High Field-induced Strain Research Articles

Origin of high comprehensive electromechanical properties of novel donor and acceptor–codoped PMN–30PT ceramics

Donor and acceptor–codoped PMN–30PT ceramics with 1–3 mol% Sm and 1 mol% Mn were fabricated via a two-step solid-state reaction. The crystal structure and electrical properties were investigated in detail. Donor Sm and acceptor Mn codoping substantially enhances the electromechanical, piezoelectric, and dielectric properties with a high piezoelectric coefficient d33 = 483–680 pC/N, a high mechanical quality factor Qm = 518–642, a high field-induced strain = 0.20%–0.24 %, and a low dielectric loss tan δ = 0.54%–0.69 %. X-ray diffraction and Raman spectra reveal the coexisting triple phase composition of the rhombohedral phase, tetragonal phase, and monoclinic polar nanoregions. Thermally stimulated depolarization current verifies the formation of various defect dipole clusters such as (MnTi″–VO··)×. With enhanced local structure heterogeneity induced by Sm, the phase composition and defect chemistry are regarded as the origin of such high comprehensive performance.

Pb(In1/2Nb1/2)O3-PbZrO3-PbTiO3 ternary ceramics with temperature-insensitive and superior piezoelectric property

The development of ferroelectric ceramics with both large piezoelectric responses and broad service temperature range is still a key challenge for practical applications due to the so-called d33-TC trade-off. Here we report the strategy to utilize the synergistic contribution of morphotropic phase boundary and enhanced local structural heterogeneity, in which an excellent piezoelectric coefficient d33 of 680 pC/N and a high Curie temperature of 330 ℃ are simultaneously achieved in Sm modified 0.25PIN-0.325PZ-0.425PT ceramics. The underlying mechanism responsible for the high dielectric and piezoelectric properties is studied based on cryogenic dielectric measurement and Rayleigh analysis. Of particular interest is that, a high field-induced strain of 0.19% is achieved in 0.25PIN-0.32PZ-0.43PT at electric field of 20 kV/cm, corresponding to a piezoelectric d33 * of 945 pm/V, showing an excellent temperature stability with minimal variation of 7% up to 310 °C. This work demonstrates the introduction of high temperature end members and rare earth doping are conducive to ferroelectric solid solutions with desired broad usage temperature range and superior piezoelectric properties, which will greatly benefit high temperature actuator applications.

Electromechanical properties in CaTiO3 modified Na0.5Bi0.5TiO3-BaTiO3 solid solutions above morphotropic phase boundary

The structural, electromechanical, and dielectric properties of (1 − x)(0.8Na0.5Bi0.5TiO3-0.2BaTiO3)-xCaTiO3 [(1 − x) (0.8NBT-0.2BT)-xCT] ceramics are studied as candidates for room temperature actuators with high field-induced strain. The choice of 0.8NBT-0.2BT as a starting composition is motivated by the large tetragonality in this concentration range, even though it is located far away from the morphotropic phase boundary. CaTiO3 was chosen as a third component to decrease the depolarization temperature and achieve a high field-induced strain at room temperature. The measured strains at the field-induced phase transition are remarkably lower than might be expected from the jump in unit cell parameters at the phase transition. This inconsistency could be related to an incomplete field-induced phase transition from the ferroelectric phase to the nonpolar phase. Among all of the manufactured samples, the phase transition is close to room temperature in the composition with x = 0.100, which allows obtaining unipolar strains up to 0.23% at E = 65 kV/cm. Electrostrictive-like strain was observed not only above the depolarization temperature but also in the region of field-induced phase transition.

Enhanced piezoelectricity in (K, Na)NbO3-based ceramics by optimizing composition and texture process

In this study, <00l>-textured (1-x)(K0.5Na0.5)0.95Li0.05Nb0.93Sb0.07O3-xBaZrO3 [abbreviated as (1-x)KNLNS-xBZ, x = 0.01, 0.02, 0.04, 0.06, 0.08] lead-free ceramics are prepared by template grain growth (TGG) method using NaNbO3 templates. The effects of BZ content on the phase structure, microstructure, as well as electrical properties of ceramics are investigated. Large piezoelectric constant d33 (∼234 pC/N) and planar electromechanical coupling factor kp (∼38.42%) are obtained in the ceramics with x = 0.02, and high field-induced strain (d33∗ ∼ 403.5 pm/V) is also achieved in the rhombohedral-orthorhombic-tetragonal phase coexistent area due to multiphase coexistence. These results show that the introduction of BaZrO3 is a very effective way to improve the electrical properties of textured (K0.5Na0.5)0.95Li0.05Nb0.93Sb0.07O3 lead-free piezoelectric ceramics.

