High-power Piezoelectric Applications Research Articles

Simultaneous enhancement of piezoelectricity and mechanical quality factor in relaxor-ferroelectric crystals via defect engineering

Both high piezoelectric response and mechanical quality factors (Qm) are essential for high-power applications of ferroelectric materials. However, there always exists a trade-off between these two parameters, which makes the collaborative optimization to be a great challenge. Here, a hardening effect is achieved via defect engineering in the acceptor-doped PbTiO3-relaxor-ferroelectric crystals by alternating current poling technique. It is found that under the AC electric field, the defect diploes are decoupled into isolated charged defects and accumulate at domain walls, which strongly pin domain wall motions while promoting ferroelectric dipole dynamics. Consequently, simultaneous enhancement of d33 and Qm is realized, where d33 increases by 16% and Qm enhances by 51%. This work offers an efficient and convenient approach in material design for practical high-power piezoelectric applications.

Sodium lithium niobate lead-free piezoceramics for high-power applications: Fundamental, progress, and perspective

With the capability of interconversion between electrical and mechanical energy, piezoelectric materials have been revolutionized by the implementation of perovskite-piezoelectric-ceramic-based studies over 70 years. In particular, the market of piezoelectric ceramics has been dominated by lead zirconate titanate for decades. Nowadays, the research on piezoelectric ceramics is largely driven by cutting-edge technological demand as well as the consideration of a sustainable society. Hence, environmental-friendly lead-free piezoelectric materials have emerged to replace lead-based Pb(Zr,Ti)O₃ (PZT) compositions. Owing to the inherent high mechanical quality factor (<i>Q</i>_m) and low energy loss, (Li,Na)NbO₃ (LNN) materials have recently drawn increasing attention and brought advantages to high-power piezoelectric applications. Although the crystallographic structures of LNN materials were intensively investigated for decades, the technical strategies for electrical performance are still limited. As a result, the property enhancement appears to have approached a plateau. This review traces the progress in the development of LNN materials, starting from the polymorphism in terms of the crystal structures, phase transitions, and local structural distortions. Then, the key milestone works on the functional tunability of LNN are reviewed with emphasis on involved engineering approaches. The exceptional performance at a large vibration velocity makes LNN ceramics promising for high-power applications, such as ultrasonic welding (UW) and ultrasonic osteotomes (UOs). The remaining challenges and some strategic insights for synergistically engineering the functional performance of LNN piezoceramics are also suggested.

Coherent Precipitates with Strong Domain Wall Pinning in Alkaline Niobate Ferroelectrics.

High-power piezoelectric applications are predicted to share approximately one-third of the lead-free piezoelectric ceramic market in 2024 with alkaline niobates as the primary competitor. To suppress self-heating in high-power devices due to mechanical loss when driven by large electric fields, piezoelectric hardening to restrict domain wall motion is required. In the present work, highly effective piezoelectric hardening via coherent plate-like precipitates in a model system of the (Li,Na)NbO3 (LNN) solid solution delivers a reduction in losses, quantified as an electromechanical quality factor, by a factor of ten. Various thermal aging schemes are demonstrated to control the average size, number density, and location of the precipitates. The established properties are correlated with a detailed determination of short- and long-range atomic structure by X-ray diffraction and pair distribution function analysis, respectively, as well as microstructure determined by transmission electron microscopy. The impact of microstructure with precipitates on both small- and large-field properties is also established. These results pave the way to implement precipitate hardening in piezoelectric materials, analogous to precipitate hardening in metals, broadening their use cases in applications.

