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Mn‐doped (1‐x)Bi0.5(Na0.8K0.2)0.5TiO3‐xBiAlO3 (Mn:BNKT‐xBA) thin films were synthesized on lanthanum nickelate‐coated silicon substrates by sol‐gel method. The second phase issue of the film can be effectively addressed by optimizing the substrate, and the maximum polarization and breakdown strength can be increased by introducing the proper amount of Al3+, which is advantageous for the film for energy storage. The results have shown that the Mn:BNKT‐0.03BA film exhibits superior ferroelectric properties (with remanent polarization (Pr) of 23.72 µC/cm2, maximum polarization (Pmax) of 75.37 µC/cm2), which could be an excellent candidate for ferroelectric thin film capacitors. [ABSTRACT FROM AUTHOR]

With the gradual promotion of new energy technologies, there is a growing demand for capacitors with high energy storage density, high operating temperature, high operating voltage, and good temperature stability. In recent years, researchers have been devoted to improving the energy storage properties of lead‐based, titanium‐based, and iron‐based multilayer ceramic capacitors (MLCCs). However, limited research has been conducted into MLCC development using NaNbO3 (NN)‐based materials. In this paper, the successful achievement of excellent overall energy storage performance in a novel NaNbO3–(Bi0.5Na0.5)TiO3–Bi(Mg0.5Hf0.5)O3 lead‐free MLCCs is presented. The disordered tilting around the cp axis, disrupts Na and Bi ions' long‐range displacements and induces PNRs and strong relaxor behavior, which ensures a superior energy storage performance, together with the multilayer ceramic design strategy. As a result, the NN‐based MLCC device presents an ultra‐high Wrec = 12.65 J cm−3 and η = 88.5%, simultaneously showing superior temperature stability (Wrec varies <±1% and η varies <±6% from −50 to 125 °C) and fatigue resistance (Wrec and η vary <±1% over 107 cycles). This study highlights the advanced energy storage potential of NaNbO3‐based MLCCs for various applications, and ushers in a new era for designing high‐performance lead‐free capacitors that can operate in harsh environments. [ABSTRACT FROM AUTHOR]

Bismuth layer structured ferroelectrics (BLSFs) have drawn much attention due to their great potential for high‐temperature applications. It is generally accepted that BLSFs with small orthorhombic distortion should have low TC. In this paper, we report an anomalous example Li0.5Bi2.5Nb2O9 (LBN), which has small orthorhombic distortion but very high TC. LBN shows the highest TC (834°C) among currently reported prototype alkali‐metal BLSFs, which is attributed to its small tolerance factor. However, the refinement result reveals that LBN is orthorhombic with the space group of A21am, and the orthorhombic distortion of LBN a/b is merely 1.0019. The measurement of piezoelectric coefficient (d33 ∼ 6 pC/N) and observation of striped domain structure confirm the ferroelectricity nature of LBN. This work deepens our understanding of BLSFs and may lead to the finding of more novel BLSFs with high performance. [ABSTRACT FROM AUTHOR]

The pressure‐driven explosive energy‐conversion (EEC) effect of ferroelectric (FE) materials has been extensively studied in scientific research and high‐tech applications owing to its high pulse‐power output capability. The fundamental principle of this effect is pressure‐driven phase transition and depolarization in FE materials, accompanied by discharging behavior from the charge release upon pressure loading. Pb(Zr,Ti)O3 has been an excellent example of a materials exhibiting these properties. However, recent investigations have been focused on developing other lead‐based or lead‐free materials with a higher energy‐storage ability and better temperature stability. In this article, we review the recent progress achieved in the past decades on different types of lead‐based and lead‐free ceramics, single crystals, and multilayer films, based on their unique pressure‐driven phase transition and energy‐conversion properties. Their pulse power discharging performance under actual shock‐wave compression is also summarized, followed by a detailed discussion of the failure mechanism under shock‐wave compression. Finally, several issues and perspectives are proposed for future investigation in this area. All these not only assist in the design of new materials for high‐performance EEC but are also helpful for the practical application of these promising materials in pulse‐power technologies. [ABSTRACT FROM AUTHOR]

The most promising candidates for energy storage capacitor application are relaxor ferroelectrics, among which, the perovskite structure ferroelectric ceramics have witnessed great development progress. However, less attention has been paid on tetragonal tungsten bronze structure (TTBS) ceramics because of their lower breakdown strength and polarization. Herein, a multiscale regulation strategy is proposed to tune the energy storage performances (ESP) of TTBS ceramics from grain, domain, and macroscopic scale. The enhanced relaxor behavior with dynamic polar nanodomains guarantees low remanent polarization, while the refined grains and enlarged bandgap ensure increased breakdown strength. Hence, excellent ESP is realized in unfilled TTBS Sr0.425La0.1□0.05Ba0.425Nb1.4Ta0.6O6 (SLBNT) ceramics with an ultrahigh recoverable energy density of 5.895 J cm−3 and a high efficiency of 85.37%. This achievement notably surpasses previous studies in TTBS ceramics and is comparable to that of perovskite components. Meanwhile, the energy density exhibits a wide temperature, frequency, and cycling fatigue stability. In addition, high power density (257.89 MW cm−3), especially the ultrafast discharge time (t0.9 = 16.4 ns) are achieved. The multiscale regulation strategy unlocks the energy storage potential of TTBS ceramics and thus highlights TTBS ceramics as promising candidates for energy storage, like perovskite structured ceramics. [ABSTRACT FROM AUTHOR]

