this paper.
Abstract: Ferroelectric ceramics were born in the early 1940s with the discovery of the phenomenon of ferroelectricity as the source of the unusually high dielectric constant in ceramic barium titanate capacitors. Since that time, they have been the heart and soul of several multibillion dollar industries, ranging from high-dielectric-constant capacitors to later developments in piezoelectric transducers, positive temperature coefficient devices, and electrooptic light valves. Materials based on two compositional systems, barium titanate and lead zirconate titanate, have dominated the field throughout their history. The more recent developments in the field of ferroelectric ceramics, such as medical ultrasonic composites, high-displacement piezoelectric actuators (Moonies, RAINBOWS), photostrictors, and thin and thick films for piezoelectric and integrated-circuit applications have served to keep the industry young amidst its growing maturity. Various ceramic formulations, their form (bulk, films), fabrication, function (properties), and future are described in relation to their ferroelectric nature and specific areas of application.
3,442 citations
TL;DR: In this paper, the authors show that lanthanum-substituted bismuth titanate (SBT) thin films provide a promising alternative for FRAM applications, since they are fatigue-free on metal electrodes, they can be deposited at temperatures of ∼650°C and their values of Pr are larger than those of the SBT films.
Abstract: Non-volatile memory devices are so named because they retain information when power is interrupted; thus they are important computer components. In this context, there has been considerable recent interest1,2 in developing non-volatile memories that use ferroelectric thin films—‘ferroelectric random access memories’, or FRAMs—in which information is stored in the polarization state of the ferroelectric material. To realize a practical FRAM, the thin films should satisfy the following criteria: compatibility with existing dynamic random access memory technologies, large remnant polarization (Pr) and reliable polarization-cycling characteristics. Early work focused on lead zirconate titanate (PZT) but, when films of this material were grown on metal electrodes, they generally suffered from a reduction of Pr (‘fatigue’) with polarity switching. Strontium bismuth tantalate (SBT) and related oxides have been proposed to overcome the fatigue problem3, but such materials have other shortcomings, such as a high deposition temperature. Here we show that lanthanum-substituted bismuth titanate thin films provide a promising alternative for FRAM applications. The films are fatigue-free on metal electrodes, they can be deposited at temperatures of ∼650 °C and their values of Pr are larger than those of the SBT films.
2,008 citations
TL;DR: In this article, the Schottky barrier heights of various metals on the high permitivity oxides tantalum pentoxide, barium strontium titanate, lead zirconate titanate (LZT), and strontia bismuth tantalate have been calculated as a function of the metal work function.
Abstract: The Schottky barrier heights of various metals on the high permitivity oxides tantalum pentoxide, barium strontium titanate, lead zirconate titanate, and strontium bismuth tantalate have been calculated as a function of the metal work function. It is found that these oxides have a dimensionless Schottky barrier pinning factor S of 0.28–0.4 and not close to 1 because S is controlled by Ti–O-type bonds not Sr–O-type bonds, as assumed in earlier work. The band offsets on silicon are asymmetric with a much smaller offset at the conduction band, so that Ta2O5 and barium strontium titanate are relatively poor barriers to electrons on Si.
364 citations
TL;DR: In this paper, the microstructure and chemical composition of lead zirconate titanate (PZT) films were investigated by transmission electron microscopy (TEM) and energy dispersive X-ray spectra (EDX) analysis.
Abstract: Lead zirconate titanate (PZT) films with a thickness of more than 10 µm were prepared by the aerosol deposition method and their microstructure and chemical composition were investigated by transmission electron microscopy (TEM) and energy dispersive X-ray spectra (EDX) analysis. A damage layer was observed at the interface between PZT and the Si substrate during the deposition. The microstructure of the as-deposited film at room temperature consisted of randomly oriented small crystallites with sizes of less than 40 nm and large crystallites of 100 nm to 300 nm size, which were observed in the primary powder. The Pb/Ti/Zr ratio along the film stacking direction and around the grain boundaries was almost the same as that observed inside the crystallites and the primary powder with a morphotropic phase boundary composition of (Pb(Zr0.52Ti0.48)O3). The marked improvement of the electrical properties observed in the deposited films after annealing was mainly due to the crystal growth of small crystallites.
