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K0.5Na0.5NbO3 (KNN) crystals have great application prospects due to their excellent piezoelectric properties, high Curie temperature, and environmental friendliness. Currently, KNN crystals grown by the seed-free solid-state crystal growth (SFSSCG) method exhibit relatively high dielectric loss. In order to reduce their dielectric loss, Cu, Bi and Mn co-doped KNN lead-free piezoelectric single crystals were prepared by the SFSSCG method. The effects of the CuO doping content on the structure and electrical properties of (1 − x)(0.996KNN–0.004BiMnO3)–xCuO crystals were systematically studied. The results show that an appropriate doping amount of CuO is beneficial for the growth of the crystals and the improvement of electrical properties. When the diameter of the billets is 40 mm, the maximum crystal size of 25 × 21 × 2 mm3 is obtained. All crystals have a typical perovskite structure almost with a single orthorhombic phase and are very compact almost without holes. The minimum average domain width of 276 nm is obtained for the crystal at x = 0.005. The KNN crystals exhibit normal ferroelectric characteristics and a space-charge-limited-conduction (SCLC) mechanism. The introduction of Cu2+ ions reduces the dielectric loss of the crystal and increases its piezoelectric and dielectric properties. The Cu, Bi and Mn co-doped KNN crystals achieve excellent comprehensive properties: d33 = 314 pC N−1, Pr = 29.9 μC cm−2, Ec = 10.1 kV cm−1, = 869 pm V−1, Qm = 56.8, Kt = 0.38, tan δ = 0.013 and TC = 409 °C. This provides a route to improve the electrical properties of KNN-based crystals. [ABSTRACT FROM AUTHOR]

One of the crucial issues in developing lead-free piezoelectric materials for actuator applications lies in how to achieve large strain responses. Herein, a strategy that strengthens the synergistic contribution of reversible phase transition and ferroelectric domain switching via modulating the ferroelectric-to-relaxor transition temperature (TF−R) was proposed to improve the strain level. Following this strategy, an enhanced strain response was attained by introducing Bi(Zn2/3Ta1/3)O3 (BZT) into Bi0.5(Na0.8K0.2)0.5TiO3 (BNKT) matrix. The enhanced bipolar strain (Sbi) of 0.50% and the unipolar strain (Suni) of 0.56% were obtained in BNKT-0.025BZT ceramic, respectively, with corresponding normalized strain d33* values of 833 and 933 pm/V (@60 kV/cm). Besides, BNKT-0.05BZT ceramic exhibited excellent energy storage behavior with a recoverable energy storage density Wrec of 1.05 J/cm3 at 90 kV/cm. These findings demonstrate that BNKT-xBZT ceramics are promising material candidates for actuators and energy storage applications. [ABSTRACT FROM AUTHOR]

One of the inherent disadvantages of Bi0.5Na0.5TiO3‐based (BNT‐based) piezoceramics is that an increment of the depolarization temperature (Td) is generally accompanied by a deterioration of the temperature stability of the real‐time piezoelectric constant (d33), which severely restricts the practical applications of the materials. Herein, we propose a new strategy to mitigate the conflict between the elevation of Td and the temperature stability of the real‐time d33 in BNT‐based ceramics via integrating the pressure‐assisted sintering and quenching process. By this strategy, we not only increased the Td from 109 to 166°C but also improved the temperature stability of the real‐time d33 (the temperature coefficient Ttc = ± 13 pC/N) in 0.94Bi0.5Na0.5TiO3–0.06BaTiO3 ceramic. Both the built‐in field and the increment of the field‐induced R3c phase fraction play the significant role in enhancing the Td and the temperature stability of the real‐time d33. Thus, our work provides a simple and effective approach for designing piezoceramics with high Td and a superior temperature stability of the real‐time d33. [ABSTRACT FROM AUTHOR]

