Showing papers on "Lead zirconate titanate published in 2000"

Piezoelectric properties of rhombohedral Pb(Zr, Ti)O3 thin films with (100), (111), and “random” crystallographic orientation

Abstract: The longitudinal d33 piezoelectric coefficient was studied in rhombohedral Pb(Zr0.6Ti0.4)O3 thin films with (111), (100), and “random” orientation. The largest d33 was found in (100)-oriented films and the smallest along the polarization direction in (111)-oriented films. These results are in a good qualitative agreement with recent theoretical predictions [Du, Zheng, Belegundu, and Uchino, Appl. Phys. Lett. 72, 2421 (1998)]. The field dependence of d33 was also investigated as a function of crystallographic orientation of the films. It was found that (100)-oriented films with the highest piezoelectric coefficient exhibit the weakest nonlinearity. Observed variation in the piezoelectric nonlinearity with film orientation can be fully explained by taking into account domain-wall contributions, which are dependent on film orientation.

Active micromixer for microfluidic systems using lead-zirconate-titanate (PZT)-generated ultrasonic vibration.

Abstract: A micromixer using direct ultrasonic vibration is first reported in this paper. The ultrasonic vibration was induced by a bulk lead-zirconate-titanate (PZT; 5 x 4 x 0.2 mm), which was excited by a 48 kHz square wave at 150 V (peak-to-peak). Liquids were mixed in a chamber (6 x 6 x 0.06 mm) with an oscillating diaphragm driven by the PZT. The oscillating diaphragm was in the size of 6 x 6 x 0.15 mm. Ethanol and water were used to test the mixing effectiveness. The laminar flows of ethanol (115 microL/min) and water (100 microL/min) were mixed effectively when the PZT was excited. The entire process was recorded using a video camera.

Role of 90° domains in lead zirconate titanate thin films

Abstract: We report observations of the ferroelectric domain structure in epitaxial lead zirconate titanate (PbZr0.2Ti0.8O3) ferroelectric thin films using piezoresponse microscopy. By manipulating the film thickness, a uniform two-dimensional grid of 90° domains (a domains, i.e., c axis in the plane of the film) has been induced. Our studies show that the out of plane polarization direction in the film is preferentially oriented. 90° domains have been observed as regions of low piezoresponse, as compared to the fully c axis oriented regions. We have studied the influence of these 90° domains and the domain walls on the nucleation of polarization reversal. We observe that the nucleation occurs preferentially at 90° domain interfaces. Polarization reversal is seen to occur through the nucleation and subsequent growth of “semicircular/elliptical” reverse domains, which eventually consume the entire region as a function of reversal time.

Effects of thickness on the piezoelectric and dielectric properties of lead zirconate titanate thin films

Abstract: Lead zirconate titanate (PZT) thin films with a Zr/Ti ratio of 52/48 were deposited on platinized silicon substrates by a sol-gel method and crystallized with preferred (111) or (100) orientation. Both the piezoelectric properties (d33) and the field-induced strains of the films with different thickness and preferred orientation were measured by a laser Doppler heterodyne interferometer. The weak-field dielectric constants and dissipation factors were also measured as a function of film thickness for comparison with other work reported in the literature. The field-forced polarization switching (P-E) behavior was examined by Sawyer–Tower measurement. Both the piezoelectric properties and the dielectric constants of the PZT thin films were found to be strongly dependent on the film thickness. An increase in the piezoelectric constants and dielectric constants with increasing film thickness was observed for both films with preferred (111) and (100) orientations. Films with (100) preferred orientation were fo...

Liquid-phase sintering of PZT ceramics

Abstract: Lead zirconate titanate (abbreviated as PZT) ceramics are of considerable commercial importance for a host of piezoelectric and pyroelectric applications. Conventionally, many PZT ceramics are sintered at temperatures above 1250°C. Such extreme temperatures are undesirable due to the increased energy consumption, limitation of electrode material and evaporation of volatile components. A liquid-phase sintering aid incorporating Cu2O and PbO is presented which demonstrates a reduction in the required sintering temperature of these ceramics. This new aid is described with particular reference to a commercial PZT, termed Pz26, used industrially for its optimised piezoelectric properties. Pz26 has a composition near the morphotropic phase boundary and possesses a tetragonal crystalline structure. Typically this material is sintered between 1260 and 1300°C for 1 h to achieve the required densification. With the inclusion of sintering aid, sintered densities comparable to those obtained by conventional sintering are achieved at only 800°C. The optimum weight percentage of sintering aid varies for different ceramic materials, particle sizes, morphology and the desired sintering temperature. However, with standard “mixed-oxide” produced Pz26 powder and with a median particle size in the range 1.6–1.7 μm, a value of 5 wt.% allows sintering at 800°C, according to densification, dielectric and piezoelectric measurements (ϵ=873, tan δ=1.13 %, kp=43.1%). When finer grained powder is used (d0.5=1.1 μm), improved properties (ϵ=960, tan δ=1.04%, kp=51.7%) are obtained for an addition of 3 wt.% sintering aid and a sintering temperature of 850°C.