Plano-convex Variable Focal Length Micro-lens with a Polymer Nanocomposite Actuator

An electromechanical actuator based on a P(VDF-TrFE-CFE) / BaTiO3 terpolymer nanocomposite of high field-induced strain was used in a variable focal length micro-lens design. The liquid-filled micro-lens consisted of a fluidic chamber, structured on a silicon wafer and sealed by an elastomeric lens membrane with a round-shaped nanocomposite actuator attached to it. A fabrication process was developed taking into account also particular characteristics of the actuator material for thin film parameter optimization. A change in the focal length of the fabricated micro-lens with a nanocomposite actuator was successfully demonstrated. Specifically, a 3 mm aperture, plano-convex variable focal length micro-lens of optical power ranging from 21 dpt to 13 dpt was obtained by varying the electric field applied on the nanocomposite actuator.

Multilayer piezoelectric haptic actuator with CuO-modified PZT-PZNN ceramics

A piezoelectric haptic actuator composed of a multilayered ceramic (MLC) of 0.5mol% CuO-modified 0.69Pb(Zr0.47Ti0.53)O3–0.31[Pb(Zn0.4Ni0.6)1/3Nb2/3]O3 (0.5CPZT-PZNN) ceramic was developed and characterized. The 0.5CPZT-PZNN ceramic was well-sintered at 900°C. This ceramic showed a small εT33/εo of 1801 and a large d33 of 570 pC/N, necessary characteristics for high-performance actuators operating at low voltages. This ceramic also showed a high field-induced strain, maintained after 106 fatigue cycles. A three-layer MLC was synthesized at 900°C using this ceramic. Ag metal was used as the electrode for the MLC actuator. No inter diffusion between the Ag electrode and the 0.5CPZT-PZNN ceramic layer was observed. The MLC actuator exhibited a high free stroke of ±300μm even after 106 bending cycles. The piezoelectric haptic actuator fabricated using this MLC showed a large vibration acceleration of 2.1G with a low capacitance of 20nF. This demonstrates the suitability of the 0.5CPZT-PZNN ceramic for applications in piezoelectric haptic actuator.

Chemical and structural effects on the high-temperature mechanical behavior of (1−x)(Na1/2Bi1/2)TiO3-xBaTiO3 ceramics

Bismuth sodium titanate–barium titanate [(1−x)(Na1/2Bi1/2)TiO3-xBaTiO3, NBT-100xBT] is one of the most well studied lead-free piezoelectric materials due in large part to the high field-induced strain attainable in compositions near the morphotropic phase boundary (x = 0.06). The BaTiO3-rich side of the phase diagram, however, has not yet been as comprehensively studied, although it might be important for piezoelectric and positive temperature coefficient ceramic applications. In this work, we present a thorough study of BaTiO3-rich NBT-100xBT by ferroelastic measurements, dielectric permittivity, X-ray diffraction, and Raman spectroscopy. We show that the high-temperature mechanical behavior, i.e., above the Curie temperature, TC, is influenced by local disorder, which appears also in pure BT. On the other hand, in NBT-100xBT (x &amp;lt; 1.0), lattice distortion, i.e., tetragonality, increases, and this impacts both the mechanical and dielectric properties. This increase in lattice distortion upon chemical substitution is counterintuitive by merely reasoning on the ionic size, and is due to the change in the A-O bond character induced by the Bi3+ electron lone pair, as indicated by Raman spectroscopy.

