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High‐performance dielectric capacitors are critical for advanced electronics and electrical power systems. Polymeric dielectrics have been widely investigated for using in dielectric capacitors because of their high dielectric constants, flexibility, low density, and easy processability. However, it is still challenging to achieve simultaneous improvements in both energy density and efficiency in these dielectric polymers. Here, we report ferroelectric polyvinylidene‐fluoride‐based all‐organic dielectric polymer films with continuous compositional gradient structure are reported by modulating the spatial distribution of polymethyl‐methacrylate components, prepared via a facile and scalable additive manufacturing method. The continuous out‐of‐plane composition gradient in the all‐organic dielectric polymer films allows to tune electrical and mechanical behaviors, and thus induces a notably enhanced breakdown strength by modulating the electromechanical breakdown process related to the coupling of local electric field and stress. An ultrahigh discharge energy density of 38.8 J cm−3 along with a high discharge efficiency of >80% is achieved at the electric field of 800 kV mm−1 in the gradient polymer films, which is the highest energy density reported thus far in polymer‐based dielectrics including their nanocomposites and the highest energy efficiency achieved along with an energy density of >30 J cm−3. [ABSTRACT FROM AUTHOR]

Lead based relaxor single crystals have raised a considerable interest due to their outstanding piezoelectric properties. These piezoelectric properties are temperature dependent and are known to decrease when the temperature is decreased. The aim of this paper is to study the variation of the dielectric constant, the elastic compliance, the coupling factor, the piezoelectric charge coefficient, and the mechanical quality factor for rhombohedral single crystals of (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT) poled along [001] in the 5 K-300 K temperature range. In particular, it has been shown that a relaxation phenomenon occurs around 100 K leading to a rapid decrease of the studied piezoelectric, mechanical, and dielectric constants just after a plateau. As a consequence, the similar behaviour of the dielectric constant, piezoelectric charge coefficient, and elastic compliance versus temperature leads to a temperature independent behaviour of the coupling factor above 100 K. This relaxation is also responsible for the minimum observed on the mechanical quality factor. By comparing the measured dielectric constant with the calculated one using the Landau-Ginsburg-Devonshire theory, this relaxation has been attributed to electrical charges freezing within the domain as the temperature is decreased. [ABSTRACT FROM AUTHOR]

Relaxor based Pb(In0.5Nb0.5)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 ternary single crystals (PIN-PMN-PT) were reported to have broader temperature usage range (TR-T) and comparable piezoelectric properties to Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMNT) crystals. In this work, the orientation dependent dielectric, piezoelectric and electromechanical properties for PIN-PMN-PT crystals were investigated along <001> and <110> directions. The electromechanical couplings k33 and k32 for <110> poled crystals were found to be 0.91 and 0.91, respectively, with piezoelectric coefficients d33 and d32 on the order of 925 and -1420 pC/N. Of particular significance was the mechanical quality factor Q33 for <110> oriented crystals, which was found to be ≥500, much higher than the Q values of <001> oriented relaxor-PT crystals (Q∼70–200). The temperature dependence of the piezoelectric properties exhibited good temperature stability up to their ferroelectric phase transition TR-T∼125 °C, indicating <001> and <110> oriented PIN-PMN-PT are promising materials for transducer applications, with the latter for high power resonant devices where low loss (high Q) was required. [ABSTRACT FROM AUTHOR]

The full set of material constants for relaxor-based ternary single crystals Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 (PIN-PMN-PT) were determined and compared to binary Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMNT) crystals. The Curie temperature for rhombohedral compositions of PIN-PMN-PT was found to be in the range of 160–200 °C with ferroelectric rhombohedral to tetragonal phase transition on the order of 120–130 °C, more than 30 °C higher than that found for PMNT. The piezoelectric coefficients (d33) were in the range of 1100–1500 pC/N, with electromechanical coupling factors (k33) about 89%–92% comparable to PMNT crystals. The coercive field of the ternary crystal was found to be 5.5 kV/cm, double the value of the binary counterparts. The dielectric behavior under varying dc bias exhibited a similar trend as observed in PMNT with a much broader usage temperature range. Together with its enhanced field induced phase transition level, the ternary PIN-PMN-PT crystals are promising candidates for high temperature and high drive transducer applications. [ABSTRACT FROM AUTHOR]

Abstract: The high‐energy storage density reported in lead‐free AgNbO3 ceramics makes it a fascinating material for energy storage applications. The phase transition process of AgNbO3 ceramics plays an important role in its properties and dominates the temperature and electric field dependent behavior. In this work, the phase transition behavior of AgNbO3 ceramics was investigated by polarization hysteresis and dielectric tunability measurements. It is revealed that the ferrielectric (FIE) phase at room temperature possesses both ferroelectric (FE)‐like and antiferroelectric (AFE)‐like dielectric responses prior to the critical AFE‐FE transition point. A recoverable energy storage density of 2 J/cm3 was achieved at 150 kV/cm due to the AFE‐FE transition. Based on a modified Laudau phenomenological theory, the stabilities among the AFE, FE and FIE phases are discussed, laying a foundation for further optimization of the dielectric properties of AgNbO3. [ABSTRACT FROM AUTHOR]