266 citations
TL;DR: The polarization field of the ferroelectric oxide lead zirconate titanate was used to tune the critical temperature of the hightemperature superconducting cuprate gadolinium barium copper oxide in a reversible, nonvolatile fashion.
Abstract: The polarization field of the ferroelectric oxide lead zirconate titanate [Pb(ZrxTi1–x)O3] was used to tune the critical temperature of the hightemperature superconducting cuprate gadolinium barium copper oxide (GdBa2Cu3O7–x) in a reversible, nonvolatile fashion. For slightly underdoped samples, a uniform shift of several Kelvin in the critical temperature was observed, whereas for more underdoped samples, an insulating state was induced. This transition from superconducting to insulating behavior does not involve chemical or crystalline modification of the material.
246 citations
TL;DR: In this paper, the nonlinear electromechanical behavior of cantilevered piezoelectric ceramic bimorph, unimorph, and reduced and internally biased oxide wafer actuators is studied in a wide electric field and frequency range.
Abstract: The nonlinear electromechanical behavior of cantilevered piezoelectric ceramic bimorph, unimorph, and reduced and internally biased oxide wafer actuators is studied in a wide electric field and frequency range. It is found that under quasistatic condition, linear relationships between actuator tip displacement-electric field, and blocking force-electric field are only valid under weak field driving. With increasing the driving field, electromechanical nonlinearity begins to contribute significantly to the actuator performance because of ferroelectric hysteresis behavior associated with piezoelectric lead zirconate titanate (PZT)-type ceramic materials. The bending resonance frequencies of all these actuators vary with the magnitude of the electric field. The decrease of resonance frequency with electric field is explained by the increase of elastic compliance of PZT ceramic due to elastic nonlinearity. Mechanical quality factors of the actuators also depend on the magnitude of electric field strength. No significant temperature increase is observed when actuators are driven near resonance frequency under high electric field.
225 citations
TL;DR: In this paper, the transition lines between various phases in the electric-field-temperature phase diagram of 9/65/35 lanthanum-modified lead zirconate titanate ceramics were determined by measurements of the temperature and electric field-dependent dielectric constant.
Abstract: Transition lines between various phases in the electric-field--temperature phase diagram of 9/65/35 lanthanum-modified lead zirconate titanate ceramics were determined by measurements of the temperature and electric-field-dependent dielectric constant. Above a critical field ${(E}_{C})$ the dc bias electric field induces a transition from the relaxor (R) to the long-range ferroelectric (FE) phase. In the temperature direction of the approach to the FE phase the R-FE transition line was determined from the field-cooled--field-heated dielectric susceptibilities, while depolarization temperatures were obtained from the field-cooled--zero-field-heated dielectric susceptibilities. A considerably large shift was found for the above two R-FE transition lines demonstrating the strong impact of the electric field on the stability of the FE phase with increasing temperature. It was found that below ${E}_{C}$ ergodicity is broken due to the divergence of the longest relaxation time at the freezing temperature ${T}_{0}=259 \mathrm{K}.$ Hence the system exhibits a transition line between the ergodic (ER) and nonergodic (NR) relaxor state. In the dc bias field direction of the approach to the FE phase, the temperature dependence of ${E}_{C},$ i.e., the transition lines between ER or NR and FE phases were studied by measurements of the complex dielectric constant as a function of a dc bias field at several fixed temperatures. The experimental results are compared with the results of a spherical random bond-random field model of relaxor ferroelectrics.
176 citations
TL;DR: Although soft PZT ceramics can be easily stress depoled (losing piezoelectricity), a DC bias electric field can be employed to maintain the ceramic poling state so that the ceramic can be used at high stresses without depoling.