Simultaneously promoting piezoelectric constant (d33) and depolarization temperature (Td) is often incompatible in BNT-based piezoceramics. Mediating the contradiction of d33 and Td by complex chemical composition and thermal treatment methods severely restricts the development and practical applications of this kind of promising material. In this study, a sustainable plain approach to advancing materials without changing chemical compositions and preparation process is proposed, i.e., a considerable improving Td from 180 to 205 °C with significantly enhancing d33 from 135 to 162 pC/N is achieved in unmodified 0.935(Bi0.5Na0.5)TiO3–0.065BaTiO3 (BNTBT65) ceramics only by simply varying the sintering temperature. The advance in simultaneously achieving a large d33 and a high Td, which goes far beyond the performance boundary limit of d33vs. Td for BNT–BT-based systems, originates from the synergistic effect of increasing εr and grain size and oxygen vacancy. This work provides a facile way to effectively widen working temperature range and simultaneously enhanced piezoelectric properties of BNT-based piezoceramics materials for practical applications and expects to benefit other lead-free piezoelectric materials.Kindly check and confirm the edit made in the title.Yes, we have Kindly checked and confirmed the title and made no changes. [ABSTRACT FROM AUTHOR]

Piezoactuators with high electric field-induced strain are critical devices widely used in electrical systems. However, ferroelectric ceramics featuring with typical butterfly strain–electric field (S–E) loops can output only a part of the maximum attainable strains due to irreversible domain reorientation-induced negative strain. Here, a sprout-shaped strain loop with a negligible negative strain was achieved by NaNbO3-modified 0.93Bi0.5Na0.5TiO3–0.07BaTiO3 lead-free electro-strain ceramics. As NaNbO3 doping level increased to 0.02, a maximum strain (Smax) 0.45% with a high normalized strain d33* of 750 pm/V was realized with a transition to an ergodic relaxor behavior. The pinched ferroelectric hysteresis loop and rapid drop of small signal d33 demonstrated that the significant enhancement in the maximum usable strain originated from composition driving incipient piezoelectricity with reversible domains switching (ergodic state). Particularly, superior temperature stability of strain value with a fluctuation less than 3% in the temperature range of 30–150 °C was achieved. This work provides an effective way to enhance the attainable strains with excellent stability that can be applied to develop a new generation of eco-friendly actuators. [ABSTRACT FROM AUTHOR]

Dielectric capacitors have attracted extensive attention due to their high power density along with fast charge/discharge rate. Despite the high energy storage performance were obtained in lead-based ceramics, we still need to find lead-free ceramic alternatives considering the environmental requirements, and AgNbO3 has received extensive attention owing to its ferroelectric–antiferroelectric (FE–AFE) phase transition. In our study, the AFE properties of the samples were improved by tuning the grain size and polarizability of ions, and excellent energy storage performance was obtained in Bi/Ta co-doped AgNbO3. The BANT ceramic exhibited a remarkably enhanced recoverable energy density of 3.9 J/cm3 and acceptable efficiency of 61%. Morphological and structural analyses and electrical properties revealed that this co-substitution can optimize the AFE properties of the material, which can be demonstrated by the slim P–E loops and the reduced grain sizes. Of note, the BANT6 ceramic exhibited fast discharge speed accompanied by the actual energy storage density of up to 3.5 J/cm3 under 260 kV/cm. These findings indicate that AgNbO3-based AFE ceramics are a prospective alternative for energy storage materials applied to high-pulse-power fields. [ABSTRACT FROM AUTHOR]

Huge field-induced strain with low hysteresis in piezoelectric ceramics is very important for actuator. The (1-x)Bi0.5Na0.5TiO3-xSr0.7Ca0.3TiO3-0.2wt%MnO2 lead-free ceramics were prepared by solid-state reaction method. The critical composition of x = 0.45 shows the transition from ferroelectric phase to relaxor phase. The 0.55BNT-0.45SCT ceramic achieves huge strain of 0.64% with 61% strain hysteresis and shows a large signal piezoelectric coefficient (d33*) of 486 pm/V. Particularly, the 0.5BNT-0.5SCT ceramic achieves large strain of 0.42% with low strain hysteresis of 20.5%. The excellent strain properties derive from the phase transformation between relaxor phase and ferroelectric phase. These results indicate that the paraelectric SCT component can significantly enhance the field-induced strain of BNT-based piezoelectric ceramics. [ABSTRACT FROM AUTHOR]

Lead-free relaxor-ferroelectric (Mg1/3Nb2/3)4+ complex ions modified (Bi0.5Na0.5)0.94Ba0.06TiO3 (BNBT-xMN) ceramics were fabricated by traditional solid-phase reaction sintering, and the effects of (Mg1/3Nb2/3)4+ complex ions on the structural, ferroelectric, dielectric, energy storage, and strain properties of these ceramics were studied. All of the samples illustrated a single perovskite phase with a pseudo-cubic structure. Electric field-induced polarization and strain hysteresis loops indicated the occurrence of reversible ferroelectric-to-relaxor phase transition, which gave rise to a large strain of 0.49%. (Mg1/3Nb2/3)4+ complex ions greatly influenced the coercive field and remanent polarization of the ceramics; these properties also affected energy storage density of the materials. The optimal energy storage density and efficiency of the ceramics were 0.54 J/cm3 and 38.4%, respectively, when x = 0.04. These results may stem from the electric field-induced transition between the ferroelectric and relaxor-ferroelectric phase of the proposed ceramics. [ABSTRACT FROM AUTHOR]