The existence of polar nanoregions is the most important characteristic of relaxor-based ferroelectric materials. Recently, the contributions of polar nanoregions to the shear piezoelectric property of relaxor-PbTiO3 (PT) crystals are confirmed in a single domain state, accounting for 50%-80% of room temperature values. For electromechanical applications, however, the outstanding longitudinal piezoelectricity in domain-engineered relaxor-PT crystals is of the most significance. In this paper, the contributions of polar nanoregions to the longitudinal properties in [001]-poled Pb(Mg1/3Nb2/3)O3-0.30PbTiO3 and [110]-poled Pb(Zn1/3Nb2/3)O3-0.15PbTiO3 (PZN-0.15PT) domain-engineered crystals are studied. Taking the [110]-poled tetragonal PZN-0.15PT crystal as an example, phase-field simulations of the domain structures and the longitudinal dielectric/piezoelectric responses are performed. According to the experimental results and phase-field simulations, the contributions of polar nanoregions (PNRs) to the longitudinal properties of relaxor-PT crystals are successfully explained on the mesoscale, where the PNRs behave as 'seeds' to facilitate macroscopic polarization rotation and enhance electric-field-induced strain. The results reveal the importance of local structures to the macroscopic properties, where a modest structural variation on the nanoscale greatly impacts the macroscopic properties. [ABSTRACT FROM AUTHOR]

Microstructural effects on the microwave dielectric properties of (Ba0.4Sr0.6)TiO3 ( BST) polycrystalline ceramics were investigated, focusing on the grain size. Sintering temperatures between 1350°C and 1500°C have a strong effect on the permittivity (880 < ε r < 990), quality factor (570 GHz < Q× f < 1150 GHz), and temperature coefficient of resonant frequency (3920 ppm/°C < τ f < 4560 ppm/°C) at microwave frequency (≈1.4 GHz). The tunable permittivity characteristics (measured at 10 kHz), were also found to be sensitive to the sintering process, demonstrating the possibility of tailoring material property by designed processing. In addition, the effect of the sintering process on grain structure was investigated by XRD calculation and Raman scattering characterization. Less confined phonons were believed to contribute to the enhanced microwave performance as an intrinsic effect (grain size effect), for samples with higher sintering temperature and longer dwell time. On the contrary, the macroscopic properties tend to saturate (or deteriorate), for samples at intensified sintering condition, being thought to be dominated by the extrinsic factors (such as the abundant defects in large grains), as confirmed by the SEM observations. [ABSTRACT FROM AUTHOR]

Lead-free single crystal, (K, Na, Li)(Nb, Ta)O3:Mn, was successfully grown using top-seeded solution growth method. Complete matrix of dielectric, piezoelectric, and elastic constants for [001]C poled single crystal was determined. The piezoelectric coefficient d33 measured by the resonance method was 545 pC/N, which is almost three times that of its ceramic counterpart. The values measured by the Berlincourt meter ( [ABSTRACT FROM AUTHOR]

Ferroelectric materials are the best dielectric and piezoelectric materials known today. Since the discovery of barium titanate in the 1940s, lead zirconate titanate ceramics in the 1950s and relaxor-PT single crystals (such as lead magnesium niobate–lead titanate and lead zinc niobate–lead titanate) in the 1980s and 1990s, perovskite ferroelectric materials have been the dominating piezoelectric materials for electromechanical devices, and are widely used in sensors, actuators and ultrasonic transducers. Energy losses (or energy dissipation) in ferroelectrics are one of the most critical issues for high power devices, such as therapeutic ultrasonic transducers, large displacement actuators, SONAR projectors, and high frequency medical imaging transducers. The losses of ferroelectric materials have three distinct types, i.e., elastic, piezoelectric and dielectric losses. People have been investigating the mechanisms of these losses and are trying hard to control and minimize them so as to reduce performance degradation in electromechanical devices. There are impressive progresses made in the past several decades on this topic, but some confusions still exist. Therefore, a systematic review to define related concepts and clear up confusions is urgently in need. With this objective in mind, we provide here a comprehensive review on the energy losses in ferroelectrics, including related mechanisms, characterization techniques and collections of published data on many ferroelectric materials to provide a useful resource for interested scientists and engineers to design electromechanical devices and to gain a global perspective on the complex physical phenomena involved. More importantly, based on the analysis of available information, we proposed a general theoretical model to describe the inherent relationships among elastic, dielectric, piezoelectric and mechanical losses. For multi-domain ferroelectric single crystals and ceramics, intrinsic and extrinsic energy loss mechanisms are discussed in terms of compositions, crystal structures, temperature, domain configurations, domain sizes and grain boundaries. The intrinsic and extrinsic contributions to the total energy dissipation are quantified. In domain engineered ferroelectric single crystals and ceramics, polarization rotations, domain wall motions and mechanical wave scatterings at grain boundaries are believed to control the mechanical quality factors of piezoelectric resonators. We show that a thorough understanding on the kinetic processes is critical in analyzing energy loss behavior and other time-dependent properties in ferroelectric materials. At the end of the review, existing challenges in the study and control of losses in ferroelectric materials are analyzed, and future perspective in resolving these issues is discussed. [ABSTRACT FROM AUTHOR]

