TiO3 Piezoelectric Ceramics Research Articles

A-site and B-site cation doping engineering: A strategy to enhance strain in Pb(Zr, Ti)O3-based ceramics

Pb(Zr, Ti)O3 piezoelectric ceramics with high strain and low hysteresis are essential for ultra-precision driving and positioning in advanced manufacturing and control fields. In this study, the doping engineering via dual cations was utilized to improve the strain characteristics of Pb(Zr, Ti)O3-based ceramics, and thus the ceramics 0.3PbTiO3–0.65PbZrO3–0.05(Bi0.3La0.7)(Zn0.5Ti0.5)O3–x wt% (La2O3+Nb2O5) were probed. Results show that excellent comprehensive performance is fulfilled for the ceramic with x = 5, i.e., a high strain S = 0.45 %, low strain hysteresis Hy =16 %, and high piezoelectric coefficient d33 = 585 pC/N. For modified ceramics, the large electrostrictive strain stems from the synergistic role of lattice distortion and transformation of electric domain morphology due to cations doping. This study demonstrates a productive cation co-doping engineering to enhance the electrostrictive strain in Pb(Zr, Ti)O3-based ceramics, which enables the ceramics to have good features applied in piezoelectric actuators.

Effect of processing temperature on structural and electrical properties of lead-free K0.5Bi0.5TiO3 piezoelectric ceramics synthesized by sol-gel technique

Effect of processing temperature on structural and electrical properties of lead-free K0.5Bi0.5TiO3 piezoelectric ceramics synthesized by sol-gel technique

Ultrahigh strain in PZ-PT-BNT piezoelectric ceramic

Low strain limits the further application of Pb(Zr,Ti)O3 (PZT) piezoelectric ceramics in actuators. Herein, a ternary piezoelectric ceramic xPbTiO3-(0.95-x)PbZrO3-0.05(Bi0.5Na0.5)TiO3 (xPT-PZ-BNT) is proposed and prepared by solid-state method to improve the strain characteristics. Results indicate that a biased electric field is intentionally constructed by defects arising from the incorporation of BNT into PZ-PT ceramic, which promotes non-180° domains to restore to initial states, thereby contributing to the increase in strain. Moreover, the electric domain configuration is efficiently modified by adjusting the component proportion in xPT-PZ-BNT ceramics, in which the 0.42 PT-PZ-BNT presents short and broad domains with fast response to external electric field. Rayleigh analysis indicates that the strain contributed by domain switching is dominant in PT-PZ-BNT ceramics under a high electric field. Consequently, a large strain of 0.4% is achieved in 0.42 PT-PZ-BNT ceramic with the variation less than 10% in the temperature range of 25∼175 °C. This study not only deeply analyzes the effect of domain configuration on the strain for PZT piezoelectric ceramics, but also demonstrates an effective approach to increase the strain through constructing internal biased electric field and regulating domain configuration.

Comprehensive optimization of piezoelectric coefficient and depolarization temperature in Mn-doped Bi0.5Na0.5TiO3-Bi0.5K0.5TiO3-BaTiO3 lead-free piezoceramics

Lead-free Bi0.5Na0.5TiO3 (BNT) piezoelectric ceramics have the advantages of large coercive fields and high Curie temperatures. But the improvement of piezoelectric coefficient (d33) is usually accompanied by a huge sacrifice of depolarization temperature (Td). In this work, a well-balanced performance of d33 and Td is achieved in MnO2-doped 0.79(Bi0.5Na0.5TiO3)-0.14(Bi0.5K0.5TiO3)-0.07BaTiO3 ternary ceramics. The incorporation of 0.25 mol% MnO2 enhances the d33 by more than 40%, while Td remains almost unchanged (i.e., d33=181 pC/N, Td=184 °C). X-ray diffraction (XRD) shows that an appropriate fraction of the small axis-ratio ferroelectric phase (pseudo-cubic, Pc) coexists with the long-range ferroelectric phase (tetragonal, T) under this MnO2 doping. Piezoelectric force microscopy (PFM) has revealed a special domain configuration, namely large striped and layered macro domains embedded with small nanodomains. This study provides a distinctive avenue to design BNT-based piezoelectric ceramics with high piezoelectric performance and temperature stability.

