Introduction

Piezoelectric ceramics efficiently convert electrical energy to mechanical energy and vice versa, making them essential in various electromechanical applications, such as ultrasonic sensors1, transducers2, piezoelectric actuators3,4 and mechanical energy harvesting, among others. As market demands for high energy density and ease of miniaturization increase, selecting a piezoelectric material with optimized properties becomes crucial. Currently, lead-containing piezoelectric materials hold a major share in the market due to their overall superior piezoelectric properties. However, given the environmental concerns and health risks associated with lead-based materials and the growing emphasis on green and sustainable development, the need to develop high performance lead-free piezoelectric ceramics is becoming increasingly urgent.

Over the past two decades, extensive research has focused on various lead-free piezoelectric ceramics, such as: BaTiO35,6, (1-x)Bi0.5(Na,K)0.5TiO3-xBaTiO37,8, (K1-xNax)NbO3 (KNN)9,10 and BiFeO3-BaTiO3 (BF-BT)11,12. Among these materials, KNN system has attracted considerable attention because of their good comprehensive performance, being potential as lead-free alternative. Specially, a remarkable d33 value of approximately 416 pC·N−1, comparable to PZT-4, was achieved in the textured KNN-based piezoceramics based on the reactive templated grain growth (RTGG) method, as reported by Saito13. This finding attracts extensive research on the KNN system. However, the pure KNN piezoceramics typically exhibit a d33 of only 120 pC·N−1, despite the room temperature (RT) morphotropic phase boundary consisting two orthorhombic (O) perovskite phases14. To improve the piezoelectric performances of KNN system, extensive efforts have been made, including constructing the RT polymorphic phase boundary consisting O-tetragonal (T) phases or forming the polarization nanoregion (PNR) by introducing multi elements such as Ca2+, Bi3+, Hf4+, Zr4+, Ti4+, Sb5+ or other perovskite end members15,16,17,18. For example, O-T phase boundary was established at RT in the Ba-doped 0.97(K0.48Na0.52)(Nb0.96Sb0.04)O3-0.03Bax(Bi0.5Ag0.5)1-xZrO3 textured piezoceramics19, achieving a high d33 ~ 406 pC·N−1. Another study reported a high d33 = 570 ± 10 pC·N−1 in the (1-x-y)K1-wNawNb1-zSbzO3-yBaZrO3-xBi0.5K0.5HfO3 system by establishing a new rhombohedral R-T phase boundary20. Furthermore, a superior d33 ~ 650 pC·N−1 was obtained in the (0.96-x)K0.48Na0.52Nb0.95Sb0.05O3-0.04Bi0.5(Na0.82K0.18)0.5ZrO3-0.4%Fe2O3-xAgSbO3 ceramics at x = 1.6% due to the R-O-T multiphase coexistence at RT21. These results reveal that forming O-T or R-T, or R-O-T phase boundary is an effective strategy to achieve an ultrahigh d33 value in KNN-based ceramics. However, not all KNN-based piezoceramics with the polymorphic phase boundary have such a large d3313,14,15,16. For example, the d33 is only 285 pC·N−1 for (0.97- x)K0.48Na0.52NbO3-0.03Bi0.5(Na0.7K0.2Li0.1)0.5ZrO3-xBi0.5Na0.5TiO3 ceramic22 at x = 0.01, despite possessing R-T phase boundary. Additionally, Wang et al.23 reported a d33 of about 345 pC·N−1 in (0.96-x)K0.48Na0.52NbO3-0.04Bi0.5Na0.5ZrO3-xLaFeO3 ceramics at x = 0.006, also with O-T phase coexistence at RT. These examples highlight that different KNN-based ceramics with similar phase structures, such as O-T or R-T phase coexistence, can have significantly different d33 values. The reason for these variations in d33 value remains unresolved and continues to challenge the development of KNN based piezoceramics.