Characterization of Mn-Doped PIN-PMN-PT Single Crystal Grown by Continuous-Feeding Bridgman Method

Mn-doped Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (Mn:PIN-PMN-PT) single crystals are attractive piezoelectric materials owing to their high mechanical quality factor. However, the single crystal boules grown by the conventional Bridgman method show compositional variation along the growth direction. In particular, the Mn content exhibits large variation due to its severe segregation. To improve the compositional uniformity, we applied the continuous-feeding Bridgman method to the growth of a Mn:PIN-PMN-PT single crystal boule. Then, the composition and property distributions of the boule along the growth direction were evaluated. The results showed that excellent composition and property uniformity were carried out over 80mm in boule length. The ranges of the electromechanical coupling coefficient (k33) and the piezoelectric coefficient (d33) were 0.931–0.934 and 1352–1517 pC/N, respectively. The ranges of the mechanical quality factor (Qm31) and the depolarization field (Ed) were 417–535 and 785–859 V/mm, respectively. The Qm31 and the Ed values were higher than those of the non-doped PIN-PMN-PT single crystals. The continuous-feeding Bridgman method is therefore an effective technique for improving the uniformity of the Mn content. As a result, the Mn:PIN-PMN-PT single crystal grown by the continuous-feeding Bridgman method possesses excellent property uniformity with characteristics suitable for high power piezoelectric applications.

High-power piezoelectric properties of quenched (Bi0.5Na0.5)TiO3-based solid-solution ceramics

Lead-free piezoelectric ceramics based on 0.90(Bi0.5Na0.5)TiO3 – 0.04(Bi0.5Li0.5)TiO3 – 0.06BaTiO3 with additives MnCO3 (0.1 wt%) [BNLBT4-6 + Mn0.1], which have a morphotropic phase boundary composition, were prepared by controlling the quenching rate (QR) and, their high-power piezoelectric and electrical properties were examined. The depolarization temperature Td could be increased by controlling the QR. The Td with QR = 15.0 and 0.05 °C/s was 166 and 119 °C, respectively. Thus, Td was increased by about ∼40 °C due to the quenching effect. Moreover, vibration velocities (v0−p) were observed at 1.3 m/s even after quenching. Additionally, the values of d31, ɛ33T/ɛ0, and s11E decreased, whereas Qm increased after quenching. The quenching effect promoted the dielectric and elastic hardening of BNLBT4-6 + Mn0.1 ceramics. After quenching, Td increased, and the value of d31 × Qm maintained the same value as for ordinary firing (OF) with QR = 0.05. Consequently, quenching was found to be effective for increasing the Td and Qm, hence, a promising effect for high-power piezoelectric applications.

Hardening effect in lead-free piezoelectric ceramics

Ecologically sustainable development of piezoelectric ceramics has been the primary target of the community over the past 20 years. While the development of “soft” lead-free piezoelectric ceramics has been of high maturity, the understanding of “hard” lead-free piezoelectric ceramics is still far from satisfactory, leading to a limited chance for high-power applications. The review starts with an introduction of loss mechanisms and the hardening effect in piezoelectric ceramics, including three different models mainly developed based on the lead zirconate titanate system. Then, studies on the hardening behavior of BaTiO3-based, (Bi0.5Na0.5)TiO3-based, and (K0.5Na0.5)NbO3-based lead-free piezoelectric ceramics are summarized with emphasis on the approaches to enhance mechanical quality factor. Meanwhile, three different characterization methods of high-power performances are introduced: the constant-voltage method, constant-current method, and transient (or burst) method. Finally, the state-of-the-art lead-free ultrasonic transducer applications are highlighted. This paper concludes with the remaining challenges for the development of “hard” lead-free piezoelectric ceramics for high-power piezoelectric applications.