Abstract: In lead zirconate titanate piezoceramics, external stresses can cause substantial changes in the piezoelectric coefficients, dielectric constant, and elastic compliance due to nonlinear effects and stress depoling effects. In both soft and hard PZT piezoceramics, the aging can produce a memory effect that will facilitate the recovery of the poled state in the ceramics from momentary electric or stress depoling. In hard PZT ceramics, the local defect fields built up during the aging process can stabilize the ceramic against external stress depoling that results in a marked increase in the piezoelectric coefficient and electromechanical coupling factor in the ceramic under the stress. Although soft PZT ceramics can be easily stress depoled (losing piezoelectricity), a DC bias electric field, parallel to the original poling direction, can be employed to maintain the ceramic poling state so that the ceramic can be used at high stresses without depoling.
171 citations
TL;DR: In this paper, high-density lead zirconate titanate (PZT) ceramics were successfully prepared by using a novel mechanochemical fabrication technique, which skips the phase-forming calcination at an intermediate temperature that is always required in the industrial processes currently in use.
Abstract: High-density lead zirconate titanate (PZT) ceramics have been successfully prepared by using a novel mechanochemical fabrication technique, which skips the phase-forming calcination at an intermediate temperature that is always required in the industrial processes currently in use. The fabrication technique starts with mixing of the low-cost industrial oxide powders, and the designed PZT perovskite phase is formed by reacting the oxide constituents in a mechanochemical chamber that consists of a cylindrical alumina vial and one stainless-steel ball inside it. The solid-state reaction among constituent oxides is activated via mechanical energy instead of high temperature. When mechanochemically activated for 20 h, an ultrafine PZT powder of perovskite structure with a minimized degree of particle agglomeration is obtained. The resulting PZT powder sinters to 99.0% of theoretical density at 1100°C for 1 h. The sintered PZT ceramic exhibits a dielectric constant of 1340 and a dielectric loss of 0.6% at a frequency of 1 kHz at room temperature.
155 citations
TL;DR: In this article, the freezing of the dynamic process in a 9/65/35 lanthanum lead zirconate-titanate (PLZT) ceramics has been investigated by measurements of the frequency-dependent complex dielectric constant and the quasistatic field-cooled (FC) and zero-field cooled (ZFC) susceptibilities.
Abstract: The freezing of the dynamic process in a 9/65/35 lanthanum lead zirconate-titanate (PLZT) ceramics has been investigated by measurements of the frequency-dependent complex dielectric constant and the quasistatic field-cooled (FC) and zero-field-cooled (ZFC) dielectric susceptibilities. It was found that the aging process is responsible for the difference in temperature variations of the FC static dielectric constant and the static dielectric constant determined in the dynamic ZFC experiment. Analysis of the complex dielectric susceptibility by a temperature-frequency plot has revealed that for an aged PLZT sample the ergodicity is broken due to the divergence of the longest relaxation time in the vicinity of 249 K, i.e., the temperature where the ferroelectric phase can also be induced by applying sufficiently high electric field. However, the bulk of the distribution of relaxation times was found to remain finite even below the freezing temperature. It is shown that the behavior of the relaxation spectrum and the splitting between the field-cooled and zero-field-cooled dielectric constants in PLZT relaxor is qualitatively similar to what was observed in the lead magnesium niobate (PMN) relaxor and is reminiscent of the nonergodic behavior reported in various spin glasses. Moreover, the temperature dependence of the third order nonlinear susceptibility indicates a glassy rather than ferroelectric multidomain nature of the nonergodic relaxor state in both PMN and PLZT systems.
151 citations
TL;DR: In this article, band structure match-ups for the electrode interfaces between platinum electrodes and the ferroelectric thin-film materials commonly used for DRAMs and nonvolatile FRAMs were given theoretically from X-ray photoemission spectroscopy (XPS).
Abstract: Band structure match-ups are given theoretically from X-ray photoemission spectroscopy (XPS) for the electrode interfaces between platinum electrodes and the ferroelectric thin-film materials commonly used for random access memories (DRAMs and nonvolatile FRAMs): strontium bismuth tantalate (SBT), barium strontium titanate (BST), and lead zirconate titanate (PZT). The results all agree with experimentally measured Schottky barrier heights. The electronegativity constant or S-factor (derivative of Schottky barrier height with respect to electron affinity) is found to be approximately 0.7 for these materials, not the purely ionic value of 1.0. The reduction of a factor of a million in the effective Richardson coefficient is explained. And the paradox of avalanche breakdown but decreasing breakdown fields with increasing temperature is reconciled.