In addition to achieving an excellent d33 value, piezoelectric ceramics used in devices such as sensors and energy harvesters must also exhibit a high Curie temperature Tc, great temperature stability and large longitudinal electromechanical coupling factor (k33)24,25,26. Although the d33 of KNN ceramics can be greatly improved by element doping to build the polymorphic phase boundary at RT, this often comes at the cost of a reduced Tc. For example, the Tc of (0.96-x)K0.48Na0.52Nb0.95Sb0.05O3-0.04Bi0.5(Na0.82K0.18)0.5ZrO3-0.4%Fe2O3-xAgSbO3 piezoceramics which exhibit an impressive d33 of 650 pC·N−1 drops to below 200 °C, which is detrimental to real applications21. Therefore, sacrificing Tc to improve the piezoelectric of KNN-based ceramics is not a viable solution. It is highly commendable that grain orientation offers a way to achieve high d33 and large k33, while maintaining the material’s Tc27,28,29. In general, the d33 of textured ceramics can be doubled compared to random oriented ceramics without sacrifice of Tc30. However, since the underlying mechanism responsible for the d33 variation among different KNN-based ceramics with the same structure remains unresolved, the potential for improving d33 in KNN-based textured ceramics is still limited. For example, the d33 values of <001 > -textured 0.92(Na0.5K0.5)NbO3-0.06BaZrO3-0.02(Bi0.5Li0.5)TiO331 and <001 > -textured (K0.5Na0.5)0.95Li0.05Nb0.93Sb0.07O332 piezoceramics are only 271 pC·N−1 and 331 pC·N−1, respectively, which are even lower than those of many other non-textured KNN-based systems.

To address the above challenges and develop KNN-based piezoceramic with superior piezoelectric performances, a combination of the structural flexibility and grain orientation strategies were adopted in this work, as shown in Fig. 1. On the one hand, the structural flexibility can reduce the energy barrier of dipole alignment and provide multiple polarization directions, facilitating the alignment of dipole25. On the other hand, the grain orientation offers a suitable condition to promote the displacement of B-site cations leveraging the engineered domain configuration28, which are beneficial to further improving the piezoelectric properties. In order to boost the structural flexibility in the KNN system, the B5+ ions with high electronegativity are chosen in this work because they can provide a high Coulombic force to induce the lattice disorder. Figure 1a shows a 2D perovskite structure of typical KNN system. When the Nb5+ ions in the KNN system were replaced by some high-electronegativity B5+ ions, the distance between cations increases, for example r1 < r2 as shown in Fig. 1b, because of high Coulomb force between K+/Na+ ions and B5+ ions, higher than that of one between K+/Na+ ions and Nb5+ ions. The increasing cationic distance will make the cell volume enlarged and structure soften as shown in Fig. 1c. Figure 1d–f describe the polarization configurations within grain for different KNN systems, in which each small squares represent a crystal cell. The <011> and <001> polarization configurations are dominant in a standard KNN ceramic with O-T phase coexistence as shown in Fig. 1d, whereas the sample with structural flexibility also may exhibits non-<001> and non-<011> polarization configurations as shown in Fig. 1f, because of the high Coulomb force between B5+ ions and K+/Na+ ions. Figure 1g shows the polarization configurations of KNN sample with grain orientation. Because the interface energy and grain boundary energy between the template and matrix reduce, the dipole of grain-orientation KNN sample exhibits an obvious alignment.

Fig. 1: Schematic diagram of ultrahigh comprehensive piezoelectric performances of (K,Na)NbO3-based piezoceramic.
Fig. 1: Schematic diagram of ultrahigh comprehensive piezoelectric performances of (K,Na)NbO3-based piezoceramic.The alternative text for this image may have been generated using AI.
Full size image

2D structure of O-phase KNN piezoceramic along (001) face (a), interaction energy between the cation of A site and B site (b), 2D structure along (001) face when the Nb ions was replaced by the Bʹ ions whose possess a high electronegativity (c). The polarization configurations for typical KNN system with O-T two phase coexistence (d), Bʹ ions doping KNN system (e), and texture KNN one (f). Longitudinal piezoelectric coefficient d33 and k33 for R-KNN-0Sb, R-KNN-5Sb and T-KNN-5Sb ceramics (g).