Effects of addition of MnO on piezoelectric properties of lead zirconate titanate

Abstract: The effects of manganese addition on the piezoelectric properties, microstructure, sintering characteristic and Curie temperature have been studied for Pb(Zr,Ti)O3 (PZT) ceramics. The valence states of manganese are measured by Electron Spin Resonance (ESR). Those studies show that manganese coexist mainly in the way of Mn2+ and Mn3+ in PZT ceramics. When the concentration of Mn ion is below 0.5 mole%, it is preferentially incorporated in the lattice Pb site in Mn2+ or Mn3+, which gives rise to the increase of Kp and d33. In the intermediate concentration region of 0.5–1.5 mole%, Mn ion will be incorporated in the lattice of (Ti, Zr) site in Mn3+ acted as acceptor, which increases Qm without causing large changes of Kp and d33. When the concentration of Mn ion is larger than 1.5 mole%, it will accumulate at the grain boundaries and give rise to the decrease of piezoelectric properties of PZT ceramics. Small amount of Fe may decrease the solubility limit of Mn ion in PZT ceramics and it may also prevent the oxidation of Mn2+ and Mn3+.

Dielectric properties and field-induced phase switching of lead zirconate titanate stannate antiferroelectric thick films on silicon substrates

Abstract: Thick (∼5 μm) films of antiferroelectric compositions in the lead zirconate titanate stannate family of solid state solutions have been fabricated by sol–gel methods on platinum-buffered silicon substrates. Dielectric properties, electric field induced ferroelectric polarization, and associated elastic strain and the temperature dependence of the dielectric response have been explored as a function of composition. Films with high tin content are shown to undergo a diffuse antiferroelectric–paraelectric phase transition with temperature, probably because of compositional inhomogeneity associated with the high tin content. This type of film also demonstrates a diffuse field-induced antiferroelectric–ferroelectric phase switching under high electric field with the appearance of “slim loop” double hysteresis, which can be attributed to the compositional heterogeneity and the high level of tensile stress in the film because of the thermal mismatch between the film and substrate. On the other hand, the film wit...

Fabrication of Piezoelectric Ceramic/Polymer Composite Transducers Using Fused Deposition of Ceramics

Abstract: The fused deposition of ceramics (FDC) technique was used to fabricate piezoelectric ceramic skeletons for the development of piezoelectric composite transducers with 2–2 connectivity for medical imaging. The green parts were designed to have 30 vol% lead zirconate titanate ceramic (PZT-5H) in the final composites. Physical characterization of the sintered samples revealed that 96% of the theoretical density was achieved. Optical microscopy showed that defects due to the FDC mode of deposition, such as small roads and bubbles, were eliminated, because of improvements in powder processing. The electromechanical properties of the final composites were similar to the properties that were obtained for conventionally made composites. A matching layer and a backing layer, as well as wires and an inductor, were added to each FDC composite to fabricate a functional medical imaging transducer. The devices were tested in water using a steel target 3.5 cm thick. Echoes from the target could be detected with all the transducers that were fabricated using FDC. The sensitivities of the transducers were similar to that of a commercial transducer. However, the ringing was much longer than that for a commercial transducer, because the backing layer was not optimized in the transducers that were fabricated using FDC.

Studies of the ferroelectric domain configuration and polarization of rhombohedral PZT ceramics

Abstract: The character of the ferroelectric domains in lead zirconate titanate (PbZr1-x Tix O3 - PZT) ceramics has been studied using transmission electron microscopy (TEM) for compositions right across the rhombohedral phase (x = 0.06 to x = 0.45). The polarization hysteresis has also been determined for the same specimens and it has been demonstrated that the compositions between x = 0.12 and x = 0.40 show double hysteresis loops. It is shown that the occurrence of domain walls which do not correspond exactly to crystallographic planes produces generalized wedge-shaped domains, instead of the typical bands of parallel-sided domains reported in most ferroelectrics. A systematic variation in the arrangement of the domain walls as the composition progresses across the rhombohedral region is reported for the first time. This result is related to the occurrence of double hysteresis loops for these compositions. The role of oxygen octahedral tilts of the low temperature rhombohedral phase in the formation of the domains and in the hysteresis behaviour is discussed.