Bi0.5Na0.5TiO3‐based ceramics with high remnant polarization Pr have shown outstanding potential in the application of high‐power ferroelectric transducers. However, low depolarization temperature Td is an obstacle for their application. Here, a composition design strategy was proposed to simultaneously improve the Td and Pr in BNT‐based materials. Ultrahigh Pr of 40.56 µC/cm2 and relative high Td of 184°C were synergistically achieved in (Bi0.5Na0.5)(Ti0.995Mn0.005)O3 (BNMT) ceramics by adding 1.0 mol% BiGaO3 (BG), which is superior to other reported lead‐free systems. The excellent ferroelectric properties were attributed to strengthen ferroelectric order as evidenced by increased rhombohedral distortion. Meanwhile, the enhanced depolarization temperature, increasing from 168°C for x = 0% to 184°C for x = 1.0%, can be ascribed to the suppression of the thermal‐induced ferroelectric‐relaxor phase transition by adding BG. Those results enable the BNMT‐BG systems ceramics to be an attractive candidate for application in high‐power supplies. [ABSTRACT FROM AUTHOR]

(Pb, La)(Zr, Ti)O3 antiferroelectric (AFE) materials are promising materials due to their energy‐storage density higher than 10 J cm−3, but their low energy‐storage efficiency and poor temperature stability limit their application. In this paper, the (1 − x)(Pb0.9175La0.055)(Zr0.975Ti0.025)O3–xPb(Yb1/2Nb1/2)O3 (PLZTYN100x) AFE ceramics were prepared via two‐step sintering method and investigated thoroughly. With the doping of Yb3+ and Nb5+, the phase structure transforms from the orthorhombic phase (AFEO) to the coexistence of the orthorhombic‐and‐tetragonal phases. This structure reduces the free energy difference between the AFE and ferroelectric phases and reduces the fluctuation of energy with temperature, improving the energy storage efficiency and temperature stability. When the x = 0.05 (PLZTYN5), the AFE ceramic exhibits excellent temperature stability and ultrahigh energy storage performance, whose recoverable energy density (Wrec) is 6.8–8.2 J cm−3 at 30 kV mm−1 in the temperature range from −55 to 75°C, and efficiency (ƞ) is 78%–86.7%. In addition, the change of Wrec is less than 15%, exceeding the performance of most AFE ceramics. The results demonstrate that the PLZTYN5 ceramic has great potential in pulse power capacitors. [ABSTRACT FROM AUTHOR]

The energy storage performance of antiferroelectric ceramic capacitors has always gain much attention. Hysteresis, transition field, and polarization intensity are crucial factors influencing energy storage performance. A‐site doped small radius ions have been shown in numerous investigations to enhance the switching field, minimize hysteresis, but decrease maximum polarization intensity. How to maintain the high polarization while optimizing other parameters is a great challenge, and this problem has received scant attention in the research literature to date. In this work, Pb1‐xSrx(Zr0.54Sn0.46)0.975Nb0.02O3 (x = 0, 0.02, 0.06, 0.08, 0.1, 0.12, 0.14, 0.16, 0.20) antiferroelectric ceramics show high polarization stability. When the Sr2+ content is within 12 mol%, the saturation polarization intensity always remains at a large value (> 44μC/cm2), and the rate of change is as low as 6%. Pb0.92Sr0.08(Zr0.54Sn0.46)0.975Nb0.02O3 also displays great polarization temperature stability with a minimal change rate of 8.5% in a wide temperature range from ‐55 to 85°C. Additionally, this ceramic also has a superior energy storage performance that the recoverable energy density and energy storage efficiency and 8.95 J/cm3 and 80.4%, respectively. This work paves the way for practical simultaneous polarization and other parameter optimization. [ABSTRACT FROM AUTHOR]

The recently discovered ductile/plastic inorganic semiconductors pave a new avenue toward flexible thermoelectrics. However, the power factors of current ductile/plastic inorganic semiconductors are usually low (below 5 µW cm−1 K−2) as compared with classic brittle inorganic thermoelectric materials, which greatly limit the electrical output power for flexible thermoelectrics. Here, large plasticity and high power factor in bulk two‐dimensional van der Waals (2D vdW) single‐crystalline SnSe2 are reported. SnSe2 crystals exhibit large plastic strains at room temperature and they can be morphed into various shapes without cracking, which is well captured by the inherent large deformability factor. As a semiconductor, the electrical transport properties of SnSe2 can be readily tuned in a wide range by doping a tiny amount of halogen elements. A high power factor of 10.8 µW cm−1 K−2 at 375 K along the in‐plane direction is achieved in plastic single‐crystalline Br‐doped SnSe2, which is the highest value among the reported flexible inorganic and organic thermoelectric materials. Combining the good plasticity, excellent power factors, as well as low‐cost and nontoxic elements, bulk 2D vdW single‐crystalline SnSe2 shows great promise to achieve high power density for flexible thermoelectrics. [ABSTRACT FROM AUTHOR]

The pressure‐driven force‐electric conversion materials with extremely rapid response time have been widely used in mining, defense, and energy areas. The discharge process by the force‐electric conversion effect in ferroelectrics is dominated by polar‐nonpolar phase transformation. In this work, (Pb0.985La0.01)(ZrxTi1‐x)O3 (PLZT, x = 0.85–0.94) ceramics is designed by tunning Zr4+/Ti4+ ratio and aliovalent La doping to achieve high remnant polarization (Pr) and excellent temperature stability. We focus on the pressure‐driven depolarization in PLZT ceramics, and their corresponding phase structure, ferroelectric properties, dielectric properties, and thermal depolarization. In PLZT (x = 0.93) ceramics, the original polarization P0 increases to 43.42 μC/cm2. The pressure‐driven depolarization releases 37.66 μC/cm2 with the depolarization proportion of 86.73%, which is attributed to irreversible ferroelectric‐antiferroelectric phase transition. It also exhibits excellent temperature stability up to 120°C (> 36 μC/cm2). This work provides a high‐performance alternative to Pb(Zr0.95Ti0.05)O3 and guidance for the development of pulse power energy conversion devices. [ABSTRACT FROM AUTHOR]