Design and development of high-power piezoelectric ceramics through integration of crystallographic texturing and acceptor-doping

This study demonstrates the integrated approach based upon texturing and acceptor doping for realizing a high-power piezoelectric ceramic with combined soft and hard properties. The textured Mn-doped 0.24 Pb(In1/2Nb1/2)O3-0.42 Pb(Mg1/3Nb2/3)O3-0.34 PbTiO3 (PIN-PMN-PT) ceramic exhibits enhanced piezoelectric coefficient d33 and electromechanical coupling factor k31 in comparison with random counterpart. This enhanced piezoelectric response originates from the combined intrinsic high piezoelectric properties of <001>-oriented grains, and reduced energy barrier for polarization rotation in textured ceramics. The BaTiO3 (BT) template in textured ceramics increases the tetragonality degree which results in improved coercive field Ec but decreased mechanical quality factor Qm in comparison with random counterpart. The decreased Qm values of textured ceramics are related to the crystallographic dependence of Qm and the enhanced domain mobility due to the existence of small size domains. The textured ceramic with 2 vol.% BT content exhibited an excellent combination of soft and hard piezoelectric properties, measured to be: d33 = 517 pC/N, Qm = 1147, Ec = 10.0 kV/cm, and tan δ = 0.49%, which is highly promising for high power piezoelectric applications.

Structure and electrical properties in Sb-doped Ba0.93Ca0.07Ti0.92Sn0.08O3 ceramics near the phase coexistence point

In this work, Sb-doped Ba0.93Ca0.07Ti0.92Sn0.08O3 ceramics were successfully prepared by conventional solid-phase sintering reaction process and their phase structure, microstructure, and electrical properties were investigated systematically. The enhanced piezoelectric and dielectric properties (d33 = 520 pC/N, kp = 0.475, Qm = 149.3, er = 6113 and tanδ = 1.73%) were obtained due to the co-existence of rhombohedral, orthorhombic and tetragonal phases near the room temperature. Meanwhile, the optimal ferroelectric properties (Pr = 8.17 μC/cm2, Ec = 1.56 kV/cm) were also gained at x = 0.15 mol%. The temperature dependence of dielectric constant reveals relaxation behavior at various frequencies, and relevant diffuse phase transition has been carefully studied. The large d33, er, low tanδ and the relaxation behavior in (1−x)Ba0.93Ca0.07Ti0.92Sn0.08O3–xSb2O3 (x = 0.15 mol%) ceramic make it as a potential candidate for high power piezoelectric applications and ceramic capacitors.

Effects of K4CuNb8O23 and GeO2 addition on microstructure and piezoelectric properties in KNbO3 ceramics

A combined additives study of lead-free KNbO3 (KN) ceramics in the solid-state reaction was performed to improve the mechanical quality factor (Qm) for high power piezoelectric applications. Improved Qm values of 1137 and 1241 were confirmed in KN specimens with addition of 1.0 mol% K4CuNb8O23 (KCN) and 1.0 mol% KCN + 0.5 wt% GeO2, respectively. It is important for achievement of the higher Qm in KN systems to control the composition of the Cu segregated phase. In this study, the Cu segregated phase which was necessary to improve the Qm resulted from decomposition of the KCN compound during the sintering. Co-doping of KCN and GeO2 to KN specimens has a remarkable effect in suppressing the deliquescence accompanying KCN addition and improvement of the Qm without significant deterioration of the electromechanical coupling factor k31.

Conductive mechanism and the enhancement high-power electrical properties of Mn-modified Bi(Sc3/4In1/4)O3–PbTiO3–Pb(Mg1/3Nb2/3)O3 high temperature piezoelectric ceramics

In this research, we report the improved high-power electrical properties and the conductive mechanism of the 0.40Bi(Sc3/4In1/4)O3–0.58PbTiO3–0.02Pb(Mg1/3Nb2/3)O3–xMnO2 (BSI–PT–PMN–xMn, x = 0.0–0.8) system synthesized by a modified two-step solid state reaction method. A pure perovskite phase has been detected by the X-ray diffraction analysis of the BSI–PT–PMN–xMn ceramics, and the mechanical quality factor Qm has been found to increase from 28 to 210 with Mn content increasing from 0.0 to 0.8. The DC resistivity measurement indicated that the resistivity of the BSI–PT–PMN–xMn ceramics increases firstly, reaching the maximum at x = 0.4, and then decreases with more Mn modified. The conduction behavior can be described by the intrinsic charge carriers conduction mechanism and extrinsic semiconductor conductive mechanism in different temperature range. The high DC resistivity over 109 Ω cm at 300 °C together with the good electrical properties of piezoelectric constant d33 336 pC/N, planar electromechanical coupling factor kp 42.8%, mechanical quality factor Qm 120 and Curie temperature Tc 414 °C of the BSI–PT–PMN–0.4Mn ceramics makes it promising candidates for high temperature high-power piezoelectric applications.