Large Na0.5K0.5NbO3 ( NKN) piezoelectric single crystals were obtained by seed-free solid-state crystal growth method, which is a traditional sintering grain growth process, with LiBiO3 used as a sintering aid. The largest dimension of the single crystals obtained was 11 mm × 9 mm × 3 mm. In addition to the LiBiO3 doping content, temperature, and time effect of the crystal growth process was systematically investigated and considered from the kinetics point of view. With the assistance of Avrami analysis, parameters relevant to the crystal growth process were determined. Laue diffraction and transmission electron microscopy suggested an orthorhombic symmetry for the single crystalline structure. Dielectric-frequency-temperature measurements revealed an orthorhombic-tetragonal and tetragonal-cubic phase transition at 155°C and 405°C, respectively, both of which are typical of first-order transitions, and have a well-defined thermal hysteresis. Rayleigh analysis was performed regarding to the extrinsic reversible and nonreversible piezoelectric properties, and the result suggested a dominant intrinsic reversible piezoelectric contribution of 91.5% under E0 = 1 kV/cm AC amplitude. Such a single crystal growth process route is low cost and a relative simple preparation process. [ABSTRACT FROM AUTHOR]

Following increased environmental concerns on the toxicity of lead, the discovery of ultrahigh piezoelectricity in lead-free piezoelectric materials is critical for the substitution of commercial lead zirconate titanate (PZT) ceramics in numerous electronic devices. In this work, a synergistic design strategy is proposed to enhance the piezoelectricity in lead-free piezoelectric materials by flattening the Gibbs free energy density profile, via the coexistence of multiple phases and local structural heterogeneity. This strategic material design approach is based on first-principles calculations combined with Landau phenomenological theory and phase field simulations. Sustainable Stannum-doped BaTiO 3 lead-free ferroelectric ceramics are prepared to validate our proposed mechanism, and a giant piezoelectric coefficient d 33 > 1100 pC/N is achieved, being the highest value reported in lead-free piezoceramics. The mechanism and paradigm of the excellent piezoelectricity achieved here provides a feasible solution for replacing lead-based piezoelectrics by lead-free counterparts. Image 1 • A synergetic design strategy to design novel lead-free piezoelectrics with ultrahigh piezoelectricity. • A giant piezoelectric coefficient d 33 > 1100 pC/N is achieved, being the highest value reported in lead-free piezoceramics. • The mechanism and paradigm provide a feasible solution for lead-free materials of replacing lead-based counterparts. [ABSTRACT FROM AUTHOR]

Ultrahigh electrostrain (S m) at low driving field in lead-free piezoceramics could alleviate key concerns by reducing energy consumption and the risk of electrical breakdown for advanced applications. However, the giant electrostrain always accompanied with an extremely large drive field is a long-standing conflict referred as the strain-electric field trade-off. Herein, we engineer a novel strategy of introducing the B-site unequal double doping cations (ZnSn 0.5)4+ into (Bi 0.5 Na 0.5) 0.93 Ba 0.07 TiO 3 ceramic to generate the spontaneous phase transition from relaxor state to ferroelectric state, polar nanoregions PNRs and defect cluster. The giant strain of S m = 1.12% is achieved by integrating the field-induced phase transition, morphotropic phase boundary MPB and the enhanced synergistic effect between the spontaneous polarization P s and the defect cluster polarization P d under a low electric field of 50 kV/cm, thus yielding extremely large piezoactuation constant d 33 * =2240 pm/V in (Bi 0.5 Na 0.5) 0.93 Ba 0.07 Ti 0.97 (ZnSn 0.5) 0.03 O 3 piezoceramics. This finding also demonstrates an unexpected new route to design novel ferroelectric materials via nonconventional mechanisms. [ABSTRACT FROM AUTHOR]

