Soft PZT Ceramics Research Articles

Revealing multiphase coexistence of R-O-T phases in BaTiO3-CaTiO3-BaSnO3 electroceramics for energy harvesting and storage response with piezo actuation

The (Ba1-xCax)(SnyTi1-y)O3 piezoelectric ceramics (where x=0.016, y=0.024; x=0.032, y=0.048; x=0.048, y=0.072; x=0.064, y=0.096; x=0.08, y=0.12) were designed by conventional solid state reaction method. The crystal structure for the composition of x=0.064 and y=0.096 (abbreviated as BCST-4) possesses the coexistence of non-centrosymmetric rhombohedral-orthorhombic-tetragonal (R-O-T) tri-lattice symmetries at room temperature, as demonstrated by the structural Rietveld refinement, Raman analysis, and temperature dependence of dielectric study. Because of the R-O-T multiphase coexistence, BCST-4 possesses a superior electromechanical and piezoelectric property viz. kp ∼ 0.45, strain ∼ 0.100 %, d33* ∼ 649 pm/V, and an improved d33 ∼ 452 pC/N, which is comparable to commercially available soft PZT ceramics (d33 ⁓ 370 pC/N). For BCST-4 ceramics, an exceptional electrostriction coefficient Q33 ∼ 0.0434 m4/C2 value was attained. The intrinsic piezo-actuation DC strain was observed to be 130 microstrain (με) and 188 με with ε33 and ε31 modes respectively. The BCST-4 ceramic exhibits a maximum output power of 1.03 mW, a power density of 13.5 µW/mm3, a maximum output current of 88 µA, and an open circuit voltage Vpp of 28 V which successfully glowed ‘SPPU’ panel having 40 red commercial light-emitting diodes (LEDs). The energy storage study reveals that BCST-4 ceramics exhibit a maximum energy storage density (Wrec) of 165.87 mJ/cm3 with efficiency (ƞ) 68.00 %. Therefore, the improvement in electrostriction coefficient, piezoelectric charge coefficient, and energy storage response indicates that BCST-4 ceramic has the potential for actuator, energy harvesting, and energy storage applications.

Properties of the surface layer of ferroelectric ceramics

In this article, we study the features of the surface layer formed during mechanical treatment of the sample surface of hard and soft PZT ceramics. We have compared the properties of the surface layer induced by polishing for hard and soft ferroelectric ceramics. For both ceramics, a correlation between microhardness and domain size has been found. It has been shown that the properties of the surface layer formed in ferroelectric ceramics depend on the particle size of the diamond paste used in polishing.

Experimental and Theoretical Investigations of Electromagnetic Radiation Emission from Soft and Hard PZT Ceramics

Electromagnetic radiation (EMR) signals from soft (SP 5A) and hard (SP 4) PZT ceramics under the influence of alternating electric fields have been investigated. The 180° oscillations of dipoles present in the piezoelectric ceramics give rise to EMR voltage signals. The soft PZT shows higher EMR signals as compared to the hard PZT which is due to the ease in the movement of dipoles in the soft PZT because of the existing vacancies which is its characteristic feature. On the other hand, the hard PZT having no vacancies does not allow that much free movement of dipoles under the effect of the external stimulus. The EMR signals have been measured using the non-contact detection technique in which an annular antenna made up of copper was placed around the samples to obtain the EMR signals which were measured during the application of an alternating electric field on the samples. The effect of frequency has been experimentally explored and it has been observed that the EMR signal increases with the increase in the frequency of the applied alternating electric field due to the increase in the frequency of oscillations of the dipoles. When the EMR voltage is measured with increasing distance from the sample, it shows the decaying pattern which matches the pattern with which electromagnetic radiations fall off with distance. The results from the analytical model are in agreement with the experimental results. These materials and measurement technique show their potential for wireless sensing applications using piezoelectric materials which have the potential to replace the currently used wired sensors.