Pb0.99(Zr0.95Ti0.05)0.98Nb0.02O3 ferroelectric ceramics with porous structure of periodic distribution were fabricated successfully via Direct Ink Writing, a type of 3D printing technique. The effect of periodically distributed porous microstructure on the dielectric, ferroelectric, as well as hydrostatic‐pressure‐induced depolarization properties of PZT95/5 ferroelectric ceramics, was investigated. The printed porous ceramics exhibit relatively good viscoelasticity to retain the periodic structure during 3D printing and drying. In contrast with dense PZT95/5 ferroelectric ceramics prepared by conventional solid‐state sintering, low bulk density of the periodically distributed porous PZT95/5 ceramics leads to a decreased remanent polarization of 22.9 µC/cm2 under 2 kV/mm. As the hydrostatic pressure increased, the poled periodically distributed porous PZT95/5 ceramics depolarize sharply under a low and narrow hydrostatic pressure range of 113–116 MPa with a released charge density of 23.9 µC/cm2, while the poled dense PZT95/5 ceramics depolarize under a range of 250–278 MPa. Therefore, the introduction of periodically distributed micropores into PZT95/5 ceramics decreases the ferroelectric‐to‐antiferroelectric phase transition hydrostatic pressure significantly and maintained relatively excellent other properties simultaneously, such as temperature stability and low dielectric loss. The almost sharp depolarization behavior under a significantly decreased hydrostatic pressure demonstrates that periodically distributed porous PZT95/5 ferroelectric ceramics fabricated controllably by 3D printing exhibit excellent performances and prospects in mechanical–electrical energy conversion applications. [ABSTRACT FROM AUTHOR]

(Bi0.5Na0.5)TiO3 (BNT)‐based ferroelectric ceramics have drawn extensive attention because of their excellent electrical properties and interesting depolarization behavior. However, the poor thermal stability of electrical properties limits their practical application. In this work, the effect of sintering temperature (Ts) on the depolarization behavior of BNT‐based ceramics was systematically investigated. It is found that the depolarization temperature Td determined from pyroelectric measurement tends to decrease with increasing Ts, which indicates that lower Ts defers the ferroelectric‐relaxor (FE‐RE) phase transition. However, for the samples sintered at higher Ts (such as 1180°C), although the Td is reduced, the thermal stability is better compared with the sample sintered at lower Ts (1100°C) because the diffuse behavior of the FE‐RE phase transition is suppressed. According to these results, we propose that the thermal stability of electrical properties for BNT‐based ceramics is not only related to high Td, but also to the diffuse degree of phase transition. [ABSTRACT FROM AUTHOR]

Pulse power energy conversion materials with ultrafast discharge processes and ultrahigh power densities have been widely used in the defense, energy, medical, and mining fields. The pressure‐driven depolarization in ferroelectric materials is significant and accounts for the discharge processes. In this study, we focus on pressure‐induced depolarization in (Pb1‐1.5xLax)(Zr0.80Ti0.20)O3 (PLZT) (x = 0‐0.07) ceramics, and their corresponding phase structure, dielectric properties, ferroelectric properties, and thermal depolarization performances. Although a satisfactory pulse power energy conversion performance has been achieved in Pb(Zr0.95Ti0.05)O3 materials, poor temperature stability negatively influences their application. The static charge densities of PLZT (x = 0.04, 0.06) decreased from 29.11 μC/cm2 and 31.53 μC/cm2 to 19.76 μC/cm2 and 6.56 μC/cm2 under 400 MPa hydrostatic pressure, respectively, which is attributed to a pressure‐driven ferroelectric‐antiferroelectric phase structural transition. In particular, the temperature stability of PLZT (x = 0.06) materials is up to 87°C. This study may guide the further development pulse power energy conversion devices. [ABSTRACT FROM AUTHOR]

Ceramic‐based dielectric capacitor are highly suitable for pulsed power applications due to their high power density and excellent reliability. However, the ultrahigh applied electric field limit their applications in integrated electronic devices. In this work, (1−x){0.96(Bi0.5Na0.5)(Ti0.995Mn0.005)O3‐0.04BiAlO3}‐xNaNbO3 (BNT‐BA‐xNN, x = 0, 0.04, 0.08, 0.12, and 0.16) ternary ceramics were designed to achieve excellent energy storage properties. It was found that the introduction of NaNbO3 (NN) effectively increase the difference (ΔP) between Pmax and Pr, resulting in an obvious enhancement of the energy storage properties. High recoverable energy storage density, responsivity, and power density, that is, Wrec = 2.01 J/cm3, ξ = Wrec/E = 130.69 J/(kV⋅m2), and PD = 25.59 MW/cm3, accompanied with superior temperature stability were realized at x = 0.14 composition. In addition, the thermal stable dielectric properties of the sample can be prominently improved with increasing NN content. The temperature coefficient of capacitance (TCC) of x = 0.16 composition is lower than 15% over the temperature range from 49°C to 340°C, with a high dielectric permittivity of 1647 and a low dielectric loss (0.0107) at 150°C. All these features show that the BNT‐BA‐xNN ceramics are promising materials for energy storage application. [ABSTRACT FROM AUTHOR]

Ferroelectric materials under shock compression can generate current and power by a drastic change of the remnant polarizations and surface bound charge. This behavior has been employed in applications involving nuclear fusion trigger, energy storage devices, and high pulse power sources. Despite the large power output in lead‐containing ferroelectrics, lead‐free materials are highly desirable owing to the environmental concerns. Herein, the phase transition behaviors and current outputs of 0.92Bi0.5Na0.5TiO3‐0.08BiAlO3 (BNT‐8BA) materials are studied under high pressure. The BNT‐8BA ferroelectric ceramics can be completely depolarized from polar to the nonpolar state under shock compression, resulting in a current output in the external circuit. The phase‐transition‐induced depolarization pressures of BNT‐8BA are lower than those of the pure Bi0.5Na0.5TiO3 under both dynamic and static high‐pressure loads. These results can allow the understanding of the high‐pressure behavior of BNT‐8BA for application as ferroelectric pulsed power supply. [ABSTRACT FROM AUTHOR]

