Properties Of Lead Zirconate Titanate Ceramics Research Articles

Dielectric and piezoelectric properties of PLZT x/40/60 (x = 5; 12) ceramics

The paper presents the results of studies of the structure, piezoelectric and dielectric properties of lead zirconate-titanate ceramics modified with lanthanum of various concentrations (PLZT). It was found that with an increase in the La content, the grain size and the average domain size increase. The PLZT 12/40/60 samples contain both labyrinth-like and periodic domains, as well as different lateral sizes from several hundred nanometers to 3 microns in diameter. It was found that the piezoelectric response signal increases with increasing domain sizes in samples with a high lanthanum content. The fact of the existence of areas on surface of PLZT x/40/60 ceramics having an internal displacement field is established, as evidenced by the asymmetry of the remnant piezoelectric hysteresis loops along the voltage axis. In the samples PLZT 5/40/60 and PLZT 12/40/60, a significant dispersion of the permittivity ε(f) and a maximum of the tangent of the dielectric loss angle were observed in the frequency range from 105 to 106 Hz. This is due to the presence of ionic relaxation polarization, as is the case in ionic dielectrics. It is established that the value of the dielectric constant increases markedly with increasing La, which confirms the occurrence of a rigid unipolar state in the PLZT 12/40/60 ceramic grains. In the samples under study, an increase in the tangent of the dielectric loss angle is observed at low frequencies of the measuring field, which is associated with the contribution of conductivity to tg δ. The dependences of the dielectric loss factor ε” on the dielectric permittivity ε’are constructed. They have the form of Cole-Cole diagrams, which indicates the presence of a relaxation time spectrum, while it was found that the spectrum width in PLZT 5/40/60 samples is about two times less than in PLZT 12/40/60 samples.

Smart Energy Materials of PZT Ceramics

To better understand the material properties of lead zirconate titanate (PZT) ceramics, the domain-switching characteristics and electric power generation characteristics have been investigated during loading and unloading by using various experimental techniques. Furthermore, the influence of oscillation condition on the electrical power generation properties of lead zirconate titanate (PZT) piezoelectric ceramics has been investigated. It is found that the power generation is directly attributed to the applied load and wave mode. The voltage rises instantly to the maximum level under square-wave mode, although the voltage increases gradually under triangular-wave mode. After this initial increase, there is a rapid fall to zero, followed by generation of increasingly negative voltage as the applied load is removed for all wave modes. Variation of the electric voltage is reflected by the cyclic loading at higher loading frequencies. On the basis of the obtained experimental results for the wave modes, the electrical power generation characteristics of PZT ceramics are proposed, and the voltages generated during loading and unloading are accurately estimated. The electric generation value is decrease with increasing the cyclic number due to the material failure, e.g., domain switching and crack. The influence of domain switching on the mechanical properties PZT piezoelectric ceramics is clarified, and 90 degree domain switching occurs after the load is applied to the PZT ceramic directly. Note that, in this paper, our experimental results obtained in our previous works were introduced [1,2].

Characteristics of electrical power generation from lead zirconate titanatepiezoelectric ceramics under cyclic loading

The influence of oscillation condition on the electrical power generation properties of lead zirconate titanate (PZT) piezoelectric ceramics is investigated. It is found that the power generation increases with an increase of both applied load and load frequency. At lower loading frequencies, e.g., 0.1 and 0.5Hz, the voltage rises instantly to the maximum level under square-wave mode, although the voltage increases gradually under triangular-wave mode. After this initial increase, there is a rapid fall to zero, followed by generation of increasingly negative voltage as the applied load is removed for both wave modes. Variation of the voltage is reflected by the cyclic loading at higher loading frequencies, 15 and 30Hz. On the basis of the obtained experimental results for the two wave modes, the electrical power generation characteristics of PZT ceramics are proposed, and the voltages generated during loading and unloading are accurately estimated by numerical analysis.