Influence of polarization orientation on the effective properties of piezoelectric composites

Abstract: The effective properties of 0–3- and 1–3-type piezoelectric composites of lead zirconate titanate and vinylidene fluoride–trifluoroethylene with different polarization status in both phases are calculated using an effective-medium theory. The effects of volume fraction and polarization orientation on the effective behavior are presented in detail. The theory gives results in reasonable agreement with recent experimental ones. The theoretical predictions demonstrate the interesting behavior of the composites and provide a general guideline for optimizing the microstructural scale of the composites for piezoelectric transducers and pyroelectric sensors.

Large piezoelectric effects in charged, heterogeneous fluoropolymer electrets

Abstract: Large piezoelectric d33 coefficients around 600 pC/N are found in corona-charged non-uniform electrets consisting of elastically “soft” (microporous polytetrafluoroethylene PTFE) and “stiff” (perfluorinated cyclobutene PFCB) polymer layers. The piezoelectric activity of the two-layer fluoropolymer stack exceeds the d33 coefficient of the ferroelectric ceramic lead zirconate titanate (PZT) by more than a factor of two and that of the ferroelectric polymer polyvinylidene fluoride (PVDF) by a factor of 20. Soft piezoelectric materials may become interesting for a large number of sensor and transducer applications, in areas such as security systems, medical diagnostics, and nondestructive testing.

Schottky barrier effects in the photocurrent of sol–gel derived lead zirconate titanate thin film capacitors

Abstract: We studied the photoresponse of Pb(Zr0.53Ti0.47)O3 (PZT) thin films by measuring the current–voltage (I–V) curve at several ferroelectric polarization states illuminated by a monochromatic 3.5 eV UV light. The photocurrent in Pt/PZT/Pt capacitors was sensitive to the polarization state, and the poling voltage-dependent photocurrent showed very asymmetric hysteresis behavior. The capacitance that is dependent upon the thickness of the samples was first measured. Then, the capacitance of the interfacial layer at a state with no interdiffusion between Pt and PZT film was extrapolated by using an equivalent circuit model. The result of the extrapolation was 28.1 μF/cm2.

Neutron Diffraction Studies of Pb(ZrxTi1-x)O3 Ceramics

Abstract: Neutron diffraction studies of lead zirconate titanate Pb(ZrxT1-x)O-3 (PZT) powders, 0.20 less than or equal to x less than or equal to 0.54, were carried out at 10 K and 297 K, The phase transitio ...

Sol–Gel Preparation of Lead Zirconate Titanate Powders and Ceramics: Effect of Alkoxide Stabilizers and Lead Precursors

Abstract: Lead zirconate titanate (PZT) (52/48) powders were prepared by a sol‐gel process, using different raw materials to introduce the lead component together with several solvents and chemical modifying agents. A study of the effect of these variables on crystallization behavior was conducted to determine the best conditions for preparing monophasic submicrometersized PZT perovskite powders in the morphotropic region. In the present work, well-crystallized, submicrometer-sized single-phase perovskite PZT powders were obtained after heat treatment at 600°C for 1 h. The dependence of this crystallization temperature on the preparation conditions was observed. The sol‐gel-derived submicrometer-sized PZT powders were sintered to ! 96% of relative density after 2 h at 950°‐970°C. The sintered ceramics exhibited a dielectric permittivity of 1000, a piezoelectric coefficient of 135 pC! N ! 1 , a remanent polarization of 20 " C! cm ! 2 , and a coercive field of 10.6 kV! cm ! 1 .

Domain nucleation and relaxation kinetics in ferroelectric thin films

Abstract: The time-dependent relaxation of the remanent polarization in epitaxial lead zirconate titanate (PbZr0.2Ti0.8O3) ferroelectric thin films, containing a uniform two-dimensional grid of 90° domains (c axis in the plane of the film), is examined using piezoresponse microscopy. The 90° domain walls preferentially nucleate the 180° reverse domains during relaxation, with a significant directional anisotropy. Relaxation occurs through the nucleation and growth of reverse domains, which subsequently coalesce and consume the entire region as a function of time.