A magnetoelectric (ME) heterostructure was fabricated by depositing a Ni‐Mn‐Ga (NMG) magnetic film on an antiferroelectric (AFE) PLZST—(Pb, La)(Zr, Sn, Ti)O3—ceramic substrate. Significant and reversible electric field‐induced relative magnetization changes (∆M/M0) were firstly observed in this magnetic/AFE heterostructure, and the ∆M/M0 vs electric field loops have been found to correspond well with the strain‐electric field curve of PLZST ceramic. The maximum ∆M/M0 variation can reach 15%, indicating an obvious strain‐mediated converse magnetoelectric (CME) effect. A maximum CME coefficient of 1.14 × 10‐9 s/m was obtained at the switching electric fields of PLZST. The collected results suggest that AFE materials with a large electric‐field‐induced phase transition strain could be alternative candidates in ME coupling heterostructures. [ABSTRACT FROM AUTHOR]

Solid solutions of (1−x)PbZrO3‐xBa(Mg1/3Nb2/3)O3 (PZ‐xBMN, x = 0.02, 0.03, 0.04, and 0.05) were prepared, and their microstructures, electrical properties, and phase transition behaviors under hydrostatic pressure were investigated. It was found that the incorporation of BMN into PZ can provide improved ferroelectric properties, leading to the formation of antiferroelectric/ferroelectric phase boundaries in PZ‐xBMN ceramics when the value of x is between 0.02 and 0.03. It was also demonstrated that the ferroelectric phases exhibit excellent temperature stability in the remanent polarization. Importantly, complete depolarization was observed in the PZ‐xBMN solid solution due to the hydrostatic pressure‐induced ferroelectric‐antiferroelectric phase transition. The resultant properties and phase transition behaviors of PZ‐xBMN ceramics under pressure will benefit their application in pulsed power supplies. [ABSTRACT FROM AUTHOR]

In this work, the effects of composition, temperature, and poling on the phase transition behavior under hydrostatic pressure of lead‐free (1‐x)[(0.98Bi0.5Na0.5Ti0.995Mn0.005O3‐0.02BiAlO3)]‐xNaNbO3 (BNT‐BA‐xNN) ceramics were investigated. It was found that hydrostatic pressure can induce a phase transformation from ferroelectric (FE) to relaxor (RE). Meanwhile, the FE‐RE phase transition pressure (PFR) tends to decrease as the NN addition increases. Moreover, increasing temperature exhibits a similar effect that is, reducing PFR. The reduced PFR were considered to result from the reduced FE stability and increasing proportion of RE phase. However, PFR was obviously enhanced after poling, which can be attributed to the induced FE phase and the formation of macrodomains with application of an electric field. These results will aid in understanding the phase transition behavior of BNT‐based relaxor ferroelectrics for applications under hydrostatic pressure. [ABSTRACT FROM AUTHOR]

Abstract: (1−x)Bi1/2Na1/2TiO3‐xPbMg1/3Nb2/3O3[(1−x)BNT‐xPMN] ceramics have been fabricated via a conventional solid‐state method for compositions x ≤ 0.3. The microstructure, phase structure, ferroelectric, and dielectric properties of ceramics were systematically studied as high‐temperature capacitor materials. XRD pattern certified perovskite phase with no secondary phase in all compositions. As PMN concentration increased, the phase of (1−x)BNT‐xPMN ceramics transformed from ferroelectric to relaxor gradually at room temperature, with prominent enhancement of dielectric temperature stability. For the composition x = 0.2, the temperature coefficient of capacitance (TCC) was <15% in a wide temperature range from 56 to 350°C with high relative permittivity (>3300) and low dielectric loss (<0.02) at 150°C, which indicated promising future for (1−x)BNT‐xPMN system as high‐temperature stable capacitor materials. [ABSTRACT FROM AUTHOR]

Abstract: High pyroelectric performance and good thermal stability of pyroelectric materials are desirable for the application of infrared thermal detectors. In this work, enhanced pyroelectric properties were achieved in a new ternary (1−x)(0.98(Bi0.5Na0.5)(Ti0.995Mn0.005)O3–0.02BiAlO3)–xNaNbO3 (BNT–BA–xNN) lead‐free ceramics. The effect of NN addition on the microstructure, phase transition, ferroelectric, and pyroelectric properties of BNT–BA–xNN ceramics were investigated. It was found that the average grain size decreased as x increased to 0.03, whereas increased with further NN addition. The pyroelectric coefficient p at room temperature (RT) was significantly increased from 3.87 × 10−8Ccm−2K−1 at x = 0 to 8.45 × 10−8Ccm−2K−1 at x = 0.03. The figures of merit (FOMs), Fi, Fv and Fd, were also enhanced with addition of NN. Because of high p (7.48 × 10−8Ccm−2K−1) as well as relatively low dielectric permittivity (~370) and low dielectric loss (~0.011), the optimal FOMs at RT were obtained at x = 0.02 with Fi = 2.66 × 10−10 m/V, Fv = 8.07 × 10−2 m2/C, and Fd = 4.22 × 10−5 Pa−1/2, which are superior to other reported lead‐free ceramics. Furthermore, the compositions with x ≤ 0.03 exhibited excellent temperature stability in a wide temperature range from 20 to 80°C because of high depolarization temperature (≥110°C). Those results unveil the potential of BNT–BA–xNN ceramics for infrared detector applications. [ABSTRACT FROM AUTHOR]