Material and device design for the high performance low temperature co-fired multilayer piezoelectric transformer

PZT-based perovskite structure relaxors are very attractive for high power piezoelectric applications. Targeting multilayer co-fired piezoelectric transformers, we developed a PNN-PMW-PZT system [Pb(Ni1/3Nb2/3)O3-Pb(Mg1/2W1/2)O3-0.9Pb(Zr0.5Ti0.5)O3+xMnO2] and used flux materials to decrease the sintering temperature. Systematically investigating the effect of MnO2 content on piezoelectric and dielectric properties, the composition with 0.25 wt% MnO2 hardener exhibited excellent piezoelectric properties after sintering at 1000 °C for 2 h (Qm: 1150, kp: 0.63, d33: 345, tan δ: 0.0040, εT33/ε0: 1030). In addition to the compositional development, this work also involved functional tests and high-power characterization of a multilayer piezoelectric transformer utilizing this new ternary system that provided 38 W/cm3 output power density with 92% efficiency and a step-up ratio of 7.

Dielectric, ferroelectric and piezoelectric properties of MnO2-doped Pb(Yb1/2Nb1/2)O3-Pb(Zr,Ti)O3 ceramics

0–0.8 wt% MnO2 doped 0.33Pb(Yb1/2Nb1/2)O3–0.18PbZrO3–0.49PbTiO3 (PYN-PZT) ceramics were prepared by solid state reaction method and the influence of MnO2 modification on their crystal structure, ferroelectric and piezoelectric properties of PYN-PZT ceramics was investigated. It was found that small amount of MnO2 modification did not change the crystal structure of the PYN-PZT ceramics. Whereas a large internal bias was observed which indicates the existence of defect dipoles. Piezoelectric constant (d33) decreased while mechanical quality factor (Qm) increased with the increase of MnO2 content due to the domain wall pinning effect. The influence of sintering atmosphere on the properties of Mn doped PYN-PZT ceramics was also investigated. For their high Curie temperature Tc, good piezoelectric properties and high Qm，MnO2 doped PYN-PZT ceramics may be suggested as good candidates for high power piezoelectric applications.

Impacts of acceptor doping on the piezoelectric properties and domain structure in NBT-based lead-free ceramics

The domain structure and piezoelectric properties of Mn-doped 0.79(Na0.5Bi0.5)TiO3-0.14(K0.5Na0.5)TiO3-0.07BaTiO3 (BNBK79) ceramics were studied. The relationship between macroscopic properties and microstructure was established. The pure and Mn doped BNBK79 ceramics show different dynamic behavior in strain behavior and polarization hysteresis, due to the different domain structure and domain switching behavior. The BNBK79 ceramics show dominating irregular watermarks domain configuration before poling, changes to simple parallel stripes after poling, while BNBK79-Mn ceramics show more complicated domain configurations, where regular domain stripes containing Herringbones assembled with watermarks are dominated before poling, and the Herringbones remain after poling. The pinning effect induced by MnTi''−V0.. defect dipoles accounts for the complicated domain structure and hinders the domain switching, resulting in “hard” properties (low dielectric loss of 0.6% and high mechanical quality factor Qm of 1100), makes BNBK79-Mn ceramics promising for high-power piezoelectric applications.

