Nonergodic Relaxor Research Articles

Ultrahigh Electrostrictive Effect in Lead-Free Sodium Bismuth Titanate-Based Relaxor Ferroelectric Thick Film.

In recent years, the development of environmentally friendly, lead-free ferroelectric films with prominent electrostrictive effects have been a key area of focus due to their potential applications in micro-actuators, sensors, and transducers for advanced microelectromechanical systems (MEMS). This work investigated the enhanced electrostrictive effect in lead-free sodium bismuth titanate-based relaxor ferroelectric films. The films, composed of (Bi0.5Na0.5)0.8-xBaxSr0.2TiO3 (BNBST, x = 0.02, 0.06, and 0.11), with thickness around 1 μm, were prepared using a sol-gel method on Pt/TiO2/SiO2/Si substrates. By varying the Ba2+ content, the crystal structure, morphology, and electrical properties, including dielectric, ferroelectric, strain, and electromechanical performance, were investigated. The films exhibited a single pseudocubic structure without preferred orientation. A remarkable strain response (S > 0.24%) was obtained in the films (x = 0.02, 0.06) with the coexistence of nonergodic and ergodic relaxor phases. Further, in the x = 0.11 thick films with an ergodic relaxor state, an ultrahigh electrostrictive coefficient Q of 0.32 m4/C2 was achieved. These findings highlight the potential of BNBST films as high-performance, environmentally friendly electrostrictive films for advanced microelectromechanical systems (MEMS) and electronic devices.

The structural evolution and electric field-induced strain performance of Bi0.5(Na0.41K0.09)TiO3–Ba(Fe0.5Sb0.5)O3 lead-free piezoelectric ceramics

In recent years, lead-free Bi0.5Na0.5TiO3 (BNT) based piezoelectric ceramics with excellent strain properties have gained widespread recognition for their application in high-precision displacement actuators. The (1-x)(0.82Bi0.5Na0.5TiO3-0.18K0.5Bi0.5TiO3)-xBa(Fe0.5Sb0.5)O3 ceramics were fabricated through the die-pressing method in this work. The effect of BFS introduction on the dielectric, ferroelectric and microstructure characteristics of BNKT ceramics was systematically investigated. Among these compositions, the BNKT-0.015BFS ceramics exhibited a piezoelectric strain coefficient (d33*) of 658 pm/V at an electric field of 55 kV/cm, while achieving a strain response of 0.51 % at 85 kV/cm. The observed improvement in strain performance can be attributed to the evolution from non-ergodic relaxor state to ergodic relaxor state caused by BFS substitution. Furthermore, transmission electron microscopy (TEM) explicitly confirmed coexistence of rhombohedral and tetragonal phase and revealed the morphology of nanosized domains. This study adds to a deeper comprehension of the characteristics of strain response enhancement in BNT-based ceramics, opening up avenues for designing novel lead-free piezoelectric ceramics with outstanding electromechanical performance.

Effects of quenching on domain switching and electric field-induced phase transformations in Na0.5Bi0.5TiO3-NaNbO3 ceramics

Quenching from high temperatures has been identified as a useful means to enhance the piezoelectric properties and thermal stability of bismuth-based perovskite ferroelectrics. In the present work, it is demonstrated that quenching leads to improvement of depolarization temperature, ferroelectric and piezoelectric properties in Na0.5Bi0.5TiO3-NaNbO3 (NBT-0.1NN) ceramics. In-situ synchrotron x-ray diffraction measurements indicated an irreversible transformation from cubic to coexisting cubic and rhombohedral phases during the application of a high electric field, for both as-sintered and quenched ceramics. These results confirm the non-ergodic relaxor ferroelectric nature of the materials. DC poling induced a transformation to single-phase rhombohedral structure in both cases, with highly textured domain configurations. These well-oriented ferroelectric domain states were relatively stable under subsequent bipolar electric field cycling. For the pre-poled NBT-0.1NN ceramics, the quenched samples were found to exhibit the highest intrinsic (lattice strain) and extrinsic (domain switching) contributions to electrostrain, due to the increased rhombohedral distortion.