TL;DR: In this paper, a metastable Pt3Pb intermetallic phase has been identified, and the formation of this metastable phase was found to depend on the drying temperature, the thickness of the as-deposited film, annealing temperature, and anneal time.
Abstract: Pyroelectric lead zirconate titanate (PZT) thin films have been prepared by a sol-gel method and characterized by x-ray diffraction and transmission electron microscopy (TEM). A metastable Pt3Pb intermetallic phase has been identified. The formation of this metastable phase was found to depend on the drying temperature, the thickness of the as-deposited film, annealing temperature, and annealing time. Perovskite PZT was found to nucleate on top of the intermetallic phase, rather than directly on Pt. The improved lattice match between the intermetallic (a0=4.05 A) and perovskite PZT(a0=4.035 A) as compared to between Pt(a0=3.9231 A) and the perovskite is believed to substantially reduce the activation energy for the nucleation of perovskite on Pt. Using this effect, (111) perovskite PZT has been grown at a temperature as low as 440 °C. The formation of the intermetallic phase is believed to facilitate the (111) film orientation. The growth kinetics of the PZT were analyzed using the Avrami model, and from ...
TL;DR: In this article, the effect of misfit strain on the microstructure and properties of ferroelectric lead zirconate titanate thin films was studied by varying the film thickness and the thickness effect on domain formation of epitaxial PbZr02Ti08O3 (PZT) films.
Abstract: We have studied the effect of misfit strain on the microstructure and properties of ferroelectric lead zirconate titanate thin films We have changed the misfit strain by varying the film thickness and studied the thickness effect on the domain formation of epitaxial PbZr02Ti08O3 (PZT) films grown by pulsed laser deposition on (001) LaAlO3 substrates with La05Sr05CoO3 (LSCO) electrodes The nominal thickness of the PZT films was varied from 60 to 400 nm with the LSCO electrode thickness kept constant at 50 nm X-ray diffraction experiments show that the films relax via the formation of a domains, the fraction of which increase with the ferroelectric film thickness The c-axis lattice constant of PZT films calculated from the 002 reflection decreases with increasing film thickness and approaches the bulk value of ∼0413 nm in the films thicker than 300 nm Cross-sectional transmission electron microscopy images reveal that the a-domain fraction and period increase with increasing film thickness The relaxation of misfit strain in the film is accompanied by systematic changes in the polarization properties, as well as the switching fields, quantified by the coercive field and the activation field
TL;DR: In this paper, the d31 coefficient of a number of sputtered lead zirconate titanate (PZT) thin films with thicknesses between 0.6 and 3 μm was analyzed.
Abstract: The wafer flexure technique was used to characterize the d31 coefficient of a number of sol–gel and radio frequency (rf) sputtered lead zirconate titanate (PZT) thin films with thicknesses between 0.6 and 3 μm. Typical d31 values for well-poled 52/48 sol–gel films were found to be between −50 and −60 pC/N. The rf sputtered films possessed large as-deposited polarizations which produced d31 coefficients on the order of −70 pC/N in some unpoled films. The subsequent poling of the material, in a direction parallel to the preferred direction increased the d31 coefficient to values of about −85 pC/N. The aging behavior of the d31 coefficient was also investigated. For sol–gel films the aging rate was found to be independent of poling direction and to range from 4% per decade for a 2.5 μm film to 8% per decade for a 0.6 μm film. In contrast, the aging rate of sputtered films was strongly dependent on poling direction, with maximum and minimum rates of 26% and 2% per decade recorded. These aging rates are very h...
TL;DR: In this article, a pneumatic pressure rig was designed to measure the effective d33 coefficient of thin film piezoelectrics by applying a known stress and monitoring the induced charge.