Abstract: The effect of lanthanum (La) content on the phase transformation of Pb1−3x/2Lax(Zr0.42Sn0.40Ti0.18)O3 (PLZST 100x/42/40/18, 0 ≤ x ≤ 0.06) ceramics was investigated by the dielectric and ferroelectric properties. The base composition PLZST 0/42/40/18 located in the ferroelectric (FE) rhombohedral phase region. As x increased, the compositions showed successively FE and antiferroelectric (AFE) state at room temperature, and their peak temperatures (Tmax) decreased gradually in line as Tmax = 162.21‐1507x. Evidence was presented that there were two dielectric anomalies in PLZST 2/42/40/18, which were corresponding to the FE‐AFE and AFE‐paraelectric (PE) phase transformations, respectively. With increasing the dc bias fields, the two phases merged into one. PLZST 3/42/40/18 showed AFE characteristics with the first loop outside of the second loop and there was only one dielectric inflection. The critical lanthanum content occurred at x = 0.03 from the dielectric temperature spectra and hysteresis loops. Furthermore increase in La above 0.03, these compositions showed typical antiferroelectric behaviors with double hysteresis loops. The stored energy properties of the three compositions (PLZST 4/42/40/18, 5/42/40/18 and 6/42/40/18) displayed different temperature dependencies from room temperature to 140°C (over their respective Tmax). Comparing the above results with previous investigations on PLZSTs, some questions were discussed. [ABSTRACT FROM AUTHOR]

Abstract: Energy storage materials and their applications have long been areas of intense research interest for both the academic and industry communities. Dielectric capacitors using antiferroelectric materials are capable of displaying higher energy densities as well as higher power/charge release densities by comparison with their ferroelectric and linear dielectric counterparts and therefore have greater potential for practical energy storage applications. Over the past decade, extensive efforts have been devoted to the development of high performance, antiferroelectric, energy storage ceramics and much progress has been achieved. In this review, the current state‐of‐the‐art as regards antiferroelectric ceramic systems, including PbZrO3‐based, AgNbO3‐based, and (Bi,Na)TiO3‐based systems, are comprehensively summarized with regards to their energy storage performance. Strategies are then discussed for the further improvement of the energy storage properties of these antiferroelectric ceramic systems. This is followed by a review of the low temperature sintering techniques and the charge–discharge performance of antiferroelectric ceramics from a practical point of view. The review will be of benefit for researchers in the area as it offers a quick overview of recent progress in the development of various kinds of antiferroelectric ceramics and their properties. It should also stimulate the development of novel antiferroelectric ceramics with high energy storage performance. [ABSTRACT FROM AUTHOR]

Electrocaloric response in slim‐like (Ba0.9Ca0.1)(Zr0.2Ti0.8)O3 and square‐like Pb(Zr0.95Ti0.05)O3 hysteresis loops are observed by cycling samples between positive and negative values of electric field, respectively. The slim‐like (Ba0.9Ca0.1)(Zr0.2Ti0.8)O3 ceramics represent a typical electrocaloric response, while the square‐like Pb(Zr0.95Ti0.05)O3 ceramics depict an unusual electrocaloric response. It is worth noting that the unusual electrocaloric response (inverse electrocaloric effect) can be induced by inverse electric field. Furthermore, the highest value of inverse electrocaloric effect is not obtained at negative coercive field but at values that are half of it. With the increase in inverse electric field, the value of induced unusual electrocaloric effect becomes weaker and only positive electrocaloric response is present at higher magnitudes of inverse field. In the present work, the relationship between electrocaloric response and polarization behavior of these two kinds of samples are discussed. [ABSTRACT FROM AUTHOR]

In this paper, the influence of phase evolution on polarization change and electrocaloric response in lead-free (Ba0.9Ca0.1)(Ti1− x Zr x)O3 ceramics ( BCTZ) was systematically investigated. With increasing Zr/Ti ratio, the phase structure and phase transition behavior were greatly changed, resulting in various temperature and electric field dependence of electrocaloric responses. For x=0.05, a peak electrocaloric temperature change 1.64 K (at 130°C) and corresponding entropy change 1.78 J·kg−1·K−1 were obtained for 0-7 kV·mm−1 electric field. Negative electrocaloric temperature change in −0.1 K was obtained below Curie temperature ( Tc), which may be induced by the orthorhombic-tetragonal ferroelectric phase transition. With the increase in x, the peak value of the electrocaloric response decreased but much better temperature stability was observed. Simultaneously the negative electrocaloric response gradually disappeared with the disappearance of the low temperature ferroelectric-ferroelectric phase transition. For x=0.2, electrocaloric response showed good temperature stability ranging from room temperature to 130°C, attributing to the relaxor ferroelectric feature. [ABSTRACT FROM AUTHOR]

PZT95/5 ferroelectric ceramics are widely utilized in pulsed power devices and the remanent polarization Pr of poled PZT95/5 can characterize the shock-driven energy density. However, this remanent polarization is difficult to be measured nondestructively. In this article, a series of pyroelectric tests of poled PZT95/5 ceramics were conducted near room temperature, from 25°C to 20°C. A linear relation between Pr and pyroelectric coefficient p was found, that is, Pr=1190.5( K)× p, which provides an effective way to nondestructively estimate the value of Pr of the poled PZT95/5 ceramics by measuring the pyroelectric coefficient p at room temperature. According to Devonshire's phenomenological theory, this result could be explained by a modified equation: [ABSTRACT FROM AUTHOR]

The electrical hysteresis behaviors and energy storage performance of Pb0.97La0.02(Zr0.58Sn0.335Ti0.085)O3 antiferroelectric ( AFE) ceramics were studied under the combined effects of electric field and temperature. It was observed that the temperature dependence of recoverable energy density ( Wre) of AFE ceramics depends critically on the applied electric field. While Wre at lower electric fields (<8 kV/mm) shows increasing tendency with increasing temperature from 20°C to 100°C, Wre at higher electric fields (>8 kV/mm) demonstrates decreasing dependence. There exists an appropriate electric field (8 kV/mm) under which the AFE ceramics exhibit nearly temperature-independent Wre (the variation is less than 0.5% per 10°C). The underlying physical principles were also discussed in this study. These results indicate that the temperature dependence of Wre of AFE materials can be tuned through selecting appropriate electric fields and provide an avenue to obtain thermal stable energy storage capacitors, which should be of great interest to modern energy storage community. [ABSTRACT FROM AUTHOR]