Effect of domain wall characteristics on material properties of lead zirconate titanate piezoelectric ceramics

To better understand the material properties of lead zirconate titanate (PZT) ceramics, the influence of domain wall characteristics on the electrical and mechanical properties of PZT ceramics has been investigated. To obtain various domain wall characteristics, the poling process was carried out with different patterns with respect to the PZT ceramic. The domain walls were aligned in the PZT ceramic in the direction perpendicular to the poling direction. Such domain wall characteristic produced different crack growth behaviours. The crack growth occurred mainly along the domain walls of {110} for a31 (crack growth direction perpendicular to the poling direction) because of the high stress concentration between the domain walls. In contrast, the crack propagated along both domain walls and grain boundaries for a33 (crack growth direction parallel to the poling direction), leading to high crack growth resistance and good mechanical properties. The fracture toughness KIC values for the PZT ceramics in the a31 and a33 directions were about 0·5 and 2·6 MPa m1/2 respectively. It also appeared that the domain walls collapsed when a number of poling processes are conducted along different directions. These PZT ceramics had high mechanical properties due to the low stress concentrations.

Influence of domain orientation on the mechanical properties of lead zirconate titanate piezoelectric ceramics

The influence of domain orientation on the mechanical properties of lead zirconate titanate (PZT) piezoelectric ceramics has been investigated using un-poled and poled PZT ceramics. High mechanical properties, e.g., high elastic modulus and compressive strength, were obtained for the polarized PZT ceramics due to strain hardening caused by more severe domain switching during the loading process, while low mechanical properties for the un-poled ceramics. Fracture mechanics of the ceramics were influenced by the direction of the tetragonal lattice structure since cracks propagate along the long axis of the tetragonal structure ( c-axis). Using X-ray diffraction and electron back scatter diffraction analysis, the domain switching characteristics could be clarified.

A role of BNLT compound addition on structure and properties of PZT ceramics

In this research, effects of lead-free bismuth sodium lanthanum titanate (BNLT) addition on structure and properties of lead zirconate titanate (PZT) ceramics were investigated. PZT ceramics with addition of 0.1–3.0 wt%BNLT were fabricated by a solid-state mixed oxide method and sintering at 1050–1200 °C for 2 h to obtain dense ceramics with at least 96% of theoretical density. X-ray diffraction indicated that complete solid solution occurred for all compositions. Phase identification showed both tetragonal and rhombohedral perovskite structure of PZT with no BNLT phase detected. Scanning electron micrographs of fractured PZT/BNLT ceramics showed equiaxed grain shape with both transgranular and intergranular fracture modes. Addition of BNLT was also found to reduce densification and effectively limited grain growth of PZT ceramic. Optimum Hv and K IC values were found to be 4.85 GPa and 1.56 MPa.m 1/2 for PZT/0.5 wt%BNLT sample. Among PZT/BNLT samples, room temperature dielectric constant seemed to be improved with increasing BNLT content. The maximum piezoelectric coefficient values were observed in pure PZT ceramic and were slightly decreased in BNLT-added samples. Small reduction of remanent polarization and coercive field in hysteresis loops was observed in BNLT-added samples, indicating a slightly suppressed ferroelectric interaction in this material system.

In situ measurement of material properties of lead zirconate titanate piezoelectric ceramics during cyclic mechanical loading

To better understand the material properties of lead zirconate titanate (PZT) ceramics, in situ mechanical and electrical properties have been investigated continuously during cyclic mechanical loading. The material properties are demonstrated to change as a function of applied maximum stress, with the effective elastic constant increasing with increase of the stress level. The increase of effective elastic constant is attributed to the domain structure of the PZT. 90° domain switching can occur anywhere in the sample, which makes the strain accumulate and leads to high values of the effective elastic constant. The domain switching characteristics are clearly revealed by electron back scattered diffraction analysis. The changes of the electrical properties (electromechanical coupling coefficient, piezoelectric constant and permittivity) are in the opposite sense because of the material strain (or material damage), caused by the change of domain orientation; the electrical properties are degraded with increasing cycle number and applied stress. Based upon the variation of the material properties, details of the damage characteristics in the PZT ceramics are discussed.