Polarization response and thermally stimulated depolarization currents of the modified (Ba,Ca) (Zr,Ti)O3 piezoelectric ceramics

Polarization response and defect mechanism of the (Ba,Ca) (Zr,Ti)O3 piezoelectric ceramics by doping modification were intensively investigated. The Al-doping leads to the reduced piezoelectric polarization responses, but optimizes fatigue resistance and the quality factor, showing the acceptor characteristics. A way to test thermally stimulated depolarization currents (TSDC) is utilized to distinguish the role of defect dipole from oxygen vacancy and uncover the intrinsic reason of improving cyclic fatigue behavior. It has been confirmed that the improvement of fatigue behavior can be attributed to the formation of oxygen vacancies by Al doping. The present study gives a promising method to reveal the origin of piezoelectric characteristics based on defect configuration in advanced dielectrics.

The grain growth mechanisms for 0.8(Bi,Na)TiO3-0.2(Sr,Ti)O3 ceramics prepared using a two-step sintering process

ABSTRACT In this study, lead-free 0.8(Bi,Na)TiO3-0.2(Sr,Ti)O3 piezoelectric ceramics were prepared using a two-step sintering process to analyze their sintering mechanisms. Two-step sintering process has benefits of being able to be conducted at lower temperatures than conventional sintering process, but the complicated sintering mechanisms involved in this process have not been yet fully investigated. Therefore, in the present study, two-step sintering mechanism for lead-free piezoelectric ceramics was analyzed by estimating the activation energy required depending on the sintering conditions. Using the two-step sintering process, the piezoelectric charge and electromechanical coupling coefficients improved from 146 pC/N and 0.347 to 163 pC/N and 0.377, respectively. By comparing the grain-growth mechanisms for the conventional and two-step sintering processes, it appeared that the sintering mechanisms differed. By introducing the two-step sintering process, piezoelectric ceramics with improved piezoelectric charge and electromechanical coupling coefficients were produced.

Hardening of (Ba0.5Na0.5)0.85Ba0.15TiO3 lead-free piezoelectric ceramics by adding (Bi0.5Na0.5)MnO3

The hardening of (Bi0.5Na0.5)0.85Ba0.15TiO3 (BNBT15) piezoelectric ceramics was investigated by adding raw materials with Bi0.5Na0.5MnO3 (BNM). BNBT15-BNM exhibited a single phase of BNBT15. BNM acts as a sintering aid for BNBT15 to produce domain pinning, and produces tetragonality based on BaTiO3 for increased stability. BNBT15-BNM hardens piezoelectric material with low Mn content, increasing the coercive field and mechanical quality factor. The mechanical quality factor of BNBT15-BNM (0.75 wt%) exceeded 1200. In high-power conditions, BNBT15-BNM (0.75 wt%) exhibited a vibration velocity twice that of hard-PZT. The quality factor gradually decreased with a high vibration velocity. The equivalent stiffness slightly decreased with strain, and the mechanical nonlinearity was much less than that of hard-PZT. BNBT15-BNM (0.75 wt%) has superior high-power properties, and is expected to be a candidate material for use in lead-free piezoelectric ceramics in high-power applications.

Electrical Properties of Lead-Free (Bi0.5Na0.5)TiO3 Piezoelectric Ceramics Induced by BNT Nanoparticles

Electrical Properties of Lead-Free (Bi0.5Na0.5)TiO3 Piezoelectric Ceramics Induced by BNT Nanoparticles

Rapid preparation of Bi0.5Na0.5TiO3 ceramics by reactive flash sintering of Bi2O3-NaCO3-TiO2 mixed powders

Lead-free Bi0.5Na0.5TiO3 piezoelectric ceramics were successfully prepared by reactive flash sintering of Bi2O3-NaCO3-TiO2 mixed powders, where phase transformation and densification occurred simultaneously. The influence of electric field strength, current density and holding time at constant current state on the phase transformation and densification were investigated. The current density had a significant influence on the extent of phase transformation and densification. The holding time had no influence on the phase transformation, but had an important effect on crystallinity of sample. The sintered bulks exhibited the maximum polarization Pm of 16.8 μC/cm2, remanent polarization Pr of 9.6 μC/cm2, coercive field Ec of 29 kV/cmm, maximum electric-field-induced strain of 0.053 %, and piezoelectric coefficient d33 of 85 pC/N. The reactive flash sintering can prepare the dense and single-phase ceramics from multiphase precursor powders in one step of flash, providing a new way for rapid production of ceramic materials.