Flat and wrinkled La0.7Sr0.3MnO3 ( LSMO) thin films were prepared by sol-gel method, respectively, on Si (001) substrates by adjusting heating rate at drying stage. Wrinkled film has larger grains than flat film. Coercive field (about 27 Oe) of wrinkled film is higher than that of flat film, which is much low as around 5 Oe. Compared with flat films, wrinkled films have larger magnetization, higher Curie temperature (334 K) and peak resistivity temperature (243 K), and lower resistivity (0.18 Ohm·cm at 300 K). The introducing of wrinkles is an efficient way to induce compressive stress in sol-gel derived polycrystalline LSMO films and enhance the magnetic and electric properties. [ABSTRACT FROM AUTHOR]

(Bi0.5Na0.5)TiO3-BiAlO3 lead-free materials exhibit excellent ferroelectric properties, but its depolarization temperature is relatively low which is the major obstacle limiting the material's practical application. In this study, the effects of Manganese (Mn) modification on the microstructure, ferroelectric properties and depolarization behavior of 0.96(Bi0.5Na0.5)(Ti1− xMn x)O3-0.04BiAlO3 ceramics were investigated. It was found that the average grain size was enlarged and ferroelectric properties were enhanced with small Mn addition, meanwhile the tangent loss decreased. The remnant polarization ( Pr) of the samples reached an optimal value (~41 μC/cm2) as Mn content increased up to 0.7 mol%, whereas further addition resulted in the decrease in Pr. Moreover, appropriate Mn addition ( x=0.7%) can improve the depolarization temperature from 140°C to 161°C determined from thermally stimulated depolarization currents measurement. [ABSTRACT FROM AUTHOR]

Lattice dynamics and phase transitions of Aurivillius ferroelectric Bi3Ti1 - xWxNbO9+δ (BTWN100x, 0 ≤ x ≤ 15%) ceramics have been investigated by temperature-dependent Raman spectra (80-800 K) and far-infrared (FIR) reflectance spectra (6-300 K). The frequency, intensity, and line width of phonon modes as well as complex dielectric functions of BTWN100x ceramics have been extracted by fitting Raman and FIR reflectance spectra with the multi-Lorentzian oscillator model. It was found that the dielectric constants at a certain frequency region become lower with increasing W compositions at room temperature due to the compressive stress onW-O bands. Moreover, the temperature- dependent behavior of optical phonon modes in BTWN100x ceramics indicates that there are two intermediate phases during the phase transition from paraelectric I4/mmm to ferroelectric A21am phase on cooling. The phase diagram of BTWN100x ceramics as a function ofWcomposition has been improved. [ABSTRACT FROM AUTHOR]

High-quality Yttrium iron garnet (YIG) films with crack-free surface and improved magnetic performance were grown on platinum (Pt)-buffered Si substrates by chemical solution deposition technique. The saturation magnetization of obtained YIG films can reach 124 emu/cm³, which was the 88% theoretical value of YIG single crystal. The effects of annealing condition were also discussed. When annealed at 750°C for 1 h, YIG films showed a very small coercive field of 12 Oe and the peak-to-peak ferromagnetic resonance linewidth can be as low as 95 Oe at 9.10 GHz. The results demonstrated that YIG films prepared on Pt-buffered Si substrates can be beneficial to the application of YIG films to integrated devices. [ABSTRACT FROM AUTHOR]

The dynamic hysteresis scaling behaviors of Nb-doped Pb(Zr0.52Ti0.48)O3 ceramics have been investigated as a function of electric field amplitude ( E0) and frequency ( f) at different temperatures ( T). The loop area of saturated loops is found to follow various power laws as ∝ E00.3065 at fixed f and ∝ f 0.0120 at fixed E0. Furthermore, the linear scaling relation = k3 fα E0β + b3 is estimated under various temperatures. The exponents α (=0.01) and β (=0.10) are T-independent, whereas the slopes k3 and y-intercepts b3 are T-dependent because the increasing temperature in the same phase range only decreases the threshold field of the reversal rather than change the dynamic reversal process. [ABSTRACT FROM AUTHOR]

Ba0.63Sr0.37TiO3 (BST) films were first deposited on SiC substrates with LNO bottom electrodes by magnetron sputtering. The BST/LNO/SiC thin films exhibit high dielectric tunability and low dielectric loss while maintaining excellent temperature coefficient of dielectric constant in the temperature range between 250 and 350 K. We also investigated the effect of film thickness on the dielectric properties. BST(430 nm)/LNO/SiC film has higher tunability (68.09% @700 kV/cm), lower loss tangent (tanδ = 0.00987) and quite a bit higher figure of merit (FOM = 68.99) as compared with that of BST(300 nm)/LNO/SiC film. Our results demonstrate that combining ferroelectric BST films with SiC substrates is very promising for the development of tunable devices over a large temperature range. [ABSTRACT FROM AUTHOR]

Dynamic hysteresis of Nb-doped Pb( Zr1− x Ti x) O3 ( PZT, 0.20 ≤ x ≤ 0.60) ceramics were studied systemically at different field ( E) and frequency ( f). The hysteresis loops were strongly dependent on E and f. The measured coercive fields ( Ec0) were far lower than the calculated values based on the Landau-Ginzburg theory, and increased dramatically from the rhombohedral phase to the tetragonal phase while had less variation with composition in the same phase. With increasing E or f for each composition, three types of loops were observed: linear, minor, and saturated loops. The cross fields ( E0), cross polarizations ( P0), and hysteresis areas ( ) showed different variation regularities with f. Similar varying curves were observed for all PZT ceramic samples by normalizing E0, P0, and with E/Ec0, which indicated the same polarization switching for different domain structures. Further analyses revealed that the switching processes can be divided into three stages: space charge polarization, domain switching, and steady state. The first and second stage occurred at ~0.5 and ~1.5 E/ Ec0, respectively. These results would be very helpful to further understand the polarization switching of ferroelectric ceramics. [ABSTRACT FROM AUTHOR]