It is difficult to obtain high d 33 and d 33 * simultaneously in one piezoelectric ceramic system via a conventional method due to the conflicting structure–properties responding mechanism between the direct piezoelectric and converse piezoelectric effects. In this work, a synergistic approach of constructing morphotropic phase boundary and introducing the internal bias fields in (Bi 0.5 Na 0.5)TiO 3 ceramics is proposed through Sr2+ and Li+ doping for mitigating the conflict between d 33 and d 33 *. By this strategy, both high d 33 (197 pC/N) and d 33 * (1500 p.m./V) are realized in Sr x (Bi 1-x Na 0.97-x Li 0.03) 0.5 TiO 3 when x = 0.24. The large d 33 stems from rhombohedral and tetragonal (R3c and P4bm) phase coexistence. The internal bias field introduced by defect dipoles tends to counteract the effects of depolarization field, thus greatly aiding the external fields with higher actual excitation fields. The superposition of internal bias field, depolarization field and external fields yields strong asymmetry bipolar strain curves, thereby contributing to the large d 33 *. Thus, this work opens a new door for developing lead-free ceramics with excellent piezoelectric performance. [ABSTRACT FROM AUTHOR]

A notoriously unresolved conflict that the substantial increment of depolarization temperature T d was generally accompanied by the sharply deterioration of piezoelectric constant d 33 in Bi 0.5 Na 0.5 TiO 3 -based (BNT-based) piezoceramics severely limit their practical applications. Herein, a new strategy by Ba2+ gradient diffusion layer in 0.94Bi 0.5 Na 0.5 TiO 3 -0.06BaTiO 3 (BNT-6BT) ceramic via interface-diffused sintering to suppress the ferroelectric-relaxor phase transition is presented to manipulate the incompatibility of T d and d 33. By this strategy, the compositionally graded diffusion in the BNT-6BT ceramic can offer both the properties simultaneously with the T d deferring from 109 °C to 170 °C and maintaining the initial d 33 (145pC/N). Furthermore, by integrating the interface-diffused sintering and quenching process, the T F-R is significantly deferring from 115 °C to 214 °C while the d 33 * is retaining the initial value (d 33 *=S max /E max =258 pm/V). Diffusion phase transition caused by Ba2+ concentration gradient promotes the greatly increased tetragonal phase ratio and the development of built-in field thereby leading to well-balanced performance between T d and d 33 in BNT-6BT ceramic. Our work opens a new avenue for developing the high-performance lead-free BNT-based piezoceramics. [ABSTRACT FROM AUTHOR]

Ferroelectric ceramics with high electrostrain have been widely applied in actuators and sensors for their rapid response and precision. However, the current bottleneck is the inability to obtain superior electrostrain values along with high piezoelectric strain coefficient (d 33 *), limiting the practical applications. Herein, we report a remarkable enhancement of electrostrain values and d 33 * simultaneously in (Bi 0.5 Na 0.5) 0.93 Ba 0.07 Ti 1- x (Nb 0.5 Ga 0.5) x O 3 (BNBT- x NG, 0 ≤ x ≤ 0.06) ceramics with the integration of nonergodic/ergodic relaxor (NER/ER) boundary and defect engineering at room temperature. This strategy by combining NER/ER boundary and defect engineering allow for highly asymmetric strain-electric field (S-E) loops with an ultrahigh and temperature-insensitive electrostrain of 0.73% as well as giant piezoelectric strain coefficient of 913 pm/V simultaneously. The electrostrain value is greater than most of the reported lead-free ceramics and even exceeds those of conventional lead-based materials. This work suggests an effective method for developing new lead-free ceramics to achieve high piezoelectric response. [ABSTRACT FROM AUTHOR]

State-of-the-art ferroelectric materials with large field-induced strain together with low hysteresis are required in high precision or positioning devices. However, the high electro-strain is always suffered from a large strain hysteresis, severely restricting its practical application. In this study, the relaxor temperature (T f) of BNT-6BT near the morphotropic phase boundary with initially high polarization was adjusted to near room temperature by adding Sr 0.7 La 0.2 TiO 3. The room temperature relaxation properties feature with the high dynamic polar nanoregions with moderate polar spatial correlations, which paired the high strain (0.325%) and ultra-low hysteresis (8.02%). This actuation strain is superior to those of previously reported lead-free piezoelectric materials. Meanwhile, the strain responses also displayed outstanding temperature and frequency stability from 30°C to 150 °C and 1 Hz–25 Hz, respectively, indicating its practical application potential. The results will provide new insight into the design of high-performance BNT-based ceramics for use in actuators. [ABSTRACT FROM AUTHOR]