Giant field-induced strain with excellent fatigue performance in (Al0.5Nb0.5)4+-modified 0.85Bi0.5Na0.5TiO3-0.11Bi0.5K0.5TiO3-0.04BaTiO3 piezoelectric ceramics

Utilizing a conventional solid-state reaction procedure, (Al0.5Nb0.5)4+-modified 0.85Bi0.5Na0.5TiO3-0.11Bi0.5K0.5TiO3-0.04BaTiO3 (BNKT-BT) samples were synthesized. The impact of (Al0.5Nb0.5)4+ on the crystal structure, ferroelectric, dielectric, and AC impedance properties was systematically investigated. The XRD patterns demonstrate that the crystal structures of all samples exhibit typical pseudo-cubic features. According to the XPS, the doping of (Al0.5Nb0.5)4+ reduces the concentration of oxygen vacancies inside the ceramics, which significantly affects the relaxation properties. This substitution successfully triggers a change from a non-ergodic relaxor (NR) state to an ergodic relaxor (ER) state, which is ascribed to the weakening of the pinning effect of the oxygen vacancies on the polar nanoregions (PNRs). The ceramics exhibit an enormous monopolar strain of 0.468 % under 60 kV/cm, accompanied by an inverse piezoelectric coefficient (d33*) of 780 pm/V, surpassing the performance of numerous other BNT-based piezoelectric ceramics. After 1×104 switching cycles, the strain value changes slightly, indicating excellent fatigue performance. The considerable strain arises from a reversible transformation of the ER phase to the ferroelectric phase induced by an electric field. This research suggests that (Al0.5Nb0.5)4+-doped BNKT-BT ceramics have good prospects for application in actuators and sensors.

Optimized pyroelectric behaviors by constructing the nonergodic-ergodic transition state

Bi0.5Na0.5TiO3 (BNT)-based relaxors are considered as potential candidates for pyroelectric applications due to their excellent pyroelectric performances. However, the excellent pyroelectric response in BNT-based relaxors is generally accompanied by a rapid decrease in the depolarization temperature Td, limiting the operation temperature. Herein, we find that the mixed non-ergodic and ergodic relaxor states (a kind of transition system) can promote polarization rotation and remain the reversibility of polarization transformation simultaneously, thereby improving pyroelectric performances and maintaining the Td . The Li+-doped BNKT-based relaxors which possess such a transition state exhibit excellent room temperature (RT) pyroelectric coefficients (1247 μCm−2K−1), and also, the Td can maintain at 69℃. This work provides a strategy for further insight into the enhanced pyroelectric response, which promotes the development of eco-friendly pyroelectric applications (such as infrared detection, temperature sensors, and pyroelectric energy harvesting).

The thermal depolarization behavior of PMN-PT-BZT relaxor ferroelectric ceramics from the standpoint of domain structure transitions

The thermal depolarization behavior of PMN-PT-5BZT relaxor ferroelectric ceramics was studied, and the depolarization mechanism was discussed from the perspective of domain structure transitions. In addition to the transition from MPB structure at room temperature to cubic phase at high temperature, the structure symmetry of PMN-PT-5BZT ceramics has no obvious change with increasing temperature. However, the ceramic had experienced a transition process from ferroelectric state to nonergodic relaxor state, and then to ergodic relaxor state. The results of temperature dependence of ferroelectric properties showed that the depolarization temperature Td corresponds to the transition temperature TF-NR from ferroelectric state to nonergodic relaxor state, and there is an obvious dielectric abnormal peak at this temperature, which is mainly due to the depolarization behavior caused by the decrease of macrodomain size and the beginning of transition to nanodomains.

Realization of the Giant Pyroelectric Response via Modulated Polar Structures.