Dielectric properties of lead zirconate titanate thin films deposited on metal foils

Abstract: Ferroelectric lead zirconate titanate (PZT) thin films deposited on metal foil substrates are suitable for developing a wide range of applications. In this letter, we report on PZT films deposited on a variety of foils, including titanium, stainless steel, brass, and nickel alloys, using sol–gel processing. The dielectric properties were shown to depend strongly on the foil material. Excellent properties for capacitors, including high dielectric constant (e=400), low dielectric loss (loss tangent of <5%), and low leakage current (below 5×10−8 A at 5 V) were obtained on titanium and good results were also obtained on other foils, such as stainless steel and brass foils. Also, excellent high-frequency properties were observed for capacitors on titanium, stainless steel, and brass foils.

Uniaxial stress dependence of the piezoelectric properties of lead zirconate titanate ceramics

Abstract: Piezoelectric transducers are often used under compressive stress in smart structure and other applications and it is therefore important to know properties of these materials as a function of applied stress. We have developed an experiment that allows us to find the piezoelectric charge coefficient as a function of uniaxial stress in the poled direction . Both dynamic and static measurements were carried out and the corresponding values of the charge coefficient d33 were obtained as a function of applied stress. These coefficients differ from each other because of the different proportions of reversible and irreversible domain changes that contribute to them and each coefficient can be important in specific applications. Results on a range of PZT ceramics manufactured by EDO Corporation are presented; in general, they show a non- linear behavior with an initial increase in d33 as the stress increases followed by a significant decrease. The time dependence of the measurement has also been investigated.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Single Element High Frequency (<50 MHz) PZT Sol Gel Composite Ultrasound

Abstract: A sol gel composite process has been used to produce lead zirconate titanate coatings in the thickness range of 3 to 100 pm on aluminum substrates. The complex permittivity (E&), elastic stiffness (cg), and the piezoelec- tric constant (h33) of the coating and the complex elastic stiffness (cz) of the substrate have been determined us- ing impedance measurements and a commercially available software program (Piezoelectric Resonance Analysis Pro- gram PRAP 2.0, TASI Technical Software, Kingston, On- tario, Canada). The complex components of the material parameters account for the losses within the film and the substrate. Sol gel composite films on aluminum have a di- electric constant of 220 with an imaginary component of 1% and an electromechanical coupling coefficient of up to 0.24 with an imaginary component of 3%. These films are applied to the fabrication of high frequency transducers suitable for ultrasound biomicroscopy (UBM). By combin- ing the sol gel composite material with existing transducer fabrication techniques, single-element focusing transducers have been produced that operate in the frequency range of 70 to 160 MHz. Devices have -6-dB bandwidths up to 52% and minimum insertion losses ranging from -47 to -58 dB. Real-time images of phantom materials and ex vivo biolog- ical samples are shown.

Piezoelectric and pyroelectric properties of PZT/P(VDF-TrFE) composites with constituent phases poled in parallel or antiparallel directions

Abstract: Composites of lead zirconate titanate (PZT) powder dispersed in a vinylidene fluoride-trifluoroethylene copolymer [P(VDF-TrFE)] matrix have been prepared by compression molding. Three groups of polarized samples have been prepared by poling: only the ceramic phase, the ceramic and polymer phases in parallel directions, and the two phases in antiparallel directions. The measured permittivities of the unpoled composites are consistent with the predictions of the Bruggeman model. The changes in the pyroelectric and piezoelectric coefficients of the poled composites with increasing ceramic volume fraction can be described by modified linear mixture rules. When the ceramic and copolymer phases are poled in the same direction, their pyroelectric activities reinforce while their piezoelectric activities partially cancel. However, when the ceramic and copolymer phases are poled in opposite directions, their piezoelectric activities reinforce while their pyroelectric activities partially cancel.

Actuation Properties of Lead Zirconate Titanate Thick Films Structured on Si Membrane by the Aerosol Deposition Method

Abstract: The results of the direct deposition of lead zirconate titanate [Pb(Zr0.52, Ti0.48)O3] (PZT) thick film on a Si-based structure are presented. The construction of a bottom electrode is very important for successful deposition. The actuation properties of PZT on the Si membrane were investigated. For a 6.2×6.1 mm2, 65-µm-thick Si membrane driven by a 4.7×4.3 mm2, 13-µm-thick PZT layer, the deflections, which were 1.5 µm upon applying 52 V at nonresonance frequency and 22 µm upon applying 8 V at resonance frequency, were measured.