Bi 0·5 Na 0·5 TiO 3 -based relaxor ferroelectric ceramics have recently gained increasing attention due to their outstanding energy storage properties. However, the trade-off between the recoverable energy storage density/efficiency and discharge rate resulted from the hysteresis of domain switching process, severely limits their applications. Herein, a strategy realizing synergistic excellent energy storage properties and fast discharge rate is proposed through regulating relaxation temperature. The relaxation temperature was decreased to below room temperature by introducing Sr 0·85 Bi 0·1 TiO 3 into Bi 0·5 Na 0·5 TiO 3 [(1- x)Bi 0·5 Na 0·5 TiO 3 - x Sr 0.85 Bi 0·1 TiO 3 , x = 0.5–0.7)], enabling the small size and weak correlation polar nanoregions (PNRs) with relatively high polarization. The trade-off was overcome by reducing the hysteresis of electrical switching of weak correlation PNRs. Thus, large recoverable energy storage density of 2.32 J/cm3 and high efficiency of 80.1% (250 kV/cm) were achieved simultaneously for x = 0.7 ceramics. Meanwhile, extremely rapid discharge rate (<30 ns) and remarkable power density of 63.7 MW/cm3, which were superior to the previously reported lead-free ceramics were realized. Besides, the 0.3BNT-0.7SBT ceramics also possess good thermal stability over 25 °C–115 °C at 100 kV/cm and good frequency stability (5–100 Hz). These properties make the 0.3BNT-0.7SBT ceramic an ideal candidate for energy storage applications. [ABSTRACT FROM AUTHOR]

An inherent conflict of (Bi 0.5 Na 0.5)TiO 3 -based (BNT) lead-free piezoelectric ceramics is the optimizing piezoelectric response (d 33) with deteriorating depolarization temperature (T d), which severely restricts the further achievements of BNT-based ceramics. A new strategy is proposed in this work to simultaneously realize high piezoelectric property (d 33 = 140 pC/N) and thermal stability (T d = 232 °C) in BNT-based ceramics by integrating layered composite structure of 0.89(Bi 0.5 Na 0.5)TiO 3 -0.11BaTiO 3 with high T d and 0.87(Bi 0.5 Na 0.5)TiO 3 -0.11BaTiO 3 -0.02(Sm 0.5 K 0.5)TiO 3 with large d 33 (BNT1/BNT2) and thermal treatment processes. In the layered composite ceramics, the composition difference induces a built-in field (E b) that promotes the diffusion of ferroelectric-relaxor (FE-RE) phase transition in the ceramics, delaying the T d to 185 °C. In addition, the thermal treatment processes facilitate both the E b expansion, stabilize the d 33 over a wide temperature range, as well as enlarge the grain size to elevate the d 33 from 133 pC/N to 145 pC/N. Hence, the strategy we proposed is promising to offer a new paradigm for designing piezoelectric materials with high piezoelectric response over a wide temperature range. [Display omitted] • An innovative solution was proposed to significantly mitigate the conflict between d 33 and T d. • BNT-based piezoceramics not only achieve large d 33 over the temperature interval of -45 ℃-244 ℃ but also improve temperature stability of d 33. • The incompatibility between d 33 and T d in bilayer structured ceramic composites at elevated temperature is resolved. [ABSTRACT FROM AUTHOR]

• A d 33 - T d trade-off was achieved in unmodified BNT-based ceramics only via optimizing the sintering temperature. • Increasing d 33 from 149 pC/N to 192 pC/N with high T d 133 °C was realized simultaneously. • The enhanced grain size and ratio of R3c/P4bm phase boost d 33 and T d. For (Bi 0.5 Na 0.5)TiO 3 -based ceramics, one of the obstacles limiting their actual application is the incompatibility of a large piezoelectric response d 33 with a low depolarization temperature T d. In this work, a high d 33 of 186 pC/N and a T d of 133 °C are achieved simultaneously in unmodified 0.93(Bi 0.5 Na 0.5) TiO 3 –0.07BaTiO 3 (BNT-7BT) ceramics only via optimizing sintering temperature. Structural and microstructural analyses show that grain size and relative content of P4bm and R3c phases in BNT-7BT ceramics can be regulated by tuning the sintering temperature (T sinter = 1100 ° C, 1120 ° C, 1140 ° C, 1160 ° C, and 1180 ° C). Thus, high sintering temperature is not only able to increase the grain size to promote the domains switching for higher the piezoelectric response, but also to enhance the ratio of R3c/P4bm phase so as to improve ferroelectric-relaxor transition temperature that defer the depolarization. Hence, the present work provides a simple and effective method for optimizing the piezoelectric properties of (Bi 0.5 Na 0.5)TiO 3 -based ceramics. [Display omitted] [ABSTRACT FROM AUTHOR]