Electric behaviour of soft and hard lead zirconate titanate ceramics under electromechanical loading

ABSTRACTThe influence of uniaxial pressure (0 –1100 bars) applied parallel to the ac and dc electric field on the dielectric and ferroelectric properties of soft and hard PZT ceramics was studied in the temperature range from room temperature to 500°C. The results show that applying uniaxial pressure leads to a reduction of the peak intensity of the electric permittivity (ε) and its frequency dispersion. The peak intensity of ε becomes diffused and shifts with increasing pressure. The effective electric field Eeff and electrostrictive coefficient Q11 were evaluated from the obtained data. We explained our results based on the Cochran soft-mode, dielectric relaxation and a combination of de-aging and domain resulting processes from pressure.

Ferroelectric studies for soft Gd-modified PZT ceramics

ABSTRACTThe polycrystalline samples of gadolinium-modified lead–zirconate–titanate (Pb1−xGdx (Zr0.52Ti0.48)1−x/4O3) (x = 0, 0.07, 0.10 and 0.12) (PGZT x/52/48) ceramics near morphotropic-phase boundary were prepared using conventional solid-state reaction route. XRD patterns show the formation of single-phase compounds in rhombohedral crystal system. SEM textures of the samples reveal uniform grain distribution. Frequency and temperature dependence of dielectric constant of the materials indicates non-relaxor behavior and indication of the diffuse phase transition at higher values of Gd concentration. The temperature dependence of P–E loops confirms ferroelectricity in the materials. The piezoelectric studies of the samples show enhancement in piezoelectric coefficients on substitution of Gd at the Pb site.

The effect of temperature and loading frequency on the converse piezoelectric response of soft PZT ceramics

The converse piezoelectric coefficient d33 of soft PZT ceramics was measured from 20 °C to 150 °C under different loading frequency. Results showed that in the tested temperature range, the evolution of d33 obeys the Rayleigh-law behavior. The influence of temperature on d33 is a little complicated. For instance, the maximum d33 was observed at 150 °C when the applied electric field E was at 0.1 kV mm−1. When E increased to 0.3 kV mm−1 and 0.4 kV mm−1, the maximum d33 was observed at 120 °C and 100 °C, respectively. Such behaviors are rationalized by the evolution of the Rayleigh parameters dinit and α. For dinit, it increases as temperature increases. While for α, it first increases and then decreases with the increase of temperature due to the evolution of the spontaneous strain and the volume of the switched domains. In the tested loading frequency, d33 decreased linearly with the logarithm of the frequency of electric field. With the increase of temperature, the influence of frequency on d33 gradually weakened, implying that at high temperature, the motion of domain walls became active and the pinning effect of defects nearly disappeared.

Effects of temperature on aging degradation of soft and hard lead zirconate titanate ceramics

Abstract This paper aims to study the effects of heat treatment temperatures on the aging degradation of piezoelectric properties, i.e. piezoelectric coefficient ( d 33 ) and planar electromechanical coupling factor ( k p ), in soft and hard PZT ceramics. Aging degradations of d 33 and k p of the samples were measured for 192 h prior to heat treatments. The samples were then treated at various temperatures equivalent to 0.3, 0.4, 0.5, 0.6, 0.7 and 0.8 times of the materials' Curie temperatures. Aging degradations of d 33 and k p of the heat-treated samples were observed continuously for 1128 h. The piezoelectric properties of the un-treated samples gradually decreased with aging time. Attenuation of d 33 and k p in the samples immediately after heat treatment increased with increasing heat treatment temperature. Moreover, aging degradation rate and relaxation time of the samples measured after heat treatments increased with increasing heat treatment temperature. Comparing to hard PZT ceramics, soft PZT demonstrated greater change of d 33 and k p immediately after heat treatments. Soft PZT also showed greater aging rate and aging time than those of hard PZT. From the overall results, it can be concluded that both material type and heat treatment temperature have effects on aging behaviors of PZT materials. Aging degradation was more pronounced in soft PZT and the samples treated at high temperatures. The observed aging behaviors of PZT materials were explained by the interaction between domains and defects of oxygen vacancies that leads to volume, domain and grain boundary effects.