The low-temperature sintering and electric properties of Pb0.99( Zr0.95 Ti0.05)0.98 Nb0.02 O3 ( PZTN 95/5) ferroelectric ceramics with CuO addition was investigated. The CuO addition significantly promoted the densification and reduced the sintering temperature of PZTN 95/5 ceramics by more than 200°C. The 0.2 wt% CuO-added sample sintered at 1150°C exhibited the optimum relative density of 96.7% and excellent electric properties with values of Pr = 37.80 μC/cm2, TC = 223°C, εr = 329, and tan δ = 0.016, which were superior to that of PZTN 95/5 ceramics sintered at 1350°C. [ABSTRACT FROM AUTHOR]

Temperature-dependent ferroelectric dynamic hysteresis properties of modified Pb(Mg1/3Nb2/3)O3-Pb(Zr,Ti)O3 (PMN-PZT) ceramics have been investigated in a wide range from 298 to 433 K. Interestingly, it was found that back-switching polarization Pbc increased while the hysteresis area 〈 A 〉, coercive field Ec, saturation polarization Ps, and remnant polarization Pr all decreased linearly with temperature below 398 K (close to the macro-micro domain transition temperature Tnr). A set of simple linear temperature scaling relations was established, which is different from the power-law scaling relations for soft and hard PZT ceramics. At further increased temperature, double-loop features appeared and the ferroelectric properties varied nonlinearly due to the reversible macro-micro domain transition in the T > Tnr region. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Highly (001) oriented ( K, Na) NbO3 ( KNN) lead-free piezoelectric thin films were grown on LaNiO3 ( LNO)-coated silicon by RF magnetron sputtering. The effects of the top electrodes on the electrical properties of KNN thin films were investigated. The dielectric and piezoelectric properties were remarkably improved in LNO/ KNN/ LNO (εr = 899 at 1 kHz, d33 = 58 pm/V), compared with that in Pt/ KNN/ LNO (εr = 584 at 1 kHz, d33 = 26 pm/V). An enhanced ferroelectricity was also obtained in LNO/ KNN/ LNO, with a remnant polarization of 12 μC/cm2 and a maximum polarization of 23 μC/cm2 at the applied field of 200 kV/cm. Besides, the temperature dependence of piezoelectricity of the films was characterized in this study. [ABSTRACT FROM AUTHOR]

Low-temperature sintering of 0.25 PMN-0.40 PT-0.35 PZ ceramics was investigated using CuO as a sintering aid. Effect of CuO on the sinterability, microstructure, and electric properties of 0.25 PMN-0.40 PT-0.35 PZ system was systematically studied. The CuO addition significantly reduced the sintering temperature of 0.25 PMN-0.40 PT-0.35 PZ from 1260°C to 950°C. SEM results indicated that a dense microstructure without any second phase was obtained when the amount of CuO was 0.25 wt%, which gave rise to high values of d33 = 532 pC/N and kp = 58.4%. A large field-induced longitudinal strain ~2.28% (at 30 kV/cm) can also be obtained for 0.25 wt% CuO-added specimens, which shows a great promise for multilayer actuator applications. [ABSTRACT FROM AUTHOR]

The evolution of dynamic hysteresis of lead zirconate titanate stannate antiferroelectric bulk ceramics at various frequencies ( f) and field amplitudes ( E0) has been investigated systematically. A series of asymmetrical minor loops were observed when the working fields were slightly lower than the forward switching field EAF. As E0 increased above EAF, symmetrical double loops appeared and their energy densities w against f and E0 were found to be fit the scaling behavior as w [ABSTRACT FROM AUTHOR]

The doped 0.25 Pb(Mg1/3 Nb2/3) O3-0.40 PbTiO3-0.35 PbZrO3 ( PMN-PZT) ceramics with pure perovskite phase were prepared by one-step oxide-mixed method and conventional columbite method. The phase structure and electrical properties were systematically investigated. Crystallites of the ceramic fabricated by the oxide-mixed method are partially oriented with the c-axis, while samples prepared from columbite method are randomly oriented. This crystalline orientation enabled better electric properties, especially a higher piezoelectric coefficient d33 of 760 pC/N and electromechanical coupling factor kp of 69%. Materials fabricated from the oxide-mixed method are attractive for high-performance piezoelectric actuator and this simple method may have a great prospect in industrial production. [ABSTRACT FROM AUTHOR]

Lead zirconate titanate ceramics with different contents of excess PbO, Zr/Ti ratios, and carbon nanotubes ( CNTs) addition were fabricated by conventional solid-state reaction sintering in air. The effect of PbO content, Zr/Ti ratio, and the addition of CNTs on the formation of intragranular pores in Pb(Zr0.95Ti0.05)O3 ferroelectric ceramics were studied by scanning electron microscopy measurements. It was found that the formation mechanism of porous-grained ceramics is tightly associated with the stoichiometry of PbO and the addition of CNTs. The physical mechanism of the intragranular pore formation, that the insufficiency of PbO and the introduction of the CNTs decrease the densification process by inhibiting mass transportation during sintering stage, was tentatively proposed based on the sintering theory. The ferroelectric properties of the ceramics were characterized and correlated with their microstructures. [ABSTRACT FROM AUTHOR]

Energy-storage properties of 0.89 Bi0.5Na0.5TiO3-0.06 BaTiO3-0.05 K0.5Na0.5NbO3 (0.89 BNT-0.06 BT-0.05 KNN) lead-free ceramics were first investigated. Measurements of dielectric properties together with switching current curves indicate a rather diffuse ferroelectric ( FE) to anti-ferroelectric ( AFE) phase transition when heating from 20°C to 90°C. The energy density ( W), which was calculated from P-E hysteresis loops, increases linearly with the external electric field when E exceeds AFE- FE transition field. W is independent of temperature and frequency, and maintains around 0.59 J/cm3 under 5.6 kV/mm in the stable AFE phase region. These properties indicate that 0.89 BNT-0.06 BT-0.05 KNN ceramics might be a promising lead-free AFE material for energy-storage capacitor application. [ABSTRACT FROM AUTHOR]