Experiments and first principles calculations on the effects of hydrogen on the optical properties of ferroelectric materials

The effects of hydrogen on the optical properties of lead zirconate titanate (PZT) ceramics and BaTiO3 single crystals have been investigated. The experimental results showed that the color of BaTiO3 single crystals changed from light to dark after charging of hydrogen in NaOH solution at room temperature and in H2 gas at high temperature, and then, restored to light color after outgassing in the air, which were the same as PZT-5H ceramics reported earlier. Measurement of the absorbance indicated that hydrogen increased the absorbance within the visible spectrum for both PZT ceramics and BaTiO3 single crystals. The first principles calculations for Pb(Zr0.5Ti0.5)O3 and BaTiO3 showed that hydrogen increased the absorbance within the infrared and visible spectral region and the absorbance increased with the rise of hydrogen concentration. Density of states (DOS) researches indicated that hydrogen changed the DOS of the outer shell electrons, which caused the change of absorbance spectrum.

Influence of La2O3, SrO, and ZnO Addition on PZT

Effect of ZnO, SrO, and La2O3 additions on properties of lead zirconate titanate (PZT) nanopowder were investigated. Our objective was to densify PZT near 900°C to reduce lead loss and increase processing compatibility of these materials with IC fabrication technique for micro‐electro‐mechanical systems (MEMS). PZT nanopowders were synthesized using citrate nitrate autocombustion method. ZnO was used as sintering aid, which promoted liquid phase sintering. With only 2 wt% ZnO addition, 93% theoretical density was achieved after sintering at 900°C for 1 h. SrO and La2O3 were used as A‐site dopants in PZT to improve dielectric properties. Different amounts of SrO, La2O3, and a combination of both were added in 2 wt% ZnO‐doped PZT. Between 93% and 95% of theoretical densities were obtained in all cases after sintering at 900°C for 1 h. X‐ray diffraction analysis revealed that increase in SrO content increased tetragonal phase formation. However, addition of La2O3 stabilized both tetragonal and rhombohedral phases. Increase in SrO content increased the dielectric constant of PZT with a maximum dielectric constant of 1800 for 1 wt% SrO and 2 wt% ZnO sample. It was observed that an increase in La2O3 up to 2 wt% increased dielectric constant, and the highest dielectric constant obtained was 1500. Combination of both SrO and La2O3 addition showed even higher dielectric constant than their individual contribution. Highest dielectric constant of 2100 was measured for 2 wt% La2O3, 1 wt% SrO and 2 wt% ZnO‐doped PZT which was sintered at 900°C for 1 h. This is one of the highest dielectric constant reported for PZT ceramics that was sintered below 1000°C.

Aqueous colloidal processing and green sheet properties of lead zirconate titanate (PZT) ceramics made by tape casting

An aqueous system for tape casting PZT ceramics was developed using poly (vinyl alcohol) binder, poly (propylene glycol) plasticizer, D3021 dispersant and Surfynol SE-F wetting agent. Screening experiments were performed to assess the stability of the suspension in the presence of the dispersant by performing pH, conductivity and Zeta potential measurements. Viscosity measurements were used to find the optimum level of dispersant needed to produce a stable slip at pH 10.2. Subsequently, the rheological and mechanical characteristics were also investigated.

Nonlinear properties of lead zirconate–titanate piezoceramics

Nonlinear properties of lead zirconate-titanate (PZT) piezoceramics are investigated using ultrasonic second harmonic generation technique. When a sinusoidal ultrasonic wave of frequency ω0 is sent into a nonlinear material, the second harmonic wave with frequency 2ω0 is generated. Through measuring the absolute amplitude of the fundamental (ω0) and of the second harmonic (2ω0) waves, the ultrasonic nonlinearity parameter β can be determined, which involves certain combinations of the third-order elastic constants and piezoelectric coefficients. We report the measured nonlinear parameters for four types of doped PZT ceramics, PZT-4, PZT-5A, PZT-5H, and PZT-5H HD, which are widely used in practice. We found that the nonlinear parameter is much more sensitive than the linear parameter in responding to microstructural changes in piezoceramics. It could be used to distinguish unpoled samples from depoled samples, which are undistinguishable in terms of the linear parameters.