Optical properties of PbZrxTi1−xO3 on platinized silicon by infrared spectroscopic ellipsometry

Abstract: A method of analyzing infrared spectroscopic ellipsometry (IRSE) measurement data is proposed for lead zirconate titanate PbZrxTi1−xO3 (PZT) thin films grown on Pt/Ti/SiO2/Si substrates with x=0.3 and 0.5. The IRSE data measured at an angle of incidence 75° for x=0.3 and 70° for x=0.5 are fitted by a dielectric function formula. The refractive index and extinction coefficient of PZT with x=0.3 and 0.5 are determined in the spectral range of 2.5–12.5 μm. As the wavelength increases, the refractive index decreases, on the contrary, the extinction coefficient increases. The absorption coefficient for x=0.5 is greater than that for x=0.3 by a factor of 1.5. The effective static ionic charges have also been derived, which are smaller than they would be in a purely ionic material for PZT thin films.

Single element high frequency (<50 MHz) PZT sol gel composite ultrasound transducers

Abstract: A sol gel composite process has been used to produce lead zirconate titanate coatings in the thickness range of 3 to 100 /spl mu/m on aluminum substrates. The complex permittivity (/spl epsi//sub 33//sup S/), elastic stiffness (c/sub 33//sup D/), and the piezoelectric constant (h/sub 33/) of the coating and the complex elastic stiffness (c/sub 33//sup D/) of the substrate have been determined using impedance measurements and a commercially available software program [Piezoelectric Resonance Analysis Program PRAP 2.0, TASI Technical Software, Kingston, Ontario, Canada]. The complex components of the material parameters account for the losses within the film and the substrate. Sol gel composite films on aluminum have a dielectric constant of 220 with an imaginary component of 1% and an electromechanical coupling coefficient of up to 0.24 with an imaginary component of 3%. These films are applied to the fabrication of a high frequency transducers suitable for ultrasound biomicroscopy (UBM). By combining the sol gel composite material with existing transducer fabrication techniques, single-element focusing transducers have been produced that operate in the frequency range of 70 to 160 MHz. Devices have -6-dB bandwidths up to 52% and minimum insertion losses ranging from -47 to -58 dB. Real-time images of phantom materials and ex vivo biological samples are shown.

Electrical fracture toughness for conductive cracks driven by electric fields in piezoelectric materials

Abstract: Fracture of piezoelectric materials can be caused by either mechanical loads or by electric fields. It is shown in lead zirconate titanate ceramics that conductive cracks driven by electric fields can be described by the same fracture mechanics concepts used for mechanical loads, but with a much higher fracture toughness. The electrical fracture toughness GICE=223.7±17.0 N/m (95% confidence) is 25 times higher than the mechanical fracture toughness GICM=8.7±0.4 N/m (95% confidence). This is due to the greater energy dissipation that is possible under electric loading but not possible under mechanical loading in the brittle ceramics of lead zirconate titanate.

Multisensor array of mass microbalances for chemical detection based on resonant piezo-layers of screen-printed PZT

Abstract: Original mass-microbalance sensors for gravimetric chemical detection are presented which are based on thickness-mode piezoelectric composite resonators made by lead zirconate titanate (PZT) films screen-printed on alumina substrate. By exploiting a cheap and affordable technology, such devices easily enable to manufacture gravimetric multisensor arrays on the same substrate. This is demonstrated by the presented four-sensor array manufactured on a 25×25 mm2 substrate, which also incorporates a thermostating element to minimize thermal drift. The resonators operate around 7 MHz and have a mass sensitivity in the order of 500 Hz/μg. The operating principle and sensor structure is described, and experimental results are reported relative to the sensors covered with purposely prepared polymeric coatings and exposed to hydrocarbon vapours (toluene and hexane) and SO2.

Theoretical and Experimental Study on Nanoscale Ferroelectric Domain Measurement Using Scanning Nonlinear Dielectric Microscopy

Abstract: We describe theoretical and experimental studies for nano-scale ferroelectric domain measurements using scanning nonlinear dielectric microscopy (SNDM). We calculate one-dimensional images of a 180° c-c domain boundary and show that SNDM has an atomic-scale resolution theoretically. Experimental results show that we measure the c-c domain on the lead zirconate titanate (PZT) thin film with the width of 1.5 nm and that the resolution of the microscope is less than 0.5 nm.

Surface bond contraction and its effect on the nanometric sized lead zirconate titanate

Abstract: The grain size effect of lead zirconate titanate PbZr1-x Tix O3 (PZT, x 0.6) caused by surface bond contraction has been investigated by using the Landau-Ginsburg-Devonshire (LGD) phenomenological theory. It has been shown that, due to the surface bond contraction, both the Curie temperature and the spontaneous polarization of tetragonal PZT decrease with decreasing grain size. These effects become more significant when the grain size is in the nanometre range. A dielectric anomaly appears with decreasing grain size, which corresponds to a size dependent phase transformation. The ferroelectric critical size below which a loss of ferroelectricity will happen is estimated from the results obtained.