Dielectric and Piezoelectric Properties of “Lead-free” Piezoelectric Rhombohedral Ba(Ti0.92Zr0.08)O3 Single Crystals

Rhombohedral Ba(Ti 0.92 Zr0.08)O₃ single crystals are fabricated using the cost-effective solid-state single crystal growth (SSCG) method; their dielectric and piezoelectric properties are also characterized. Measurements show that (001) Ba(Ti 0.92 Zr 0.08 )O₃ single crystals have an electromechanical coupling factor (k 33 ) higher than 0.85, piezoelectric charge constant (d 33 ) of about 950 [pC/N], and piezoelectric voltage constant (g 33 ) higher than 40 [x10 -3 Vm/N]. Especially the d 33 of (001) Ba(Ti 0.92 Zr 0.08 )O₃ single crystals was by about six times higher than that of their ceramics. Because their electromechanical coupling factor (k 33 ) and piezoelectric voltage constant (d 33 , g 33 ) are higher than those of soft PZT ceramics, it is expected that rhombohedral (001) Ba(Ti 0.92 Zr 0.08 )O₃ single crystals can be used as “lead-free” piezoelectric materials in many piezoelectric applications such as actuator, sensor, and transducer.

Creep behavior of soft and hard PZT ceramics during mechanical loading and unloading

The creep behavior of strain and electrical polarization in two poled PZT with different compositions was investigated during stress loading and unloading. Being different from the standard testing methods, the creep behaviors at all stress levels were characterized using a single sample, rather than a fresh sample at each load level. During loading, the creep of polarization and strain are observed at higher stress than that in soft PZT due to the effect of internal bias field. During unloading, significant recovery of strain and polarization was observed in the hard PZT, demonstrating that a compressive stress of 380MPa cannot reorient the ordered defect dipoles in Fe doped hard PZT. Two equations P0.5=α1log(t+t0)+β1 and Screep0.5=a2log(t+t0)+β2Screep0.5=a2 log(t+t0)+β2 were summarized to describe the creep polarization and the creep strain, respectively. Compared with the conventional power law creep equations, the two equations can fit the experimental results well in the whole range of stress holding.

0.8 이상의 전기기계결합계수(k33)를 가지는 고효율 무연 압전 Ba(Ti0.94Zr0.06)O3단결정

Orthorhombic Ba(Ti 0.94 Zr 0.06 )O₃ single crystals are fabricated using the cost-effective solid-state single crystal growth (SSCG) method; their dielectric and piezoelectric properties are also characterized. Measurements show that (001) Ba(Ti 0.94 Zr 0.06 )O₃ single crystals have an electromechanical coupling factor (k 33 ) higher than 0.83, piezoelectric charge constant (d 33 ) of about 400 [pC/N], and piezoelectric voltage constant (g 33 ) higher than 50 [x10 -3 Vm/N]. The transition temperature (TOT) of the (001) Ba(Ti 0.94 Zr 0.06 )O₃ single crystals between orthorhombic and tetragonal phases is also observed to be about 61℃. Because their electromechanical coupling factor (k 33 ) and piezoelectric voltage constant (g 33 ) are higher than those of soft PZT ceramics, it is expected that (001) Ba (Ti 0.94 Zr 0.06 )O₃ single crystals can be used as “lead-free” piezoelectric materials in many piezoelectric applications.

Subcritical Crack Growth in Unpoled and Poled PZT Ceramics under Applied Static and Oscillating Electric Fields. I. Experimental Observation

The effects of both electric field and mechanical stress on the subcritical crack growth (SCG) behavior of lead zirconate titanate (PZT) ceramics are investigated. In Part I, the growth of indented crack in unpoled and poled soft PZT ceramics subjected to different static and oscillating electric fields is studied. The experimental results indicated a faster crack growth rate initially followed by a slower growth rate with time. The SCG behaviors along directions perpendicular and parallel to the applied electric fields are different and depend on the field intensity, field polarity, frequency, and wave-form of the applied oscillating fields. It is suggested that the crack driving forces for the SCG behavior in PZT ceramics are due to the residual stress from indentation and the application of the electric field.