Based on this understanding, we designed and investigated the (K,Na)(Nb1-xSbx)O3-Bi0.5Na0.5ZrO3-BiFeO3 (R-KNN-xSb) (0 ≤ x ≤ 7 mol%) system and its textured ceramics (T-KNN-xSb). The R-KNN-0Sb ceramic with the O-T phase coexistences has inferior d33 about 179 pC·N−1 and k33 = 52% as shown in Fig. 1g. As expected, the R-KNN-5mol% Sb (R-KNN-5Sb) ceramic, benefiting from both O-T phase coexistence and structural flexibility, achieved d33 and k33 reached to 357 pC·N−1 and 62%. Most notably, the T-KNN-5mol% Sb (T-KNN-5Sb) ceramic, incorporating O-T phase coexistence, structural flexibility, and grain orientation, exhibited exceptional piezoelectric properties (d33 ~ 807 pC·N–1, k33 = 88%) as shown in Fig. 1g. These excellent piezoelectric properties suggest the T-KNN-5Sb ceramic can replace lead-based piezoceramics in ultrasonic transducer. Additionally, pulse-echo waveforms and frequency spectra from T-KNN-5Sb/epoxy 1-3 piezoelectric composites further demonstrate its potential for transducer application, positioning it as a viable alternative to PZT piezoceramics.

Results and Discussion

To explore the atomic displacements and lattice variation in the R-KNN-0Sb, R-KNN-5Sb and T-KNN-5Sb samples, high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) was conducted along the [100]c direction, as shown in Fig. 2, Fig. S2 and Fig. S3. Multiple polarization configurations, such as <011 > , <001 > , non-<001> and non-<011> polarization configurations, are observed in the R-KNN-5Sb ceramic as shown in Fig. 2a, 2a1 and 2a2. However, for the R-KNN-0Sb ceramic, only <001> and <011> polarization configurations are present, with no evidence of non-<110> and non-<001> ones as shown in Fig. S2. This result verifies the hypothesis as shown in Fig. 1 that the introduction of high-electronegativity Sb ions (~ 2.05) to substitute the Nb ion (~ 1.6) will lead to the multiple polarization configurations generated and structural flexibility increased. On the other hand, the polarization displacement of B-site cations, defined as the intensity of spontaneous polarization, is obviously different between R-KNN-0Sb and R-KNN-5Sb ceramic, denoted by the length of the arrow as shown in Fig. S2 and 2a. The polarization displacement of B-site cations for R-KNN-5Sb ceramic is lower than that of R-KNN-0Sb one, suggesting the intensity of spontaneous polarization of the R-KNN-5Sb ceramic is lower than that of R-KNN-0Sb one. This is also due to the large Coulomb force between Sb ions and K/Na cations, far higher than that of Nb-K/Na one, making the polarization displacement of B-site cations inhibited. In a word, the introduction of high-electronegativity Sb ions in the KNN system make the crystal structure disorder and structural flexible boosted. Similar with R-KNN-5Sb ceramic, the T-KNN-5Sb ceramic also exhibits low spontaneous polarization intensity as shown in Fig. 2b and small domain size as shown in Fig. S3e and S3f, indicating that the high coulomb force effect coming from the high-electronegativity Sb ions is still present in the texture sample. However, unlike the R-KNN-5Sb ceramic, T-KNN-5Sb one displays almost exclusively <001> polarization configuration, as shown in Fig. 2b, indicating <001> orientation alignment. This <001> grain orientation is due to the decrease of the interface energy and grain boundary energy between the NN seed template and KNN-5Sb matrix.

Fig. 2: Local symmetry and polarization mapping inside nanodomains.
Fig. 2: Local symmetry and polarization mapping inside nanodomains.The alternative text for this image may have been generated using AI.
Full size image

Atomically resolved STEM HAADF image of R-KNN-5Sb (a) and T-KNN-5Sb (b) along [100], with the δNb-O displacement vector map overlaid on it; the displacement vectors are indicated as arrows; polarization directions for O and T phases are marked accordingly with I, II, III and IV. (a1) and (a2) Enlarged image of R-KNN-5Sb highlights the main regions of the O and T phases. (b1) and (b2) Enlarged image of T-KNN-5Sb highlights the main regions of the O and T phases.