Among pyroelectric materials, Bi0.5Na0.5TiO3 (BNT)-based relaxors are particularly noteworthy due to their significant polarization fluctuation near the depolarization temperature (Td), resulting in a large pyroelectric response. What has been overlooked is the dynamic behavior of inherent polar structures, particularly the temperature-dependent evolution of polar nanoregions (PNRs), which significantly impacts the pyroelectric behavior. Herein, based on the large pyroelectric response origination (the ferroelectric-relaxor phase transition), the mixed nonergodic and ergodic relaxor (NR+ER) critical state is constructed, which is believed to trigger the easily fluctuating polarization state with excellent pyroelectric response. Composition engineering (with Li+, Sr2+, and Ta5+) strategically controls the relaxor process and modulates the dynamic behavior of inherent polar structures by the random field effect. The pyroelectric coefficient of more than 1441 µCm-2K-1 at room temperature (RT), more than 9221 µCm-2K-1 (RT), and ≈107911 µCm-2K-1 (Td) are achieved in the Li+-doped sample, the Sr2+-doped sample, and the (Li++Ta5+) co-doped sample, respectively. This work earns the highest RT pyroelectric coefficient in BNT-based relaxors, which is suitable for pyroelectric applications. Furthermore, it provides a strategy for modulating the pyroelectric performance of BNT-based relaxors.

Phonon mode and dielectric function dynamics of Bi0.5Na0.5TiO3-xSm2Ti2O7 ceramics during the phase transitions discovered by Raman scattering and spectroscopic ellipsometry

Recently, Bi0.5Na0.5TiO3-based ceramics have drawn widespread attention due to their excellent energy storage properties. Here, a comprehensive analysis of the composition- and temperature-driven transition processes in (1 − x)Bi0.5Na0.5TiO3-xSm2Ti2O7 (BNST-x) polycrystals have been presented using Raman scattering and spectroscopic ellipsometry. With increasing Sm2Ti2O7 content, BNST-x ceramic gradually becomes disordered and belongs to the superparaelectric state at x = 0.12 near room temperature. Moreover, the thermal evolution of the lattice kinetic behaviors shows two crucial temperatures: the depolarization temperature Td and the temperature at the maximum dielectric permittivity Tm, which suggest the transitions from nonergodic relaxor ferroelectric—ergodic relaxor (ER) ferroelectric and ER ferroelectric—superparaelectric, respectively. It is noteworthy that the series of changes is closely related to the ordering degree of the B-site ion affected by the doping and the temperature. This work gives an insight into the connection among the phonon behavior, electronic transition, and lattice structure of BNST-x ceramics, which can further understand the phase transition mechanisms under the doping and thermal field.

Successive phase transitions–induced multiple boundaries and unprecedented electrocaloric effect in Pb(Yb1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3 system

AbstractTemperature stability of electrocaloric effect (ECE) is a thorny problem in ferroelectrics (FE). A general method is to design ferroelectric‐to‐relaxor phase transition at a sacrifice of electrocaloric (EC) strength. The Pb(Yb1/2Nb1/2)O3 antiferroelectrics (AFE) + Pb(Mg1/3Nb2/3)O3 relaxors strategy designed in this work is effective to tackle this dilemma [(1 − x)PYN–xPMN, x = 0.08–0.36]. PMN addition induces a successive phase transition and dual phase boundaries of ferrielectric (FIE)‐nonergodic relaxor (NER) and NER‐ergodic relaxor (ER), where ferroelectric polarization/strain and ECE reach a local maximum. Thermally stable ΔT is unexpectedly achieved in FIE (x = 0.14) and NER (x = 0.24), except for a generality for ER state (x = 0.30). A dome‐like variation trend is observed in x = 0.14 and 0.24 with a wide temperature span of ∼60 and ∼55 K (±15%ΔTmax). Notably, x = 0.24 NER possesses a large directly measured ΔTmax ∼0.64 K simultaneously. Dielectric/ferroelectric properties clarify that two‐stage transition of AFE rigid‐order de‐texture and dissociation of de‐textured AFE domains into polar nano‐entities accounts for thermal stability of ΔT as the alternation of ordered antipolar domains to disorder relaxors serves as a buffer to compensate for the thermal‐shock enhanced random field. This work not only accounts for the underlying mechanism for thermal stability of ΔT at FIE and NER side for the first time in physics but also provides an exotic approach to seek for high‐performance EC materials in practical applications.