Abstract: A pneumatic pressure rig was designed to measure the effective d33 coefficient of thin film piezoelectrics by applying a known stress and monitoring the induced charge. It was found that the stress state imposed included components both perpendicular and parallel to the film plane. The later were due to friction and could largely be relieved through sliding of the O-rings to their equilibrium positions for a given pressure. The induced charge stabilized as equilibrium was reached and most of it was produced by the normal component of the stress. By minimizing the surface friction and compensating for the remnant in-plane stress, very good agreement was obtained among the d33 values measured by the Berlincourt method, double-beam interferometry and this method for a bulk lead zirconate titanate (PZT) sample. The d33 value of PZT thin films made by sol-gel processing was also measured. The as deposited films usually showed very weak piezoelectricity with d33 values ranging from 0 to 10 pC/N, indicating little pre-existing alignment of the domains. With increasing poling field, the d33 value also increased and saturated at poling fields exceeding three times the coercive field. Typically, films with thicknesses around 1 μm had d33 values of 100 pC/N. Good agreement between double-beam interferometry and this technique was also obtained for thin films. The small difference between the two measurements is attributed to the effect of mechanical boundary conditions on the effective d33 coefficient.
TL;DR: In this paper, the Avrami coefficient n and growth rate constant k were determined by comparing the experimental results and the simulated curves, from which activation energies of 40 and 145 kJ/mol were obtained for the growth and decay of the intermetallic Pt3Pb phase, respectively.
Abstract: Lead zirconate titanate (PZT) thin films on platinized silicon were fabricated and their structural development upon annealing was characterized by x-ray diffraction and transmission electron microscopy (TEM). The amount of a transient intermetallic phase Pt3Pb was found initially to increase with annealing time and to decay after reaching a maximum. The kinetic process of growth and decay was simulated by using the Avrami equation. The Avrami coefficient n and growth rate constant k were determined by comparing the experimental results and the simulated curves, from which activation energies of 40 and 145 kJ/mol were obtained for the growth and decay of the intermetallic Pt3Pb phase, respectively. The perovskite PZT was found by using TEM to nucleate epitaxially on top of the Pt3Pb phase. Evidence is presented that the Pt3Pb phase plays a major role in determining the crystallite’s orientation at the nucleation stage of the perovskite PZT. This depends strongly on the annealing temperature and the orient...
TL;DR: In this article, the effect of standard photolithography and micromachining upon the printed lead zirconate titanate (PZT) layer has been investigated, in particular the adhesion of the printed layer to the substrate and its internal structure after exposure to each process.
Abstract: Thick-film printed lead zirconate titanate (PZT) structures can be combined with micromachined silicon structures and offer relatively large actuation forces compared to alternative techniques. This paper describes the initial investigation into the compatibility issues of micromachining silicon wafers with PZT layers printed on the surface. It assesses the effect of many standard photolithography and micromachining upon the printed PZT layer. In particular the adhesion of the printed layer to the substrate and its internal structure have been studied after exposure to each process. Standard photolithography using positive resists has been found to destroy the adhesion of the platinum electrode and an alternative masking technique using a thick-film printed dielectric polymer has been developed. Aluminium top electrodes have been fabricated using this masking technique combined with ion beam milling. Finally many standard micromachining etching processes have been carried out on a range of silicon substrates incorporating platinum electrode/thick-film PZT structures. Wet silicon and silicon dioxide etches were found to be unsuitable since they also attacked the adhesion of the bottom electrode. Plasma etching processes appear to be well suited for the combination of materials since there is a wide range of etches available that do not affect the PZT. These can therefore be used for the micromachining of the silicon substrate after thick-film processing greatly expanding the range of applications suited to this combination of technologies.
TL;DR: In this article, the dependence of polarization switching on thermal histories has been investigated for K1+-modified lead zirconate titanate (PZT) ceramics by Sawyer-Tower polarization methods.