Influence of zirconium substitution on dielectric, ferroelectric and field-induced strain behaviors of lead-free 0.99[Bi1/2(Na0.82K0.18)1/2(Ti1−x Zr x )O3]-0.01LiSbO3 ceramics

The Crystal structure, dielectric, ferroelectric and field-induced strain behaviors of lead-free 0.99[Bi1/2(Na0.82K0.18)1/2(Ti1−xZrx)O3]-0.01LiSbO3 (BNKTZ-LS) ceramics were investigated in the composition range x = 0 − 0.040. XRD patterns revealed the formation of a pure perovskite phase with no apparent structural phase transition. The temperature-dependent dielectric peaks of the BNKTZ-LS ceramics broadened and the ferroelectric polarizations decreased with increasing Zr concentration. Ferroelectric and bipolar field induced-strain curves indicated a disruption of ferroelectric order upon Zr addition into the BNKT-LS ceramics. This destabilization of the ferroelectric order was accompanied by an enhanced field-induced strain. A high field-induced strain (S = 0.30%) with a normalized strain (d*33 = Smax/Emax = 500 pm/V) was observed at an applied electric field of 6 kV/mm at x = 0.020.

Electromechanical properties of Ba(Zr 0.2Ti 0.8)O 3 ceramics prepared by spark plasma sintering

Ba(Zr 0.2Ti 0.8)O 3 (BZT20) ceramics were prepared by spark plasma sintering (SPS) and conventional sintering. The dynamic field-induced displacement and small-signal remnant piezoelectric constant measured by a resonant–antiresonant frequency method were evaluated. By normal sintering, the density, grain size, and dielectric constant of the ceramics increased with sintering temperature. The BZT20 ceramics prepared by SPS were characterized by linear field-induced strain. In response to the application of post-annealing at 1300 °C, BZT20 ceramics exhibited linear strain loop and high field-induced strain corresponding to dynamic strain/field d 33 at 20 kV/cm of 290 pm/V. The remnant piezoelectric properties of the BZT20 ceramics were found to largely depend on the preparation conditions, including the sintering temperature and annealing temperature. The BZT20 ceramics prepared by SPS and post-annealed at 1300 °C showed Q m and k p values of 325 and 25.1 (%), respectively.

Dynamic In Situ X-Ray Diffraction Study of Antiferroelectric–Ferroelectric Phase Transition in Strontium-Modified Lead Zirconate Titanate Ceramics

The electric field-induced electromechanical properties of strontium-modified lead zirconate titanate (PSZT) ceramics, at the Zr-rich region of the phase diagram, are investigated by a dynamic in situ x-ray diffraction technique. PSZT compositions with different Zr/Ti ratios are prepared using a tape lamination approach. An experimental setup using Bragg-Brentano parafocusing geometry is used for the in situ x-ray diffraction on samples under a dynamic ac electric field up to their saturation polarization at 0.1 mHz frequency. The results indicated that strains for the compositions in the ferroelectric rhombohedral (FR) phase field are mostly due to structural changes and non-180° domain movements after coercive field. As a result the experimental longitudinal strains in these materials are not very high (∼0.4%). On the other hand, for the compositions at the FR-AFT phase field, near the morphotropic phase boundary, dynamic in situ x-ray diffraction showed the continuous field-induced phase transition from the AFT → FR. It is also seen from the changes in the pseudo-cubic (111) diffraction peak that this phase transition is accompanied by movements of non-180o or 90o domains. This resulted in very high field-induced strain of ∼0.8% in these materials. The compositions farther away from the boundary in the AT side showed neither structural changes nor domain movements up to 9 KV/mm. This is commensurate with the low observed strain of 0.03% for these materials.

The Effect of Sintering Temperature on Lead-Free Bi0.5(Na0.78K0.22)0.5TiO3-(Na0.5K0.5)NbO3 Ceramics

Lead-free piezoelectric Bi0.5(Na0.78K0.22)0.5TiO3–(Na0.5K0.5)NbO3 ceramics have been synthesized by a conventional solid-state reaction methods at different sintering temperatures (1100–1200°C). The effect of sintering temperature on the crystal structure, density and electrical properties was investigated. The Bi0.5(Na0.78K0.22)0.5TiO3–(Na0.5K0.5)NbO3 ceramics sintered at an optimum temperature of 1150°C exhibited high density and electrical properties. High field-induced strain (0.22%) and high dynamic piezoelectric coefficient (S max/E max = d*33 = 440 pm/V) were obtained for samples sintered at 1150°C. These results are believed to be due to the high density and lower conductivities at this temperature.

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

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