Phase Structure, Microstructure, and Electrical Properties of Bi0.47Na0.47Ba0.06TiO3 Ceramics with (LiNb)4+ Substituted into B-Sites

Due to the substitution of complex ions into B-sites is very interesting in recent, lead-free Bi0.47Na0.47Ba0.06Ti1− x (LiNb) x O3 (BNBT1− x LN x ) ceramics (with x = 0–0.04) were fabricated by the solid-state combustion method. The influence of (LiNb)4+ (x) on the phase structure, microstructure, and electrical properties was investigated. The X-ray diffraction (XRD) patterns exhibited a pure perovskite structure for all specimens. Coexisting rhombohedral and tetragonal phases were observed in all samples and the tetragonal phase increased with increased x, as analyzed by the Rietveld refinement method. The morphology of the BNBT1− x LN x ceramics, obtained by scanning electron microscopy (SEM), revealed almost-round grain shapes and anisotropic grain growth. The density and average grain sizes decreased from 5.84 to 5.54 g/cm3 and 1.7 to 0.9 µm, respectively, when x increased from 0 to 0.04. The grain size distribution decreased with increased (LiNb)4+ content. A reduction in the dielectric properties was observed, due to the phase ratio changing away from a morphotropic phase boundary (MPB), an inferior microstructure, and low density caused by (LiNb)4+ substitution. The (LiNb)4+ substitution induced the transition from non-ergodic relaxor to ergodic relaxor ferroelectric state.

Electric field-temperature phase diagram and electrical properties of (1-x)Na0.5Bi0.5TiO3 - xK0.5Bi0.5TiO3 ceramics

Electrically and thermally induced transitions between ferroelectric and relaxor states are of great significance in Na1/2Bi1/2TiO3 (NBT)-based materials due to their remarkable similarity to electromechanical properties. However, an in-depth understanding of the family of this material remains challenging, primarily due to its structural complexity and diverse behaviour with or without the presence of an external electric field. For enhancing NBT-based ceramics and enabling the analysis of their electric field temperature (E-T) phase diagrams, it has been suggested that K0.5Bi0.5TiO3 (KBT) could be used as a dopant material. This study thoroughly examines the electrical, microstructural, and ferroelectric (FE) properties of (1-x)NBT-xKBT ceramics. The incorporation of KBT into NBT, inducing a change in structural symmetry, reveals the coexistence of rhombohedral and tetragonal phases (x ∼ 0.2), as confirmed by X-ray diffraction. Using a modified KWW function, electrical modulus (EM) analysis illustrates a non-Debye-type relaxation process. Moreover, it is observed that temperature influences the transition of the material among its ferroelectric (FE), ergodic (ER), and non-ergodic (NR) relaxor phases. This report proposes that the E-T phase diagram can serve as a valuable tool for determining optimal conditions and selecting materials for electromechanical and actuator-based applications.

Optimized Strain Response in (Co0.5Nb0.5)4+-Doped 76Bi0.5Na0.5TiO3-24SrTiO3 Relaxors