Ferroelectric Dipole Electrets Prepared from Soft and Hard PZT Ceramics in Electrostatic Vibration Energy Harvesters

Aiming at longer stability of surface potential, we propose a ferroelectric dipole electret (FDE) prepared from hard ferroelectric material. We compared output power of electrostatic vibration energy harvester and surface potential stability between FDEs prepared from soft and hard PZT ceramics, as well as a CYTOP polymer electret. The hard FDE showed a seven-fold increase in output power over the soft FDE and nine-fold increase over the CYTOP polymer electret. The hard FDE also showed longer stability of surface potential than that of the soft FDE, whereas the stability of the hard FDE was not yet comparable to that of CYTOP polymer electret. A FDE prepared from harder PZT ceramic (with higher coercive electric field and Curie temperature) may provide more stability in surface potential.

Temperature‐dependent ferroelectric dynamic hysteresis properties of modified PMN–PZT relaxor ceramics

AbstractTemperature‐dependent ferroelectric dynamic hysteresis properties of modified Pb(Mg1/3Nb2/3)O3–Pb(Zr,Ti)O3 (PMN–PZT) ceramics have been investigated in a wide range from 298 to 433 K. Interestingly, it was found that back‐switching polarization Pbc increased while the hysteresis area 〈A 〉, coercive field Ec, saturation polarization Ps, and remnant polarization Pr all decreased linearly with temperature below 398 K (close to the macro–micro domain transition temperature Tnr). A set of simple linear temperature scaling relations was established, which is different from the power‐law scaling relations for soft and hard PZT ceramics. At further increased temperature, double‐loop features appeared and the ferroelectric properties varied nonlinearly due to the reversible macro–micro domain transition in the T > Tnr region. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Linear temperature scaling of ferroelectric hysteresis in Mn-doped Pb(Mn1/3Sb2/3)O3-Pb(Zr,Ti)O3 ceramic with internal bias field

The temperature scaling of dynamic hysteresis was investigated in Mn-doped Pb(Mn1/3Sb2/3)O3-Pb(Zr,Ti)O3 ceramic with internal bias field. A set of simple linear temperature scaling relations were established for hysteresis area 〈A〉, coercivity Ec, and internal bias field Ei, which are different from the power-law scaling relationships for the soft and hard PZT ceramics. The proposed scaling relation between 〈A〉 and T can be predicted by the temperature dependent response of Ec and vice versa. It is suggested that the thermal deaging which related to the redistribution of the preferentially oriented defect dipoles is responsible for these dynamic hysteresis behaviors.

The effects of aliovalent cations doping on electric-field-induced strain and microstructures of (Bi0.5Na0.5)0.94Ba0.06TiO3 lead-free piezoceramics

Effects of Al and Nb doped (Bi0.5Na0.5)0.94Ba0.06TiO3(abbreviated as BNB6T) ceramics on dielectric, ferroelectric, and strain properties were investigated. The results indicated that the d33⁎ value is significantly higher in pure BNB6T ceramics than in Nb doped BNB6T and Al doped BNB6T ceramics, and that S–E curve for the Al doped BNB6T ceramics displayed a typical W-shaped butterfly curve, but pure BNB6T and Nb doped BNB6T ceramics display a V-shaped curve. The P–E loops for pure BNB6T and Nb doped BNB6T ceramics were similar to soft PZT ceramics with slim profiles. According to the results of microstructures analysis, significant strain may originate from the development of the optimum compound domains coexistence (the mixture of microdomain and nanodomain), which provide large saturation polarization and low-energy barrier dipole switching under an applied electric field. All these would provide a new concept for lead-free ceramics to realize high strain response for practical applications in actuator or other piezoelectric devices.

Gigantic Electrostrain in Duplex Structured Alkaline Niobates

We demonstrate that an exceptionally large strain can be induced in CaZrO3-modified alkaline-niobates by electric fields. The maximum induced strain of our niobate-based ceramics could reach more than 1,000 pm/V, which is a much higher value than that of commercial soft PZT ceramics. Atomic-scale annular bright-field (ABF) and annular dark-field (ADF) scanning transmission electron microscopy (STEM) directly revealed that individual single grains were composed of an electrically duplex core–shell structure; relaxor-like cores and paraelectric shells. Based on this ABF STEM analysis along with electrical measurements, a plausible mechanism explaining the high strain effect in the present work was suggested. This new material offers an unprecedented opportunity to produce efficient Pb-free piezoelectrics for applications that require large electrostrictive motion.