Abstract: The dependence of polarization switching on thermal histories has been investigated for K1+-modified lead zirconate titanate (PZT) ceramics by Sawyer–Tower polarization methods. It was found that double-loop-like polarization characteristics in the aged condition could be reversed to normal single loop polarization characteristics by quenching specimens from above the ferroelectric phase transition temperature. However, the P–E curves reversed back to double-loop-like characteristics after reaging specimens at elevated temperatures. Excess oxygen vacancies in La3+-modified PZT were not found to result in double-loop-like polarization hysteresis, whereas excess oxygen vacancies in K1+-modified PZT did. These results provide evidence for role of K1+-oxygen vacancy complexes in polarization pinning.
TL;DR: In this paper, a 10-μm PZT film was formed from the same starting powder and exhibited a polarization hysteresis equivalent to that of a bulk sample, with a remnant polarization of 33μC−cm−2.
Abstract: Electrophoretic deposition (EPD) is a simple, rapid, and low cost method for forming dense lead zirconate titanate (PZT) films down to 5 μm from particulate precursors. The three main steps of this process are: (1) formation of a charged suspension of the starting PZT powder; (2) deposition of the powder particles on an electrode under the influence of a dc electric field; and (3) fluxing and constrained sintering of the resulting particulate deposit at 900°C to form a dense continuous film. A 10 μm film formed using this process exhibited a polarization hysteresis equivalent to that of a bulk sample formed from the same starting powder, with a remnant polarization of 33 μC cm−2.
TL;DR: In this article, the authors studied the piezoelectric properties of lead-free bismuth layer structure oxide, SrBi4Ti4O15 (SBT) based ceramics, and found that the maximum value of Q (Qmax ) between resonant frequency and anti-resonant frequency was larger than that of SBT.
Abstract: Piezoelectric properties of lead-free bismuth layer structure oxide, SrBi4Ti4O15 (SBT) based ceramics, were studied. By means of La substitution and Mn addition, the maximum value of Q (Qmax ) between resonant frequency and anti-resonant frequency was larger than that of SBT. These materials could be utilized in practical applications as substitutes for lead titanate based ceramics (PT) and lead zirconate titanate based ceramics (PZT) which are used mainly in resonators. The reason for the higher Qmax value was identified by microstructual analysis as being due to the absence of a defect structure.
TL;DR: In this article, lead zirconate titanate (PZT) thin films with transverse electric fields driven by interdigitated surface electrodes were used for high-resolution acoustic imaging.
Abstract: Excellent symmetric dielectric hysteresis is observed from lead zirconate titanate (PZT) thin films using transverse electric fields driven by interdigitated surface electrodes. The 1-μm-thick PZT films with a Zr/Ti ratio of 52/48 are prepared on ZrO2 buffered, 4-in.-diam silicon wafers with a thermally grown SiO2 layer. Both the ZrO2 buffer layer and PZT film are deposited by using a similar sol–gel processing. Remanent polarization of about 20 μC/cm2 with coercive field less than 40 kV/cm is obtained as measured using a triangle wave at 50 Hz. Thicker films are being developed and retention for the transversely polarized state is currently under study. One of the objectives of this study is to develop a large array of d33-driven unimorph sensing elements for a high-resolution acoustic imaging system.
TL;DR: In this article, a micro ultrasonic motor composed of bulk lead zirconate titanate (PZT) thin film transducers was used for a two-axis hand application.
Abstract: Ultrasonic motors are expected to be used as microactuators because of their high torque, low speed and simple construction. We have already reported cylindrical-shaped micro ultrasonic motors which utilized a lead zirconate titanate (PZT) thin film. In this paper, we discuss a micro ultrasonic motor composed of bulk PZT. The stator transducer had dimensions of 2.4 mm in diameter and 10 mm length. The maximum revolution speed was 650 rpm and the maximum output torque was 0.22 mNm with the condition of 100 Vp-p input voltage. The driving frequency was 85 kHz. The comparison between the bulk PZT stator transducer and the previous PZT thin film transducer was considered. From this consideration, thee31 piezoelectric factor was determined to be the main factor for different output torques. The bulk PZT motor was applied to robot hands which was a simple procedure. A two axes hands application was successfully operated with a step motion and carried up to a 10 g load.