High strain with low hysteresis is crucial for commercial applications in high precision actuators. However, the clear conflict between the high strain and low hysteresis in BNT-based ceramics has long been an obstacle to actual precise actuating or positioning applications. To obtain piezoceramics with high strain and low hysteresis, it is necessary to enhance the electrostrictive effect and develop an ergodic relaxor (ER) and nonergodic relaxor (NR) phase boundary under ambient conditions. In this work, (Co0.5Nb0.5)4+ doped 76Bi0.5Na0.5TiO3-24SrTiO3 (BNST24) relaxors were fabricated using the conventional solid state reaction route. X-ray diffraction patterns revealed the B-site substitution in BNST24 ceramics. By adjusting the (Co0.5Nb0.5)4+ doping in BNST24, we effectively tuned the TNR-ER and Td close to ambient temperature, which contributed to the development of the ergodic relaxor phase and enhanced the electrostrictive effect at ambient temperature. The I-P-E loops and bipolar strain curves verified the gradual evolution from NR to ER states, while the enhanced electrostrictive effect was verified by the nearly linear S-P2 curves and improved electrostrictive coefficient of the BNST24-xCN relaxors. An enhanced strain of 0.34% (d*33 = 483 pm/V) with low hysteresis of 8.9% was simultaneously achieved in the BNST24-0.02CN relaxors. The enhanced strain was mainly attributed to the proximity effect at the ER and NR phase boundary of BNST24-0.02CN, while the improved electrostrictive effect contributed to the reduced strain hysteresis. Our work demonstrates an effective strategy for balancing the paradox of high strain and low hysteresis in piezoceramics.

Ultra-high energy storage performance in Bi5Mg0.5Ti3.5O15 film via a low temperature-induced ergodic relaxation state

Good low-temperature energy storage characteristics are conducive to the successful merger of Si-based semiconductor technology with dielectric energy storage films. Due to low maximum polarization intensity and poor crystallinity at low temperatures, however, it is difficult for dielectric energy storage films to attain excellent dielectric energy storage properties. Herein, Bi5Mg0.5Ti3.5O15 films accomplish the shift from a non-ergodic relaxor state to an ergodic relaxation state by lowering the annealing temperature, which simultaneously increases insulating characteristics. The energy loss is reduced while maintaining a high polarization intensity and high breakdown electric field, which results in the ultra-high energy storage density (122.2 J/cm3) and efficiency (77.3 %) of the Bi5Mg0.5Ti3.5O15 film at an annealing temperature of 500 °C. Meanwhile, the Bi5Mg0.5Ti3.5O15 films show excellent stability in terms of temperature (−20 °C to 150 °C), frequency (0.05 kHz–20 kHz), and fatigue resistance (1 ×108). The domain states and insulation properties of temperature-controlled films are used in this work to achieve ultra-high energy storage properties, and a concise and feasible scheme for the application of low temperature energy storage films in semiconductor technology is provided.

Giant dynamic electromechanical response via field driven pseudo-ergodicity in nonergodic relaxors

Enhanced electromechanical response can commonly be found during the crossover from normal to relaxor ferroelectric state, making relaxors to be potential candidates for actuators. In this work, (Pb0.917La0.083)(Zr0.65Ti0.35)0.97925O3 ceramic was taken as a case study, which shows a critical nonergodic state with both double-like P-E loop and irreversible relaxor-normal ferroelectric phase after poling at room temperature. The low-hysteresis linear-like S-P2 loop, in-situ synchrotron X-ray diffraction and transmission electron microscope results suggest that the nonpolar relaxor state acts as a bridge during polarization reorientation process, accompanying which lattice strain contributes to 61.8% of the total strain. In other words, the transformation from normal ferroelectric to nonergodic relaxor state could be triggered by electric field through polarization contraction, which could change to be spontaneously with slightly increasing temperature in the nonergodic relaxor zone. Therefore, pseudo-ergodicity in nonergodic relaxors (i.e. reversible nonergodic-normal ferroelectric phase transition) driven by periodic electric field should be the main mechanism for obtaining large electrostrain close to the nonergodic-ergodic relaxor boundary. This work provides new insights into polarization reorientation process in relaxor ferroelectrics, especially phase instability in nonergodic relaxor zone approaching to freezing temperature.