Effect of Zn addition on microstructure, electrical properties and temperature stability and sensitivity of piezoelectric properties for 0.7Bi 1- x Zn x FeO 3 −0.3BaTiO 3 (abbreviated as BZ x F–BT) ceramics was investigated. The improved piezoelectric properties, high-temperature stability and high-temperature sensitivity by in situ and ex situ measuring were obtained by moderate Zn addition. It was demonstrated that the enhancement piezoelectric properties can be attributed to poling induced texturization degree of ferroelectric domains and increased rhombohedral structural distortions. It was proposed that the depoling temperature where the induced small signal piezoelectricity disappears stemmed from the detexturization of preferred orientation domains. The improved piezoelectric responses and high-temperature sensitivity could be attributed to the thermally activated preferred orientation domains. The good piezoelectric properties together with high-temperature stability suggest that BZ x F–BT system is a promising material for high temperature piezoelectric applications. [ABSTRACT FROM AUTHOR]

K 0.5 Na 0.5 NbO 3 (KNN)-based lead-free piezoelectric single crystals have been prepared by the Seed-Free, Solid-State Crystal Growth (SFSSCG) method, and the effects of MnO 2 doping on the structural and electrical properties were systematically investigated. The results showed that the MnO 2 -doping can promote the growth of K 0.5 Na 0.5 NbO 3 -BiAlO 3 (KNN-BA) single crystals and enhance its electrical properties. Furthermore, the size of the (1 - x)(KNN-BA)- x MnO 2 crystals reached the maximum value of about 18 × 17 × 2 mm3 at x = 0.005. Also, the color of the crystals did gradually change, from light yellow to dark brown, due to the addition of MnO 2. The XRD and refinement results showed that the addition of MnO 2 , in the range of 0 ≤ x ≤ 0.009, did not change the crystalline structure of the perovskite crystals. A two-phase perovskite crystalline structure was present in all crystals: an orthorhombic and a tetragonal phase. The content of the orthorhombic phase decreased, while the content of the tetragonal phase increased, with an increase in the MnO 2 content. In addition, the domains in the crystals were mainly composed of 180° ones and had a parallel lamellar structure. Also, the smallest average domain width was obtained for crystals with x = 0.003. These crystals had the largest piezoelectric constant of 568 pC/N and an excellent overall performance of d 33 = 568 pC/N, P r = 32.2 μC/cm2, Q m = 55.3, k t = 0.36, k p = 0.39, T C = 418 °C, ε r = 430, and tan δ = 0.015. • Compared with BiAlO 3 ceramics, single crystal exhibits more excellent electrical properties. • Using the Seed-Free, Solid-State Crystal Growth(SFSSCG) method, the process is simpler. • MnO 2 dopant promotes the growth of single crystal grains and the improvement of electrical properties. • The prepared KNN-BiAlO 3 single crystal has high piezoelectric properties. [ABSTRACT FROM AUTHOR]

Large Na0.5K0.5NbO3 ( NKN) piezoelectric single crystals were obtained by seed-free solid-state crystal growth method, which is a traditional sintering grain growth process, with LiBiO3 used as a sintering aid. The largest dimension of the single crystals obtained was 11 mm × 9 mm × 3 mm. In addition to the LiBiO3 doping content, temperature, and time effect of the crystal growth process was systematically investigated and considered from the kinetics point of view. With the assistance of Avrami analysis, parameters relevant to the crystal growth process were determined. Laue diffraction and transmission electron microscopy suggested an orthorhombic symmetry for the single crystalline structure. Dielectric-frequency-temperature measurements revealed an orthorhombic-tetragonal and tetragonal-cubic phase transition at 155°C and 405°C, respectively, both of which are typical of first-order transitions, and have a well-defined thermal hysteresis. Rayleigh analysis was performed regarding to the extrinsic reversible and nonreversible piezoelectric properties, and the result suggested a dominant intrinsic reversible piezoelectric contribution of 91.5% under E0 = 1 kV/cm AC amplitude. Such a single crystal growth process route is low cost and a relative simple preparation process. [ABSTRACT FROM AUTHOR]