TL;DR: In this paper, the PZT powder was incorporated into a P(VDF-TrFE) copolymer matrix for pyroelectric sensor and piezoelectric transducer applications.
Abstract: Lead zirconate titanate/vinylidene fluoride-trifluoroethylene [PZT/P(VDF-TrFE)] 0–3 composites for pyroelectric sensor and piezoelectric transducer applications have been fabricated by incorporating PZT powder into a P(VDF-TrFE) copolymer matrix. The properties of these composites can be tailored to suit designated applications by varying the ceramic volume fraction and by using different poling procedures. As both phases in the composite are ferroelectric, and the piezoelectric coefficients of the ceramic and copolymer phases have opposite signs while the pyroelectric coefficients have like signs, special ways can be used to produce three groups of samples with (1) only the ceramic phase poled, (2) two phases poled in the same direction to achieve reinforced pyroelectric activity and reduced piezoelectric activity, and (3) two phases poled in opposite directions to obtain reinforced piezoelectric activity and reduced pyroelectric activity. In this work, original experimental results on the properties of ...
TL;DR: In this article, a wide range of ceramics have been demonstrated, including aluminium oxide, silica, hydroxyapatite, silicon nitride, and lead zirconate titanate, with techniques based on extrusion, ink jet deposition, green tape lamination, and photopolymerisation.
Abstract: Fabrication of ceramic objects by solid freeform fabrication (SFF) techniques is reviewed, with emphasis on ceramic versions of commercial rapid prototyping (RP) methods. A wide range of ceramics have been demonstrated, including aluminium oxide, silica, hydroxyapatite, silicon nitride, and lead zirconate titanate, with techniques based on extrusion, ink jet deposition, green tape lamination, and photopolymerisation. The quality of SFF ceramics compares well with conventionally processed ceramics.
TL;DR: In this paper, the dependence of dielectric and ferroelectric properties on film thickness has been studied, with the emphasis on field-induced phase switching, and the decrease of film thickness also leads to a decrease of the phase switching fields, the appearance of remanent polarization in the hysteresis loops, and smearing of antiferroelectric-ferroelectric phase switching.
Abstract: Lanthanum-doped lead zirconate titanate stannate antiferroelectric thin films with compositions in antiferroelectric orthorhombic region have been prepared on Pt-buffered Si substrates by the sol–gel method, with the film thickness from 0.1 to 1.0 μm. The dependence of dielectric and ferroelectric properties on film thickness have been studied, with the emphasis on field-induced phase switching. The dielectric constant and maximum polarization decrease with the reduction of film thickness, which are similar to ferroelectric thin films. However, the decrease of film thickness also leads to the decrease of the phase switching fields, the appearance of remanent polarization in the hysteresis loops, and the smearing of antiferroelectric–ferroelectric phase switching. These phenomena are believed to be caused mainly by the stress effect between the film and substrate. Due to thermal mismatch, the films are under high tensile stress after annealing, and the stress effect becomes more significant with the decrea...
TL;DR: In this article, a small amount of silver was added to a lead zirconate titanate (PZT) matrix to accelerate the sinterability of the PZT composites.
Abstract: High-toughness and high-strength lead zirconate titanate (PZT) composites that contain fine silver particles were successfully fabricated at low sintering temperatures. Addition of silver to a PZT matrix did not result in unwanted reaction phases; however, some silver diffused toward the perovskite crystal structure. A small quantity of silver accelerated the sinterability of the PZT composites. The formation of oxygen vacancies due to the partial substitution of silver appeared to enhance the sinterability of the PZT. Fracture toughness depended on the size and degree of sphericity of the silver particles, and SEM observations on crack propagation suggested that the toughening mechanism in the PZT/Ag composites involves crack bridging resulting from the ductile behavior of silver particles. It is proposed that high fracture strength in PZT/1 to 5 vol% Ag composites results from the relaxation of transformation-induced internal stress by the silver particles.
TL;DR: In this paper, the response of lead zirconate titanate and barium titanate piezoelectric ceramics to spherical microindentation was investigated.