Distinct microstructure and property evolution of 0.76(Bi0.5Na0.5)TiO3-0.24SrTiO3 ferroelectric ceramics synthesized with different TiO2 reactants

Single phase 0.76(Bi0.5Na0.5)TiO3–0.24SrTiO3 ferroelectric ceramics have been synthesized with homogenous anatase and hierarchical rutile TiO2 raw reactants (BNST-A and BNST-R). Either calcined powder persists the microstructure characteristics of raw reactants. As the result, when the sintering temperature increases from 1000 to 1200 °C, the average grain size and density of BNST-A increase from 0.49 to 1.48 μm and 5.02 to 5.61 g/cm3, while those of BNST-R from 0.86 to 1.44 μm and 5.37 to 5.61 g/cm3. BNST-A illustrates a predominant ergodic relaxor state, and BNST-R prefers a non-ergodic relaxor state, as evidenced by the distinct polarization-electric field loops and current-electric field curves. Especially, such a distinct ferroelectric state is independent of sintering temperature. It is believed that the special hierarchical microstructure of rutile TiO2 reactant is beneficial to form denser ceramics with larger grains, and thus suppresses the contributions of polar nanoregions and defect-induced built-in field to ferroelectric property, leading to non-ergodic relaxor state. This work clearly demonstrates the nonnegligible effects of TiO2 reactants on the microstructure and properties of BNST ferroelectric ceramics.

Electrostatic energy storage performances of La(Ni2/3Ta1/3)O3‐modified Na0.5Bi0.5TiO3 lead‐free ceramics

AbstractCeramic capacitors with high electrostatic energy storage performances have captured much research interest in latest years. Sodium bismuth titanate (Na0.5Bi0.5TiO3)‐based ferroelectric ceramics show great potential due to their environment‐friendly composition, high polarization, and excellent relaxor properties. However, the nonergodic relaxor state of Na0.5Bi0.5TiO3‐based ceramics hampers the decrement of remanent polarization, leading to poor energy storage performance. Herein, the (1 − x)Na0.5Bi0.5TiO3–xLa(Ni2/3Ta1/3)O3 ceramics were designed to generate the transformation between nonergodic and ergodic relaxor state. As a result, the ceramics exhibit improved dielectric relaxation, slim polarization–electric field loops, and flattened current–electric field curves due to highly dynamic polar nanoregions. Particularly, the 0.85Na0.5Bi0.5TiO3–0.15La(Ni2/3Ta1/3)O3 ceramics show large breakdown electric field Eb (345 kV/cm), high recoverable energy density Wrec (3.6 J/cm3), and efficiency η (80.6%), revealing potential applications in electrostatic energy storage.

Electric-field-induced non-ergodic relaxor to ferroelectric transition in BiFeO3-xSrTiO3 ceramics.

While BiFeO3-based solid solutions show great promise for applications in energy conversion and storage, realizing this promise necessitates understanding the structure-property relationship in particular pertaining to the relaxor-like characteristics often exhibited by solid solutions with polar-to-non-polar morphotropic phase boundaries. To this end, we investigated the role of the compositionally-driven relaxor state in (100 - x)BiFeO3-xSrTiO3 [BFO-xSTO], via in situ synchrotron X-ray diffraction under bipolar electric-field cycling. The electric-field induced changes to the crystal structure, phase fraction and domain textures were monitored via the {111}pc, {200}pc, and 1/2{311}pc Bragg peaks. The dynamics of the intensities and positions of the (111) and (111̄) reflections reveal an initial non-ergodic regime followed by long-range ferroelectric ordering after extended poling cycles. The increased degree of random multi-site occupation in BFO-42STO compared to BFO-35STO is correlated with an increase of the critical electric field needed to induce the non-ergodic-to-ferroelectric transition, and a decrease in the degree of domain reorientation. Although both compositions show an irreversible transition to a long-range ferroelectric state, our results suggest that the weaker ferroelectric response in BFO-42STO is related to an increase in ergodicity. This, in turn, serves to guide the development of BFO-based systems into promising platform for further property engineering towards specific capacitor applications.