Investigation of MnO2‐doped (Ba, Ca)TiO3 lead‐free ceramics for high power piezoelectric applications

Abstractx% mol MnO2‐doped Ba0.925Ca0.075TiO3 ceramics (abbreviated as BCT‐Mnx, x=0‐1.5) were synthesized by conventional solid‐state reaction method. The effects of MnO2 addition and (Ba+Ca)/Ti mole ratio (A/B ratio) on the microstructure and electrical properties of the ceramics were investigated. The internal bias filed Ei was determined from the asymmetrical polarization hysteresis loops and found to increase with the doping concentration of MnO2. High mechanical quality factors (Qm&gt;1200) and low dielectric loss (tanδ&lt;0.5%) were found in the BCT‐Mn0.75 and BCT‐Mn1.0 ceramics with Ei&gt;3 kV/cm, meanwhile, the piezoelectric and electromechanical properties were found to decrease compared with the pure BCT, exhibiting a typical characteristic of “hard” behavior. Of particular interest is that the microstructure of BCT‐Mn0.75 ceramics could be controlled by changing the A/B ratio, where enhanced piezoelectric coefficient d33 on the order of 190 pC/N was obtained in the BCT‐Mn0.75 ceramics with A/B=1.01 due to its fine‐grained microstructure, with yet high Qm, being on the order of 1000. The high d33 and Qm in MnO2‐doped BCT ceramics make it a promising candidate for high power piezoelectric applications.

Characterization of acceptor-doped (Ba, Ca)TiO3 “hard” piezoelectric ceramics for high-power applications

Acceptor Mn or Co-doped Ba0.925Ca0.075TiO3 (abbreviated as BCT-Mn and BCT-Co) lead-free piezoelectric ceramics with high density and fine grains were synthesized by conventional solid-state reaction method. The phase structure and electrical properties of the ceramics were investigated. The acceptor-doped BCT ceramics were found to exhibit asymmetrical polarization-electric field hysteresis loops corresponding to the presence of an internal bias field Ei, indicating that the domain walls were pinned by preferentially oriented defect dipoles formed by the acceptors and oxygen vacancies. High mechanical quality factor Qm and low dielectric loss tanδ were obtained for the ceramics due to the strong internal bias field (Ei =4–5kV/cm). In particular, BCT-Mn ceramics exhibited the best properties, with mechanical quality factor Qm =1020, dielectric loss tanδ=0.2% and piezoelectric coefficient d33 =190 pC/N. Furthermore, the planar electromechanical coupling factor kp for BCT-Mn ceramics was found to be larger than 0.4 in the temperature range of 25°C to 75°C. These results indicate that the Mn-doped BCT lead-free ceramics material is a promising candidate for high-power piezoelectric applications.

Piezoelectric properties of high-temperature-poled Pb(Mn1/3Nb2/3)O3-PbZrO3-PbTiO3 solid solutions

The piezoelectric properties of high-temperature-poled high-density solid solutions with compositions of xPb(Mn1/3Nb2/3)O3-yPbZrO3-zPbTiO3 (xPMnN-yPZ-zPT; PMnNZT) with x = 0.020–0.180, y = 0.420–0.580, and z = 0.400–0.560 were investigated by using the resonant-antiresonant frequency method. The two optimal compositions that exhibited large values of d 33 · Q m (p), where d 33 is the piezoelectric coefficient (longitudinal length mode) and Q m (p) is the mechanical quality factor (radial mode) for high-power piezoelectric applications were x = 0.040, y = 0.540, and z = 0.420 in the rhombohedral and the morphotropic phase boundary (MPB) regions and x = 0.095, y = 0.435, and z = 0.470 in the MPB and the tetragonal regions. By comparing the maxima in d 33 · Q m (p) for high-temperature (HT)-poled PMnNZT samples with the maxima in d 33 · Q m (p) for room-temperature (RT)-poled PMnNZT samples that had been previously reported, the ratio of d 33 · Q m (p) HT /d 33 · Q m (p) RT was approximately 1.8, exhibiting a significant improvement due to HT-poling treatments.