Enhanced electric field-induced strain and electrostrictive response of lead-free BaTiO3-modified Bi0.5(Na0.80K0.20)0.5TiO3 piezoelectric ceramics

ABSTRACT Lead-free (1-x)Bi0.5(Na0.80K0.20)0.5TiO3-xBaTiO3 or (1-x)BNKT-xBT (x = 0 – 0.15 mol fraction) piezoelectric ceramics have been investigated. The optimum density was found for the ceramic sintered at 1125°C, corresponding 98 – 99% of their theoretical values. All ceramics had a single perovskite structure. The coexisting mixed tetragonal-rhombohedral phases all over the entire compositional range with tetragonal phase becoming superior at higher BT. The diffuse phase transition was promoted by the addition of BT. With increasing BT content, the Tm and Td values were found to decrease. Phase transition from ferroelectric (FE) phase to ergodic relaxor (ER) phase was also induced by the changes in BT content. These changes significantly suspended long-range ferroelectric order, then correspondingly reducing the Pr and Ec , resulting in an improvement of electrostrictive and electric field-induced strain responses. A significant increasing of electric field-induced strain response (Smax = 0.37% and d*33 = 630 pm/V) is noted for the x = 0.05 ceramic. Furthermore, high electrostrictive coefficient (Q33 ) of 0.0421 m4/C2 is observed for this composition, which was more than ~ 2 times (~108%) as compared to the pure BNKT ceramic. The studied results indicated these ceramics can be considered promising candidates for actuator applications.

Structure evolution and electrical properties of lead-free Bi0.5Na0.41K0.09TiO3 piezoceramics by isovalent La doping

This study investigated the structure evolution, surface morphology, dielectric properties, ferroelectric properties, piezoelectric properties, and electromechanical strain properties of lead-free (Bi0.5−xLax)(Na0.41K0.09)TiO3 piezoelectric ceramics. All samples were fabricated by a traditional solid-state synthesis. The effects of La3+-isovalent substituted on Bi3+-site of the Bi0.5Na0.41K0.09TiO3 system were examined. The addition of La doping in the Bi0.5Na0.41K0.09TiO3 ceramics induced the second phase of K4Ti3O8 and a crystal structural change from the rhombohedral and tetragonal phase to a pseudocubic phase. All samples show similar grain morphology and dense microstructure with the average grain size around 1.33 to 1.61 μm. The dielectric curves and field-induced polarization loops of samples confirm the nonergodic-to-ergodic relaxor phase transformation, corresponding to the reduction of the temperature at the phase transition from ferroelectric to relaxor phase and the disruption of the ferroelectric properties happened in samples when increasing La3+ content. Besides, the maximum piezoelectric constant of 139 pC/N was found in (Bi0.48La0.02)(Na0.41K0.09)TiO3 ceramic, while the (Bi0.46La0.04)(Na0.41K0.09)TiO3 ceramic shows a maximum strain of ~ 0.2% at a low field of 40 kV/cm.

Influence of A-site non-stoichiometry on electromechanical properties of Sr(Hf0.5Zr0.5)O3-modified Bi0.5(Na0.8K0.2)0.5TiO3 piezoelectric ceramics

Effect of Na non-stoichiometry in Sr(Hf0.5Zr0.5)O3-modified Bi0.5(Na(0.8+x)K0.2)0.5TiO3 ceramics was examined in the range of − 0.04 ≤ x ≤ 0.04. The effect of Na non-stoichiometry on microstructure, ferroelectric, piezoelectric, dielectric properties and high-temperature impedance was explored. Compared to the stoichiometric compositions, Na excess and deficiency exhibit the same effect as observed for the acceptor and donor doping, respectively. All non-stoichiometric and stoichiometric compositions exhibit a pure ABO3 perovskite phase with pseudocubic symmetry. The deficiency of Na in ceramics decreases the grain size and drives the system towards ergodic relaxor as evident by pinched ferroelectric loop and the negligible negative strain along with an increase in maximum strain (Sm). The corresponding normalized strain (Sm/Emax.) increased from 275 to 800 pm/V when Na content decreased from x = + 0.04 to − 0.04. In contrast, excess Na exhibits the converse effect and drives the system towards ferroelectricity. Composition with deficient Na also exhibits lower dielectric loss and increase in resistivity by an order of magnitude compared to excess Na as observed from the high-temperature dielectric and impedance measurements. The results of this study demonstrate that Na non-stoichiometry significantly affects the electric properties of the studied system and thus can be effectively modulated to achieve improved electromechanical properties for materials having actuator-based applications.