To investigate the effect of the high-electronegativity Sb ions and texturization on the lattice, the a × c value, a and c parameters for the R-KNN-0Sb, R-KNN-5Sb and T-KNN-5Sb ceramics, achieved by atomically resolved STEM HAADF image, are shown in Fig. S4. The a × c value of the R-KNN-5Sb and T-KNN-5Sb ceramics is almost the same (~11.0 Å2), and larger than that of R-KNN-0Sb one (~10.8 Å2), indicating that the introduction of high-electronegativity Sb ions to substitute the Nb ion (~1.6) makes the unit cell volumes of KNN system increased. Since the ionic radius of Sb5+ ions (r ~ 0.6 Å) is lower than that of Nb5+ ions (r ~ 0.64 Å), the increase of unit cell volumes for the R-KNN-5Sb and T-KNN-5Sb ceramics should be attributed to the influence of the high-electronegativity Sb ions. Although the a × c value for the R-KNN-5Sb and T-KNN-5Sb ceramics is the same, their a and c parameters are different. The a parameter of T-KNN-5Sb sample is ~3.265 Å, shorter than that of R-KNN-5Sb one (a ~ 3.318 Å) as shown in Fig. S4b, while its c parameter (~3.322 Å) is longer than that of R-KNN-5Sb one (c ~ 3.280 Å) as shown in Fig. S4c. This result indicates that grain orientation can enlarge the c parameter of unit cell, and decreases the a one, which is beneficial to promoting the B-site ions alignment along the <001> direction. All T-KNN-xSb samples exhibit a high texture fraction (> 97%) as shown in Fig. S5 and Fig. S6.

The domain structures of the R-KNN-0Sb, R-KNN-5Sb and T-KNN-5Sb ceramics were also investigated using piezoelectric force microscopy (PFM) and phase-field simulations as displayed in Fig. 3. Large domains are observed in the R-KNN-0Sb ceramic as shown in Fig. 3a1 and 3a2. However, the domain size obviously decreases with the emergence of numerous nanodomains in the R-KNN-5Sb and T-KNN-5Sb ceramics, which contain Sb5+ ions, as shown in Fig. 3b1, 3b2, 3c1, and 3c2. For the R-KNN-5Sb ceramics, the decrease of its domain size can be attributed to several factors. First, the appearance of non-<110> and non-<001> polarization configurations disrupted the original domain structure with long ranged ordering and resulting in nanodomain formation. Second, the decrease of spontaneous polarization, corresponding to the reduced off-center displacement for B-site cations, also weakens the coupling between cells, further reducing domain size. Although the non-<110> and non-<001> directions domains are absent, the structural flexibility and low spontaneous polarization intensity still exists in the T-KNN-5Sb ceramic due to the effect of high-electronegativity Sb ions, which also makes its domain size decreased.

Fig. 3: Domain structure.
Fig. 3: Domain structure.The alternative text for this image may have been generated using AI.
Full size image

Images of PFM and phase-field simulations for R-KNN-0Sb (a), R-KNN-5Sb (b), and T-KNN-5Sb ceramics (c). Amplitude and phase patterns of PFM for R-KNN-0Sb (a1) and (a2), R-KNN-5Sb (b1) and (b2), T-KNN-5Sb (c1) and (c2) ceramics with a scanning area of 5 × 5 μm2, respectively. Polarization vectors of phase-field simulations for R-KNN-0Sb, R-KNN-5Sb and T-KNN-5Sb ceramics with O-T phase coexistence before (a3), (b3), and (c3), and after applying electric field along with Z-axis direction (a4), (b4), and (c4), respectively.

To reveal the domain response to an electric field in the R-KNN-0Sb, R-KNN-5Sb and T-KNN-5Sb ceramics, a domain writing experiment was conducted, as shown in Fig. S7. Initially, an area of 5 × 5 μm within the black box was polarized by a DC voltage of +18 V, causing the domain to completely rotate, as shown in Fig. S7a, S7c, and S7e. Then, a series of reverse DC voltages were applied to investigate their domain switching capabilities. In the R-KNN-0Sb ceramic, the domain was resistant to switching when the electric field was less −12 V, as shown in Fig. S7b. In contrast, a completely reversed domain was observed in R-KNN-5Sb sample at a low voltage about -9 V, as shown in Fig. S7d. This result confirms that the structural flexibility in the R-KNN-5Sb ceramic helps to reduce the energy barrier for polarization rotation. However, different from the R-KNN-5Sb ceramic, the switch of domain in the T-KNN-5Sb ceramic occurred only when the electric field exceeded −12 V. This result indicates that a higher energy is required to switch the aligned domains in T-KNN-5Sb ceramic, suggesting that the T-KNN-5Sb ceramic has a better thermal stability compared to the R-KNN-5Sb counterpart.