A combination of large unipolar electrostrain and d33 in a non-ergodic relaxor ferroelectric

One of the important requirements for piezoelectric materials for use as high strain actuators is that they exhibit large unipolar electrostrain with minimum hysteresis. While large unipolar electrostrain >1% is generally achievable in good quality single crystals, most polycrystalline piezoelectric show low values < 0.4%. Unipolar electrostrain 0.5%–0.7% in polycrystalline piezoelectrics has often been reported in Na0.5Bi0.5TiO3-based compositions at the non-ergodic ergodic boundary. Not amenable to poling, such materials exhibit almost nearly zero direct piezoelectric coefficient (d33 ∼ 0 pC/N) and cannot be simultaneously used as a sensor. In this paper, we report a combination of large unipolar electrostrain of ∼0.6% with small strain hysteresis of 25% in a Sn-modified relaxor ferroelectric system PbTiO3–Bi(Ni1/2Zr1/2)O3. It exhibits d33 ∼ 340 pC/N, which is stable up to 130 °C, and large signal converse piezoelectric coefficient d33* ∼ 1200 pm/V. A combination of large d33 and d33* in the same material makes it an important candidate for simultaneous use as a sensor and high strain actuators. X-ray diffraction study in situ with the electric field suggests that large electrostrain with low strain hysteresis in this system is because of the increased reversible switching of the field stabilized tetragonal ferroelastic domains.

Decoding the correlation between initial polarity and strain property of BNT-based ceramics

Although a large electric-induced strain has been obtained in sodium bismuth titanate (Bi0.5Na0.5TiO3, BNT)-based ceramics using chemical modifications, the effect of initial BNT-based ceramic's polarity on modulating strain properties was rarely reported. Herein, we comparatively studied the effect of tantalum (Ta) doping on two BNT-based ceramics with different ferroelectric polarities, namely, (Bi0.5Na0.5)0.935Ba0.065TiO3–0.7%Bi2FeCrO6 and (Bi0.98Gd0.02)0.5Na0.5TiO3. The former locates at the morphotropic phase boundary (MPB), whereas the latter is close to pristine BNT ceramics. An effective critical point, located at the crossover between ferroelectric and relaxor, is constructed in the former ceramic and significantly enhances strain properties, whereas a useless one is found in the latter ceramic due to the retention of a non-ergodic relaxor and has merely limited ability to promote strain properties. Our results demonstrate that the ferroelectric polarity of the initial BNT-based ceramic matrix also plays an important role in pursuing high strain properties.

Spatially-resolved relaxor to ferroelectric phase switching in 0.93Na1/2Bi1/2TiO3-0.07BaTiO3 ceramics

In situ, spatially-resolved synchrotron X-ray diffraction was utilized to investigate the electric field-induced heterogenous phase transformation of nonergodic relaxor 0.93Na1/2Bi1/2TiO3-0.07BaTiO3 ceramics. A Cu electrode was coated on one surface of a rectangular sample by aerosol deposition (AD), while a Pt layer was deposited on the opposite surface by sputter deposition. It is anticipated that a different stress state and/or domain morphology should occur on the AD deposited Cu electrode side due to the particle impact-consolidation deposition process. Under an electric field, different sample regions, i.e., AD, Middle, and Sputter sides, showed systematic changes in the relaxor to ferroelectric phase transition behavior. In particular, most <001> grains transformed at a sub-coercive field of 0.8 kV/mm, while the majority of the <111> grains only appeared to undergo transitions at a higher field (2.4 kV/mm). Also, the tetragonal phase became the dominant structure at higher field levels. Importantly, both <111> and <001> grains undergo phase switching at lower fields in the region close to the AD-processed layer. The study indicates that the AD process-induced stress can facilitate the electric field-induced relaxor to ferroelectric phase transition, i.e., the AD Cu side showed more significant lattice strain and domain texture than the sputter Pt side.