TL;DR: In this paper, a 96-channel phased array probe for echocardiography using a single-plate, 0.91Pb(Zn1/3Nb2/3)O3-0.09PbTiO3 (PZNT 91/9) single-crystal transducer with dimensions of 14×20 mm has been fabricated to realize greater sensitivity and broader bandwidth properties.
Abstract: A 96-channel phased array probe for echocardiography using a single-plate, 0.91Pb(Zn1/3Nb2/3)O3–0.09PbTiO3 (PZNT 91/9) single-crystal transducer with dimensions of 14×20 mm has been fabricated to realize greater sensitivity and broader bandwidth properties. The center frequency of the probe, 3.5 MHz, was selected to cover the bandwidths of two conventional lead zirconate titanate (PZT) ceramic probes with center frequencies of 2.5 and 3.75 MHz. A solder paste was used to connect a flexible printed circuit to the PZNT 91/9 transducer. The echo amplitude of the PZNT 91/9 probe is about 6 dB higher than that of the two PZT probes, and the fractional bandwidths are 30 and 25 percentage points wider, respectively. The B-mode image quality of the PZNT 91/9 probe is comparable to that of the two PZT probes, and the Doppler sensitivity of the PZNT 91/9 probe is almost equal to that of the 2.5 MHz PZT probe, which means that the PZNT 91/9 probe matches both the penetration of the 2.5 MHz PZT probe and the resolution of 3.75 MHz PZT probe.
TL;DR: In this paper, a two-dimensional lattice of dipoles is assumed to describe the thin film and the electric field distribution inside the film is calculated by solving Poisson's equation, which allows to locally determine the evolution of the polarization by minimizing free energy.
Abstract: During ion etching (IE) processes used for making a Pt electrode in the fabrication of ferroelectric capacitors, the film is exposed to radiation and energetic ion bombardment. The influence of such processes on polarization-electric field characteristics of lead zirconate titanate thin film capacitor has been reported by E. G. Lee [Appl. Phys. Lett. 69, 1223 (1996)]. A large field shift and a constriction in the hysteresis loop are experimentally observed. For these authors, this behavior is probably due to the existence of space charges trapped near electrodes. For a better understanding of these phenomena, we have developed a model of ferroelectric capacitor based on the phenomenological Landau–Devonshire theory. A two-dimensional lattice of dipoles is assumed to describe the film. By solving Poisson’s equation, the electric-field distribution inside the film is calculated, which allows us to locally determine the evolution of the polarization by minimizing free energy. IE effects and probably the existence of space charges in the film are introduced by means of a doping layer in the film near the electrode. The influence of important parameters such as doping level, and thickness of the doped layer on the hysteresis loop are investigated. Main experimental thin film electric behaviors are well reproduced and explained considering dipoles switched inside the lattice. Results are interpreted by splitting the hysteresis loop deformation into two effects with different origins: a constriction effect related to the number of impurities inside the film and a shift effect related to the asymmetrical impurities distribution.
15 Jan 1999-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: The mechanical properties of solution deposited lead zirconate titanate (PZT) thin films, including the hardness, modulus, and fracture behavior, have been studied using continuous indentation methods.
Abstract: The mechanical properties of solution deposited lead zirconate titanate (PZT) thin films; including the hardness, modulus, and fracture behavior, have been studied using continuous indentation methods. Comparisons are made between the behavior of the thin films and a bulk PZT ceramic. The thin films exhibit a hardness between 5 and 8 GPa, slightly lower than the hardness measured in a bulk PZT, ≈9 GPa. The increased grain boundary area in the thin films, which have 100 nm grain sizes, may act to accommodate plastic deformation. Fracture caused by indentations appears to be constrained to the sub-surface regions of the film, and no evidence of indentation induced delamination was observed. Traditional indentation analysis cannot accurately determine the elastic modulus of thin film PZT materials due to non-linear elastic behavior. The apparent modulus of the thin film PZT is insensitive to processing methods that alter the electrical properties of the film.