Effect of Pb/(Zr+Ti) molar ratio on the photovoltaic properties of lead zirconate-titanate ceramics

Lead zirconate-titanate ceramics having various Pb/(Zr+Ti) molar ratios ranging from 0·90 to 1·01 and a fixed Zr/Ti molar ratio of 50/50 have been sintered at 950–1250°C for 2 h to investigate the change in photovoltaic properties, as well as their grain size dependence on ultraviolet irradiation. The photovoltaic current increased abruptly when the molar ratio was less than 1·00, whereas the photovoltage gave scattered results and decreased between the molar ratio of 0·99 and 1·00, which was caused by grain growth. The maximum output power discernibly increased, confirming a net increase in photovoltaic efficiency. The grain size dependence of the photovoltage revealed an opposite tendency in two samples with different molar ratios of 0·992 and 1·00. From these results, it is proposed that creating Pb vacancies on the perovskite lattice is essential for the photovoltaic properties of the samples.

Effect of multiple impurity doping on the photovoltaic properties of lead zirconate-titanate ceramics

Pb(Zr0.5, Ti0.5)O3 (PZT) ceramics singly doped with 0-3 mol% of Ta and those multiply doped with 1 mol% of Na and 0-4 mol% of Ta have been sintered at 1050-1300 °C for 2h to investigate the change in photovoltaic properties with changes in the concentration of Pb vacancies, and also grain size, upon ultraviolet irradiation. Both photovoltaic current and photovoltage were markedly increased by the doping of Ta in the case of single doping, whereas in the multiply doped samples they showed no significant change up to 1 mol% of doped Ta. Beyond this amount, however, they were found to significantly increase. The average grain size in the singly doped samples decreased with increasing amounts of doped Ta, while that in the multiply doped samples revealed a maximum at around 1 mol% Ta, below which grain size was smaller than that of the nondoped sample. It is concluded from these results that the formation of Pb vacancies onto the perovskite lattice, rather than the existence of doped Ta, has a fundamental significance on the photovoltaic properties in PZT ceramics

Sintering Model for Mixed‐Oxide‐Derived Lead Zirconate Titanate Ceramics

The properties of lead zirconate titanate (PZT) ceramics are determined by the microstructure and chemical homogeneity of Zr, Ti, and dopants within the grains as well as the presence of secondary grain boundary phases. Stoichiometric 53/47 PZT and compositions with 3 mol% PbO excess were prepared by the mixed‐oxide process, and were densified by pressureless sintering in oxygen. The influence of PbO content and different La concentrations on the densification behavior was analyzed by dilatometric measurements. Quantitative image analysis showed a different relative density and grain size dependence for samples containing >0.5 mol% additives compared to samples with <0.5 mol% La. On the basis of a model experiment and by using different analytical methods (microprobe analysis, HRTEM, STEM, and Auger spectroscopy) three types of inhomogeneities could be detected in conventionally prepared PZT ceramics: the existence of Ti and La enrichment in the core of PZT grains, and PbO‐rich secondary phases in triple junctions as well as in grain boundary films. The results of the microstructural characterization and the analysis of the densification behavior were finally combined to deduce a sintering model based on a Pb‐vacancy concentration gradient within the PZT grains.

Ultrasonic nonlinear properties of lead zirconate-titanate ceramics

A systematic study of the nonlinear properties of lead zirconate-titanate (PZT) ceramics is presented. The velocity, attenuation, and nonlinearity parameter of PZT ceramics were measured from room temperature to temperatures above the Curie temperature. The velocity goes through a minimum near the Curie temperature. In spite of a maximum in attenuation near the Curie temperature, the nonlinearity parameter exhibits a maximum whose behavior is affected by polarization. Frequency dependence of the nonlinearity parameter at room temperature is reported for the first time. Large third harmonics of an initially sinusoidal ultrasonic wave at room temperature suggest that either the effect of the fourth-order elastic constants is anomalously large or that the nonlinear equation used to describe the behavior of single crystals is only approximately valid for description of PZT. Strain gradients are assumed to cause the frequency dependence of the nonlinearity parameter as well as the large third harmonic.