Phase-field simulations for R-KNN-0Sb, R-KNN-5Sb and T-KNN-5Sb ceramics are also illustrated in Fig. 3 to enrich the theoretical understanding of their piezoelectric response. Fig. 3a3 shows that the R-KNN-0Sb ceramic exhibits large domain size, distinct domain walls, and high spontaneous polarization. In contrast, Fig. 3b3 reveals that the R-KNN-5Sb ceramics, affected by the structural flexibility, display multiple polarization configurations, smaller domain size, lower spontaneous polarization. For the T-KNN-5Sb ceramics as shown in Fig. 3c3, both structural flexibility and grain orientation are present, making the B-site cations aligning along Z direction. After the domain structure stabilizes, an electric field up to 30 kV/cm was applied to investigate the polarization response along the Z direction for all studied ceramics, as shown Fig. 3a4, 3b4, and 3c4. The domain alignment becomes challenging in the R-KNN-0Sb ceramics due to its large domain size, distinct domain walls and high spontaneous polarization, as shown in Fig. 3a4. However, for the R-KNN-5Sb ceramics, most of domains have switched along Z direction as shown in Fig. 3b4. This is due to the fact that the domain switching becomes easier due to the structural flexibility. In the T-KNN-5Sb ceramics, on the other hand, the domains are completely aligned along Z direction as shown in Fig. 3c4, demonstrating that combination of the structural flexibility and grain orientation can effectively promote the alignment of B-site cations along the <001> orientation.

Figure 4a illustrates the piezoelectric coefficients d33 for both random and textured KNN-xSb ceramics. With the increasing x content, the d33 for both R-KNN-xSb and T-KNN-xSb ceramics initially increases before eventually decreasing. Notably, the d33 of T-KNN-xSb ceramics is about twice as higher as that of R-KNN-xSb ceramics. An ultrahigh d33 = 807 pC·N−1, representing the highest value reported for KNN ceramics to date, was achieved in the T-KNN-5Sb sample, as shown in Fig. 4a. This remarkable d33 is due to the combined effects of structural flexibility and grain orientation, which facilitate the B-site cations almost entirely align along <001> direction. Fig. 4b shows the longitudinal electromechanical coupling factor (k33). The k33 of T-KNN-xSb ceramics significantly exceeds those of R-KNN-xSb ceramics. An excellent k33 about 88 % was achieved in the T-KNN-5Sb ceramic. In addition to d33 and k33, the Tc is also an important factor affecting piezoceramic practice applications. The temperature dependent dielectric constant of random and textured KNN-xSb ceramics were illustrated in Figs. 4c and S8. There are two obvious dielectric anomalies in all samples, corresponding to the O-T and T-Cubic (C) phase transitions. The Tc of R-KNN-5Sb and T-KNN-5Sb ceramics is the same about 245 oC as shown in Fig. 4c, lower than that of R-KNN-0Sb ceramics, indicating that the introduction of Sb5+ can reduce the Tc. The O-T phase transition peak also shifts to lower temperature with increasing the x content, yet remains close to RT, indicating that all samples exhibit O-T phase coexistence at RT. Additionally, we also found that the dielectric constant of T-KNN-xSb ceramics at RT is lower than that of R-KNN-xSb ceramics. The figure of merit (d33×g33) for energy harvesting application are compared in Fig. 4d for R-KNN-xSb and T-KNN-xSb ceramics. Due to the high d33 ~ 807 pC·N−1 and large g33 value, an ultrahigh d33×g33 ∼64.7 × 10−12 m2·N−1 was also achieved in the T-KNN-5Sb ceramics, which is the highest documented value in KNN system. Fig. 4e compares the electric-field-induced strain for R-KNN-0Sb, R-KNN-5Sb and T-KNN-5Sb ceramics. Due to the structural flexibility and grain orientation, the T-KNN-5Sb ceramics also exhibit a high strain ~0.2 % and effective piezoelectric strain coefficient d33*~927 pm·V−1, surpassing the values for R-KNN-0Sb and R-KNN-5Sb ceramics. Finally, Fig. 4f provides a comparison of Tc and d33 for PZT, BaTiO3, (Bi, Na)TiO3, BiFeO3-BaTiO3, KNN-based materials and this current work. The T-KNN-5Sb ceramic demonstrates ultrahigh comprehensive piezoelectric performance with d33 ~ 807 pCN−1 and Tc ~ 245 °C.