One of the key challenges in the development of eco-friendly piezoceramics is to simultaneously get large piezoelectric charge coefficient d 33 and high depolarization temperature T d in a facile and effective manner. In this study, we demonstrated that built-in field E b caused by simple quenching in 0.93Bi 0.5 Na 0.5 TiO 3 -0.07BaTiO 3 piezoceramic, which promoted the T d from 140 ℃ to 184 ℃ and accompanied by the superior thermal stability of real-time d 33 (~140 ± 2.5pC/N) in a wide working temperature range of 25–170 ℃. Structural analyses illustrated that quenching induced spontaneous phase transition from tetragonal P4bm to rhombohedral R3c, which facilitated not only the development of E b but also the increase of field-induced R3c phase ratio, thereby strengthening the stability of field-induced ferroelectric state. Thus, our work validated a simple and effective method for designing high-performance piezoelectric materials with increasing T d and temperature stability without sacrificing the large piezoelectric response. [Display omitted] • • Built-in field induces spontaneous phase transition in quenched 0.93Bi 0.5 Na 0.5 TiO 3 -0.07BaTiO 3 ceramic. • • The depolarization temperature T d increases from 140 ℃ to 184 ℃ after quenching. • • Attaining the temperature-independent d 33 (~140pC/N) in a wide working temperature range of 25–170 ℃. [ABSTRACT FROM AUTHOR]

• The semiconductive (K 0.5 Na 0.5)NbO 3 ceramics were obtained by introducing Ca(Ni 0.5 Nb 0.5)O 3-δ component with low valent Ni. • The semiconduction method of KNN-based ferroelectric ceramics and its relationship with photo-dielectric response are studied. • A dielectric tunability of up to 387% under ultraviolet light irradiation was obtained. • The switching behavior of ceramics was also studied. The lead-free ferroelectric ceramics with high photo-dielectric response will contribute to developing new contactless photoelectric devices. The (1- x)(K 0.5 Na 0.5)NbO 3 - x Ca(Ni 0.5 Nb 0.5)O 3-δ (KNN- x CNN) ferroelectric semiconductive ceramics prepared by solid-phase sintering were used to investigate photo-dielectric behavior. After introducing the CNN component, the hysteresis loops of KNN- x CNN ceramics changed from the normal P - E loops to the pinched P - E loops, and the relaxation behavior was enhanced by the increase of diffusion coefficient from 1.16 to 1.85. The phase structure transformed from the orthogonal phase to the tetragonal phase. The grain size decreasing from 360 nm to 170 nm was refined. The bandgap decreased significantly from 2.29 eV to 1.40 eV. An obvious enhanced photo-dielectric response was achieved under ultraviolet light irradiation, which shows high dielectric tunability of ~387% at x = 0.015. Meanwhile, the switching behavior was analyzed by the capacitive ratio under light on and off state, which is about 5. These results pave the way for new photoelectric coupling devices such as photo-adjustable capacitor and capacitive switching. [ABSTRACT FROM AUTHOR]

• Dielectric/ferroelectric properties of BANT-xBNN ceramics were investigated. • Perfect ferroelectricity and low optical band gap ~2.3 eV. • The improved J sc and V oc , poled at 2.0 kV, is 2.79 nA/cm2 and 0.54 V, respectively. Perovskite-oxide ferroelectric semiconductors were widely concerned in photovoltaic applications due to its excellent optical absorption and thermal stability. In this work, Ba x Bi 0.5-0.5 x Ag 0.05-0.5 x Na 0.45 Ti 1- x Ni 0.5 x Nb 0.5 x O 3 ceramics (abbreviation as BANT- x BNN) were successfully prepared by using a solid-state reaction method. All the ceramics illustrate perfect ferroelectric behavior. The addition of BaNi 0.5 Nb 0.5 O 3 can substantially reduce the band gap of Ag doped Bi 0.5 Na 0.5 TiO 3 material to ~2.3 eV. The short-circuit current (J sc) and the open-circuit voltaic (V oc) of the selected BANT-0.04BNN ceramic poled at 2.0 kV, is 2.79 nA/cm2 and 0.54 V, respectively. The novel BANT- x BNN system has broad application prospects for ferroelectric photovoltaic devices. [ABSTRACT FROM AUTHOR]