Lead Free (Bi, Na)TiO3–BiAlO3 Ceramics for Piezoelectric Application

In this research, substitution effects of BiAlO3 with (Bi, Na)TiO3 piezoelectric ceramics was investigated for the sensors and actuators applications. (Bi,Na)TiO3 material has been employed for the piezoelectric devices applications because of their high piezoelectric charge constant, d33, of 88 pC/N, electromechanical coupling coefficient, kp, of 22% and inverse piezoelectric charge constant of 498 pm/V. As a piezoelectric material, (Bi, Na)TiO3 has perovskite structure with tetragonal basis. The improvement of piezoelectric and inverse piezoelectric properties is important for industrial device applications. Therefore, in this research, we have tried to increase functional and electrical properties of (Bi, Na)TiO3 piezoelectric materials by substituting BiAlO3 dopants. As a result, the piezoelectric constant was increased up to 140 pC/N, and the densification was increased up to 5.92 g/cm3 .

Electric field-induced strain in Sr(Hf0.5Zr0.5)O3-modified Bi0.5(Na0.8K0.2)0.5TiO3 piezoelectric ceramics

Lead-free Sr(Hf0.5Zr0.5)O3-modified Bi0.5(Na0.8K0.2)0.5TiO3 (SHZ-BNKT) ceramics were synthesized using a conventional solid-state, mixed-oxide method. In complex solid solutions such as BNKT, the role of a ternary additive is important because it can break up the long-range dipole order, which destabilizes the ferroelectric phase leading to relaxor behavior. In this system, as verified by x-ray diffraction, SHZ was incorporated into the BNKT perovskite lattice throughout the studied compositional range. The coexistence of tetragonal and rhombohedral phase was observed for x = 0.00 and with the addition of SHZ, a transition to pseudocubic symmetry was observed, which is indicative of the onset of relaxor behavior. To characterize the relaxor properties of the material, the polarization–electric field hysteresis, dielectric, and electric-field-induced strain behaviors were studied as a function of composition. The temperature-dependent dielectric spectra showed frequency dependence for all the SHZ-modified BNKT ceramics, which is a typical characteristic of relaxor ferroelectrics. Furthermore, constriction in polarization loops and an absence of negative strain in the bipolar strain measurement for SHZ-modified BNKT compositions confirms that the addition of SHZ significantly disrupts the ferroelectric order. The addition of 2 mol. % SHZ in BNKT markedly enhanced the electric field-induced strain from 0.10% (for pure BNKT) to 0.33% (for 2% SHZ-BNKT). The corresponding normalized strain coefficient (d33∗=Smax/Emax) increased from 196 pm/V to 663 pm/V at a moderate electric field of 50 kV/cm. These results indicate that BNKT–SHZ ceramics can be designed for an improved strain response via a cation substitution-induced relaxor state for electromechanical actuator applications.

BaTiO3 nanowires-induced phase transition and thermally stable strain in (Bi0.5Na0.5)TiO3 piezoelectric ceramics

Environment-friendly lead-free piezoceramics with high strain response and extremely excellent stability in a wide operating temperature range are critically important in practical actuator applications. Here, we develop a new strategy to tune the electrostrictive strain behavior in Bi 0.5 Na 0.5 TiO 3 (BNT)-based ceramics via using high aspect ratio BaTiO 3 nanowires (BT NWs) as a modifier. The addition of BT NWs generates a crossover from a typical ferroelectric (BT conventional spherical particles) to a complete ergodic relaxor (ER) phase at ambient temperature, accompanied by a large electrostrictive strain of ∼0.17% with d 33 *( S max / E max ) = 284 pm/V. Such a high electrostrictive strain is extremely thermally stable with only <7% fluctuation from 27 °C to 120 °C. In addition, the BT NWs-modified ceramics also exhibit acceptable fatigue endurance (<30% up to 10 5 cycles) and frequency dependence (<20% at 10Hz–100Hz). These achieved exceptional performances can be ascribed to the BT NWs-driven complete ER phase at room temperature. The findings of this study can inspire enhanced interest in nanowires as a viable modifier to BNT-based materials due to promising potential for practical actuator applications in a wide temperature range.