Fig. 4: Piezoelectric, ferroelectric and dielectric preformances.
Fig. 4: Piezoelectric, ferroelectric and dielectric preformances.The alternative text for this image may have been generated using AI.
Full size image

Comparison of properties of random and texture KNN-xSb ceramic d33 (a), k33 (b), and g33×d33 (d). Temperature dependence of dielectric constant (c) and electric-field-induced strains (e) for R-KNN-0Sb, R-KNN-5Sb and T-KNN-5Sb ceramics, (all date were measured at 10 Hz). The comprehensive performance comparison of the studied ceramics with other piezoelectric ceramics (f)5,6,7,8,9,10,11,12,20,21,34.

To evaluate the practical advantages of T-KNN-5Sb ceramics, we compared R-KNN-0Sb, R-KNN-5Sb, T-KNN-5Sb and commercial PZT-5 (purchased from the Baoding Hongsheng acoustic electronic equipment Co., LTD, China)/epoxy 1-3 piezoelectric composites, prepared under the identical conditions. Figure 5a outlines the schematic procedure of the dice-and-fill method used for 1-3 composites. We assessed the echo responses of these piezoelectric composites in water, measuring their center frequency (fc) and bandwidth at -6 dB (-6 dB BW), as shown in Fig. 5b–e. The -6 dB BW and fc are calculated by the following formula: fc = (f1 + f2)/2 and -6 dB BW = (f2-f1)/fc. Here, f1 and f2 are the -6 dB low and high cut-off frequencies, respectively, where the voltage is halved. All transducers produced clear pulse echoes, but the T-KNN-5Sb/epoxy 1-3 piezoelectric composite demonstrates a significantly broader bandwidth in comparison to R-KNN-0Sb or R-KNN-5Sb counterparts. Additionally, the voltage amplitude of T-KNN-5Sb/epoxy 1-3 piezoelectric composite is higher than others, as shown in Fig. 5b–d, indicating that it possesses a higher signal sensitivity than that of R-KNN-0Sb and R-KNN-5Sb composites. This improvement is mainly due to that the T-KNN-5Sb ceramics possess ultrahigh piezoelectric coefficient (d33 = 807 pC·N−1) and high longitudinal electromechanical coupling factor (k33 ∼ 88%)33, far beyond those of R-KNN-0Sb and R-KNN-5Sb ceramics as shown in Fig.4. Moreover, the T-KNN-5Sb/epoxy 1-3 piezoelectric composite outperformed the commercial PZT-5 composite in both bandwidth and the voltage amplitude, as shown in Fig.5e. This result suggests that the T-KNN-5Sb ceramics have the potential to replace PZT-based materials in transducer applications.

Fig. 5: Applications for 1–3 composites transducers.
Fig. 5: Applications for 1–3 composites transducers.The alternative text for this image may have been generated using AI.
Full size image

Schematic procedure of the dice-and-fill method used for fabricating R-KNN-0Sb, R-KNN-5Sb, T-KNN-5Sb and commercial PZT-5 (Purchased from Baoding Hongsheng acoustic electronic equipment Co., LTD, China)/epoxy 1–3 composites for transducers (a), the Pulse-echo waveform and frequency spectrum of the ultrasonic transducer for R-KNN-0Sb (b), R-KNN-5Sb (c), T-KNN-5Sb (d) and commercial PZT-5 (e).

In summary, we designed a series of R-KNN-xSb and T-KNN-xSb ceramics, featured by O-T phase coexistence, to explore the effect of lattice and orientation on their performances. Results indicate that the introduction of high-electronegativity Sb ions to substitute the Nb ion in KNN system can makes the structural flexibility increased, while grain orientation promotes the alignment of B-site cations along the <001> orientation. Due to the synergistic effect of structural flexibility and grain orientation, T-KNN-xSb ceramics gained excellent comprehensive piezoelectric performances, including ultrahigh piezoelectric coefficient d33 = 807 pC·N−1, d33×g33 ∼64.7 × 10−12 m2·N−1 and large k33 = 88% as well as high Tc ∼ 245 °C at x = 0.05. Moreover, the superior performance of T-KNN-5Sb/epoxy 1–3 piezoelectric composite compared to commercial PZT-5 composite, suggesting that the T-KNN-5Sb ceramics have a great potential to replace the currently used PZT piezoceramics in transducer application.

Methods

The specific experimental and phase-field simulations details are provided in supporting information.