Fabrication and characterization of binary piezoelectric (Bi1/2Na1/2)TiO3-Ba(Mn1/3Nb2/3)O3 solid solutions

High-density solid solutions with compositions of (1−x)(Bi1/2Na1/2)TiO3−xBa(Mn1/3Nb2/3)O3 (BNT-BMN), with x = 0 − 0.06, were prepared by using the conventional ceramic fabrication process. The optimal composition that yielded the best piezoelectric properties for high-power piezoelectric applications was investigated. X-ray diffraction (XRD) analyses of BNT-BMN with x = 0 − 0.06 suggested that the rhombohedral-pseudocubic morphotropic phase boundary (MPB) for this material system is in the compositional region 0.035 ≤ x ≤ 0.04 at room temperature. A hard-mode BNT-BMN with x = 0.03, which lay on the rhombohedral side near the MPB region, exhibited excellent piezo- and ferroelectric properties.

High-power piezoelectric characteristics of manganese-modified BiScO3–PbTiO3 high-temperature piezoelectric ceramics

Hard piezoelectric ceramics of manganese (Mn)-modified 0.36BiScO3–0.64PbTiO3 (0.36BS–0.64PTM) with a high Curie temperature were prepared using the traditional solid-state reaction method. The effects of different concentrations of Mn on the structure, dielectric and piezoelectric properties of the 0.36BS–0.64PTM ceramics were investigated. X-ray diffraction results indicated that the 0.36BS–0.64PTM ceramics showed a single perovskite structure with tetragonal symmetry and the c/a ratio decreased slightly with increasing Mn content. The grain sizes of the 0.36BS–0.64PTM ceramics were enlarged by Mn addition, and their distributions were uniform. The dielectric loss tan δ decreased clearly with the increase in Mn content, and the mechanical quality factor Qm and vibration velocity v0 were improved significantly at the same time. The Curie temperature Tc, the planar electromechanical coupling factor kp, dielectric loss tan δ, mechanical quality factor Qm and vibration velocity v0 of the 0.36BS–0.64PTM ceramics with 3 mol% Mn were about 431 °C, 0.57, 0.007, 134 and 1.05 m s−1, respectively. The maximum vibration velocity v0 of the 0.36BS–0.64PTM ceramics is much superior to those of PZT (0.4 m s−1) ceramics and PZT–PZM (0.72 m s−1). These results indicated that the 0.36BS–0.64PTM ceramics are promising candidates for high-temperature and high-power piezoelectric applications.

High-Power Piezoelectric Characteristics of C-Axis Crystal-Oriented (Sr,Ca)2NaNb5O15 Ceramics

The high-power piezoelectric characteristics of c-axis crystal-oriented (Sr,Ca)2NaNb5O15 (SCNN) ceramics were studied by the constant-motional-current driving method, and compared with those of the randomly oriented ceramics superior to those of hard Pb(Ti,Zr)O3 (PZT) ceramics. The c-axis crystal-oriented SCNN ceramic showed a large Lotgering factor of 0.98. The effective piezoelectric constant d33* was 260 pm/V, as large as those of hard PZT ceramics. In the 31-mode of the rectangular plate, the quality factor, Q, was five times larger than that of the randomly oriented ceramic, and almost constant at approximately 3300 up to the maximum vibration velocity of 1.84 m/s rms. The resonant frequency change was also stable up to a vibration velocity of 1.84 m/s rms. The change was approximately +0.05% in the driving range, which was much smaller than that of +0.8% of the randomly oriented ceramic. The high-power piezoelectric characteristics were also clarified by a comparison with the mechanical characteristics. Therefore, the highly c-axis crystal-oriented SCNN ceramics are good candidates for high-power piezoelectric applications in comparison with hard PZT ceramics.

ハイパワー圧電応用を目指したPb(Mn1/3Nb2/3)O3-PbTiO3-PbZrO3系圧電材料の探索

ハイパワー圧電応用を目指したPb(Mn1/3Nb2/3)O3-PbTiO3-PbZrO3系圧電材料の探索