Soft and hybrid-doped Pb(Zr,Ti)O3 ceramics under stress, electric field, and temperature loading

We investigated the influence of uniaxial pressure (0–1000 bars) applied parallelly or perpendicularly to the ac or dc electric field (in a one-dimensional or two-dimensional manner) on dielectric and ferroelectric properties of selected soft and hybrid-doped PZT ceramics (1 mol. % Gd, 1 mol. % La and 1 mol. % (La+Fe)-doped Pb(Zr0.54Ti0.46) O3). Applying uniaxial pressure leads to a reduction of the peak intensity of the electric permittivity (ɛ), of the frequency dispersion, and of the dielectric hysteresis. The peak intensity of ɛ becomes diffused and shifts to a higher temperatures with increasing pressure. Simultaneous application of uniaxial pressure and dc electric field (perpendicular to each other) in the poling process implies in improvement of the ferroelectric properties, indicating a new possibility for poling materials with a high coercive field and/or high electric conductivity. It was also found that simultaneous application of uniaxial pressure and dc electric field (perpendicular to each other) allowed observation of the space charge in the depolarization process. The electrostrictive coefficient Q11 and differential permittivity were evaluated from obtained data. Our results show that applying uniaxial pressure induces similar effects as increasing the Ti-ion concentration in the PZT system. We interpreted our results based on the Cochran soft-mode and domain switching processes under the action of pressure.

Effect of electrical and mechanical poling history on domain orientation and piezoelectric properties of soft and hard PZT ceramics

The superior piezoelectric properties of all polycrystalline ferroelectrics are based on the extent of non-180° domain wall motion under electrical and mechanical poling loads. To distinguish between 180° and non-180° domain wall motion in a soft-doped and a hard-doped lead zirconate titanate (PZT) ceramic, domain texture measurements were performed using x-ray and neutron diffraction after different loading procedures. Comparing the results to measurements of the remanent strain and piezoelectric coefficient allowed the differentiation between different microstructural contributions to the macroscopic parameters. Both types of ceramic showed similar behavior under electric field, but the hard-doped material was more susceptible to mechanical load. A considerable fraction of the piezoelectric coefficient originated from poling by the preferred orientation of 180° domains.

Effect of electrical and mechanical poling history on domain orientation and piezoelectric properties of soft and hard PZT ceramics

The superior piezoelectric properties of all polycrystalline ferroelectrics are based on the extent of non-180° domain wall motion under electrical and mechanical poling loads. To distinguish between 180° and non-180° domain wall motion in a soft-doped and a hard-doped lead zirconate titanate (PZT) ceramic, domain texture measurements were performed using x-ray and neutron diffraction after different loading procedures. Comparing the results to measurements of the remanent strain and piezoelectric coefficient allowed the differentiation between different microstructural contributions to the macroscopic parameters. Both types of ceramic showed similar behavior under electric field, but the hard-doped material was more susceptible to mechanical load. A considerable fraction of the piezoelectric coefficient originated from poling by the preferred orientation of 180° domains.

Measurement of Flexoelectric Effect in Lead Zirconate Titanate Ceramics

Lead zirconate titanate (PZT) ceramics is usually used as a piezoelectric material. However it has characteristics of not only piezoelectricity but also flexoelectricity. Piezoelectricity is a phenomenon that electric polarization is induced by strain, and flexoelectricity is the one that the polarization is induced by strain gradient. In this study, flexoelectricity in poled soft PZT ceramics is measured. In order to eliminate influence of piezoelectricity, PZT ceramic thin plates are subjected pure bending using four-point bending experimental mechanism. Strain gradient along the direction of thickness in the plate is caused by the bending motion. Electric charge between two electrodes which is set on the center of the plate surface is measured under quasi-static sinusoidal load. Even though the polarization for piezoelectric effect is eliminated by the experimental setup, the influence of piezoelectric effect still remains since polarization by piezoelectricity is much larger than the one by flexoelectricity. So the influence of piezoelectricity is eliminated using qualitative difference between piezoelectricity and flexoelectricity for poling direction. Eventually, flexoelectric coefficient of the order of 10-5 C/m is measured.