Impedance Matching Techniques of Multi-layered PZT Ceramics for Piezoelectric Energy Harvesters

In this research, the possibility of passive damping system based on the piezoelectric energy harvesting has been proposed and tested. To apply passive damper system, piezoelectric ceramics were stacked, and impedance was matched. Piezoelectric energy harvesters were employed due to their excellent piezoelectric and robust properties. Especially, multilayered (Pb,Zr)TiO3 piezoelectric ceramic have high piezoelectric charge coefficient d33 and piezoelectric voltage coefficient g33 for actuator and harvester applications, respectively. Multilayered (Pb,Zr)TiO3 piezoelectric ceramics can generate comparatively high current level compared with single layered piezoelectric ceramics due to its parallel connected capacitors. In energy harvester applications, multilayered (Pb,Zr)TiO3 piezoelectric ceramics have a role of voltage source with capacitive impedance. Due to considerable impedance in voltage sources, the role of impedance matching between the source and output terminal is more critical. By employing the piezoelectric energy harvesting system for the passive damper, output energy of 11 μJ/cm3 was obtained at the 100 μF capacitors. Therefore, impedance matching technologies were intensively investigated to obtain maximum output energy for storing capacitors.

Enhanced Ferroelectric and Converse Piezoelectric Properties of Dense Lead-Free Na&amp;lt;sub&amp;gt;0.4&amp;lt;/sub&amp;gt;K&amp;lt;sub&amp;gt;0.1&amp;lt;/sub&amp;gt;Bi&amp;lt;sub&amp;gt;0.5&amp;lt;/sub&amp;gt;TiO&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt; Ceramics for Actuator Applications

In this work, lead-free Na0.4Bi0.5 TiO3-K0.1Bi0.5TiO3 (NKBT) piezoelectric ceramics were prepared by the solid-state reaction method and their structural, ferroelectric and dielectric properties were systematically studied. NKBT sintered at 1150℃ for 4 h exhibited highly dense (96% - 98% of the theoretical density) and uniform grains of size 1.1 μm. The coexistence of tetragonal (P4bm) and rhombohedral (R3c) phases due to the presence of morphotrophic phase boundary for the chosen composition has been confirmed by the Rietveld refinement studies. Enhanced ferroelectric properties such as remnant polarization (Pr) and coercive field (EC) are found to be 37 μC/cm2 and 30 kV/cm, respectively. The optimized synthesis procedure for NKBT ceramics resulted in enhanced strain (%) and converse piezoelectric coefficient (d33*) of 0.3 % and 554 pm/V which is attributed to smaller grain size and switching of non 180o domains. NKBT ceramics with such excellent piezoelectric properties can be considered as a promising candidate for actuator applications.

Effects of Excess Barium on the Structure and Electrical Properties of (Ba,Ca)TiO3 Piezoelectric Ceramics with High Mechanical Quality Factors

Manganese-doped Ba0.925Ca0.075TiO3 lead-free piezoelectric ceramics (abbreviated as BCT) with high mechanical quality factor were synthesized by conventional solid-state reaction method. The effects of excess Ba on the crystal structure, microstructure, and electrical properties of the ceramics were systematically investigated. X-ray diffraction and Raman spectra revealed that Ca2+ ions were pushed from Ba sites to Ti sites of BCT when 1.5 mol% extra Ba2+ ions were added after sintering. The grain size of the ceramics was decreased by adding extra Ba2+ ions. The mechanical quality factor and resistivity of the ceramics decreased dramatically when the excess Ba was more than 1.5 mol%. High piezoelectric coefficients ( d33 = 150–190 pC/N ) and high mechanical quality factors ( Qm = 1 000–1 200 ) were obtained in the ceramics when the excess of Ba was between 0.5 mol% and 1 mol%. These results indicated that the properties of BCT ceramics could be tailored by adjusting the content of Ba.

Lead-free piezoelectrics—The environmental and regulatory issues

Abstract

High thermal stability of energy storage density and large strain improvement of lead-free Bi0.5(Na0.40K0.10)TiO3 piezoelectric ceramics doped with La and Zr

Properties of lead-free Bi0.5-xLaxNa0.40K0.10Ti0.98Zr0.02O3 (x = 0.000–0.040) ceramics were investigated. All ceramics have a pure perovskite structure. A high energy storage density (∼1.00 J/cm3) at room temperature (RT) is noted for the x = 0.030 sample, while x = 0.020 and 0.040 samples have very high thermal stability of energy storage density of ∼3% (at 75–150 °C). Furthermore, the x = 0.030 and 0.040 samples have the highest energy storage efficiency (η) value of 94% at 125 °C with high thermal stability (η = 84–95% at 25–150 °C). The x = 0.005 sample has high electric field-induced strain (Smax = 0.42%) and high normalized strain coefficient (d*33 = Smax/Emax = 700 pm/V) with large improvements (∼200% and 163% for Smax and d*33, respectively), as compared to the based composition. This ceramic system has potentials for piezoelectric and/or energy storage density applications.