Effects of impurity doping in lead zirconate-titanate ceramics

Abstract Impurity doping effects on the properties of lead zirconate-titanate ceramics have been investigated from the internal bias field viewpoint. The internal bias field is strengthened by doping with single or multiple acceptors, but is weakened by single or multiple donors. Equimolar mixed acceptor and donor dopants have no influence on the internal bias field. These facts suggest that the internal bias field is caused by complexes of acceptor atoms and oxygen vacancies. The internal bias field gives rise to effects on the domain wall motions. It prohibits the poling process, increases the mechanical quality factor and accelerates the aging change in the frequency constant. The mechanical quality factor and the aging change are proportional to the internal bias field. However, when the internal bias field reorients itself parallel to the spontaneous polarization in a short time after poling, the aging change becomes small, even for a specimen having a strong internal bias field.

Internal Bias Field Effects in Lead Zirconate-Titanate Ceramics Doped with Multiple Impurities

The effects of doping with multiple impurities on the electromechanical properties of lead zirconate-titanate ceramics have been investigated from the viewpoint of the internal bias field. The internal bias field is strengthened by doping with the multiple acceptors K and Fe, but weakened by the multiple donors La and Nb. Simultaneous doping with donor and acceptor prevents the field from being enhanced by the latter. These facts suggest that the internal bias field is caused by a complex of an acceptor impurity and an oxygen vacancy. The properties of ceramics can be varied by controlling this field, and the mechanical quality factor and the aging change in the frequency constant are proportional to it.

The grain dependence of the electromechanical properties in lead zirconate-titanate ceramics: Webster, A.H., Weston, T.B., Journal of the Canadian Ceramic Society, Vol 37 (1968) pp XLI-XLV

In this paper, we report a novel piezoelectric artificial cochlea which realizes both acoustic/electric conversion and frequency selectivity without an external energy supply. The device comprises an artificial basilar membrane (ABM) which is made of a 40 μm thick polyvinylidine difluoride (PVDF) membrane fixed on a substrate with a trapezoidal slit. The ABM over the slit, which mimics the biological system, is vibrated by acoustic waves and generates electric output due to the piezoelectric effect of PVDF. The width of ABM is linearly varied from 2.0 to 4.0 mm along the longitudinal direction of 30 mm to change its local resonant frequency with respect to the position. A detecting electrode array with 24-elements of 0.50 × 1.0 mm rectangles is made of an aluminum thin film on ABM, where they are located in a center line of longitudinal direction with the gaps of 0.50 mm. Since the device will be implanted into a cochlea filled with lymph fluid in future, the basic characteristics in terms of vibration and acoustic/electric conversion are investigated both in the air and in the silicone oil which is a model of lymph fluid. The in vitro optical measurements show that the local resonant frequency of vibration is varied along the longitudinal direction from 6.6 to 19.8 kHz in the air and from 1.4 to 4.9 kHz in the silicone oil, respectively. Since a resonating place vibrates with relatively large amplitude, the electric output there becomes high and that at the other electrodes remains to be low. Thus, the electric voltages from each electrode realize the frequency selectivity. Furthermore, the effect of surrounding fluid on the vibration is discussed in detail by comparing the experimental results with the theoretical predictions obtained by the Wentzel–Kramers–Brillouin asymptotic method. The theoretical prediction indicates that the surrounding fluid of the higher density induces the larger effective mass for the vibration that results in lower resonant frequency. From these findings, the feasibility of artificial cochlea is confirmed both experimentally and theoretically.

Effect of PbO Deficiency on the Piezoelectric Properties of Lead Zirconate‐Titanate Ceramics

Effect of PbO Deficiency on the Piezoelectric Properties of Lead Zirconate‐Titanate Ceramics