PbxSr1-xTiO3 ( PST) thin films with the ratio Pb/Sr = 40/60 were deposited on silicon substrate with Pt or LaNiO3 ( LNO) bottom electrodes by radio frequency magnetron sputtering followed by a postannealing treatment. The structural and microstructural analyses were performed and a perovskite phase was obtained whatever the nature of the bottom electrodes and even at a low temperature (450°C). The optimal annealing temperature is 650°C at which the films have a dense and fine microstructure. For electrical characterization the different top electrodes ( Pt and LNO) were used. In both cases, we demonstrate that PST films present excellent performances in terms of dielectric properties and in particular, the tunability and Figure of Merit. A large tunability (57% at 400 kV/cm) and low dielectric losses (1.4%) were measured at 10 kHz for Pt/PST/Pt structures postannealed at 500°C. For LNO/PST/LNO structures, postannealed at 650°C, the improved tunability (≈80%) and low loss factor (≈2%) were obtained. Prospects of PST as an alternative to BST for tunable applications with a real potentiality of monolithic integration with silicon, in terms of thermal budget, are considered. [ABSTRACT FROM AUTHOR]

Frequency ( f) dependence of coercive field ( Ec) of six Pb( Zr1− x Ti x) O3 (0.20 ≤ x ≤ 0.60) bulk ceramics with different compositions was investigated at various frequencies (1-100 Hz). Scaling relations of Ec against f, Ec ∝ f β, were obtained, where the value of exponent β varied with the ceramics composition. These exponents were far smaller than that of the theoretic prediction because the domain wall motion played a major role in the frequency region. In addition, the values of the exponents were of obvious discrepancy for different phase structures with tetragonal, rhombohedral, and morphotropic phases, but nearly similar for the same phase structure with different compositions, suggesting that different domain structures influence the scaling behaviors. [ABSTRACT FROM AUTHOR]

The hysteresis behaviors and phase characteristics of Pb0.97La0.02(Zr0.90Sn0.025Ti0.075)O3 ( PLZST) ceramics were investigated in this work. A single mini hysteresis loop at 3 kV/mm with the maximum polarization ( Pmax) of 8.3 μC/cm2 and triple hysteresis loops at 6.6 kV/mm were observed, which indicates the coexistence of rhombohedral ferroelectric phase and tetragonal antiferroelectric phase. The X-ray Diffraction patterns and dielectric temperature spectra both demonstrate this coexistence. Moreover, the hysteresis loops with increasing temperature indicated that a ferroelectric-antiferroelectric phase transition occurred at about 60°C. These phenomena would be useful for understanding the domain evolution during ferroelectric and antiferroelectric phase transition. [ABSTRACT FROM AUTHOR]

(Pb,La)(Zr,Ti)O3 antiferroelectric (AFE) ceramics have attracted considerable interest due to their high‐energy storage density and numerous field‐induced phase transitions. However, the positional equilibrium of the A‐site and B‐site is typically maintained without considering that heterovalent doping of La3+ can induce defects within the material, leading to high‐temperature leakage conduction. In this work, we introduced the acceptor ion Na+ at the A‐site simultaneously and designed Pb0.9175–0.5xLa0.055NaxZr0.975Ti0.025O3 (x = 0.01, 0.03, 0.055, 0.07, 0.10) AFE ceramics. The dielectric properties of these ceramics exhibited a consistent pattern of improvement followed by deterioration as the content of Na+ increased. Notably, when x = 0.055 (Na5.5), the AFE ceramic demonstrated superior high‐temperature frequency stability with negligible leakage conduction. Impedance spectroscopy analysis suggested that Na5.5 displays the greatest resistance and highest Edc. Concurrently, the thermally stimulated depolarization current indicates that Na5.5 possesses the lowest defect concentration and the largest Ea. This can be attributed to the internal generation of defect dipole clusters (VPb′′−VO••−NaPb′−LaPb•$V_{{\mathrm{Pb}}}^{{\prime\prime}} - V_{\mathrm{O}}^{ \bullet \bullet } - {\mathrm{Na}}_{{\mathrm{Pb}}}^{\prime} - {\mathrm{La}}_{{\mathrm{Pb}}}^ \bullet $), which effectively restrict the movement of charged defects. These findings suggest that Na5.5 holds significant potential for application and offer insights into the understanding of internal defects in lead‐based AFE materials. [ABSTRACT FROM AUTHOR]

Highly (100) oriented lead strontium titanate ( Pb0.4 Sr0.6 TiO3) thin films were deposited on LaNiO3 -coated Si substrate via radio-frequency magnetron sputtering method with substrate temperature ranging from 300 to 500°C. The PST thin films were crystallized at a temperature as low as 300°C, which may result from the well-controlled stoichiometry and the in situ crystallization on seed layer. At an electric field of 400 kV/cm, high tunability of 43% and 57% can be achieved for PST films deposited at 300°C and 500°C, respectively. Moreover, the dielectric response shows weak frequency dependence and the loss factor stays relatively low. The results suggest that such films should be promising candidate for the microwave tunable devices compatible with the current Si technology. [ABSTRACT FROM AUTHOR]

The (0.9−x) Bi0.5Na0.5TiO3-xBaTiO3-0.1K0.5Na0.5NbO3 [ BNBKN(x), x = 0.060, 0.063, 0.066, and 0.069] ceramics were fabricated by the conventional sintering technique. The P- E hysteresis loops measured under 5 kV/mm at room temperature show that the BNBKN(0.063) ceramics obtain the maximum ( Ps− Pr) value of 20.6 μC/cm2 and the largest energy-storage density W of 0.424 J/cm3. In addition, calculation from the X-ray diffraction results shows that the BNBKN(0.063) ceramics are featured with the largest c/ a ratio of 0.70887. The W is observed to increase with the increase of the c/ a ratio in the BNBKN( x) ceramics. The c/ a ratio can be regarded as a significant factor for W in the BNBKN( x) ceramics. [ABSTRACT FROM AUTHOR]