Perovskite ferroelectrics (PFs) have been the dominant piezoelectric materials for various electromechanical applications, such as ultrasonic transducers, sensors, and actuators, to name a few. In this review article, the development of PF crystals is introduced, focusing on the crystal growth and piezoelectric activity. The critical factors responsible for the high piezoelectric activity of PFs (i.e., phase transition, monoclinic phase, domain size, relaxor component, dopants, and piezoelectric anisotropy) are surveyed and discussed. A general picture of the present understanding on the high piezoelectricity of PFs is described. At the end of this review, potential approaches to further improve the piezoelectricity of PFs are proposed. [ABSTRACT FROM AUTHOR]

High-temperature sensors are desirable for structural health monitoring and/or nondestructive evaluation of next-generation turbines, more efficient jet engines, and the furnace components of electrical power plants. Of all the investigated high-temperature piezoelectric materials, rare-earth calcium oxyborate crystals ReCa4O(BO3)3 (ReCOB, Re: rare-earth) exhibit attractive advantages for high-temperature piezoelectric sensing. In this paper, the electroelastic properties of different ReCOB piezoelectric crystals are investigated. The crosstalk between various vibration modes are discussed, from which the optimized crystal cuts are achieved. Furthermore, temperature dependences of the electrical resistivity, dielectric, elastic, piezoelectric, and electromechanical properties of ReCOB crystals are studied. Finally, the thermal properties, including thermal expansion, specific heat, and thermal conductivity at elevated temperatures are studied and compared with commercially available high-temperature piezoelectric crystals. [ABSTRACT FROM AUTHOR]

Pyroelectric properties of the monoclinic ReCa4O(BO3)3 (ReCOB, where Re is rare earth: Y, Gd, Nd, and Pr) single crystals were investigated by the charge integration method in the temperature range of 20°C to 180°C. The two independent pyroelectric coefficients p1 and p3 were measured and their temperature-dependent properties were studied; the pyroelectric p1 was found to be negative and decrease with increasing temperature, varying from -59.3, -64.2, -65.5, and -59.5 μC/(m2?°C) at 30°C to -52.9, -53.3, -46.6, and -50.5 μC/(m2?°C) at 180°C for YCOB, GdCOB, NdCOB, and PrCOB, respectively, whereas the positive coefficient p3 was observed to decrease from 11.6, 13.6, 23.5, and 31.0 μC/(m2?°C) at 30°C to 2.5, 7.1, 4.9, and 10.1 μC/(m2?°C) at 180°C, respectively. In addition, the ReCOB crystals were found to possess relatively high detectivity Fd, being 7.6 to 11.4 x 10-5 Pa-1/2 at 30°C, approximately two times that of commercial triglycine sulfate (TGS) and LiTaO3 crystals, with minimal variations up to 180°C, indicating the potential for use in thermal imaging applications. [ABSTRACT FROM PUBLISHER]

High power characteristics of lead-free ( Bi, Na) Ti O3 ( BNT) and Ba Ti O3 ( BT)-based piezoceramics were investigated and compared to commercial 'hard' Pb( Zr, Ti) O3 PZT materials. Acceptor-modified BNT and BT-based ceramics showed typical 'hardening' characteristics, exhibiting high mechanical quality factor Qm > 800 and low dielectric loss, <0.01, comparable to 'hard' PZT ceramics. Of particular significance is that BNT-based ceramics were found to exhibit minimal variation of resonance frequency shift and high Qm under high level vibration velocity, being ~0.6% and ~800 at 0.25 m/s, respectively, due to the high domain stability associated with their high coercive fields, being on the order of 35 kV/cm. [ABSTRACT FROM AUTHOR]

(1− x)BaTiO3- xBi(Mg1/2Ti1/2)O3 [(1− x)BT- xBMT] polycrystalline ceramics were obtained via solid-state processing techniques. The solubility limit for (1− x)BT- xBMT was determined to be about x=0.07. A systematic structural change from the ferroelectric tetragonal phase to pseudocubic phase was observed at about x≥0.05 at room temperature. Dielectric measurements revealed a gradual change from normal ferroelectric of pure BaTiO3 to highly dispersive relaxor-like characteristics in the solid solution with 30-60 mol% Bi(Mg1/2Ti1/2)O3, showing low-temperature coefficients of capacitance over a wide temperature range. The properties of Nb2O5-doped 0.85BT-0.15BMT ceramics were investigated to better understand the formation mechanism of core-shell structure, for further improving the temperature stability of the dielectric behavior. [ABSTRACT FROM AUTHOR]

In this study, Pb1-x(Yb1/2Nb1/2)0.515Ti0.485O3-x{(2SrO + BaO)/3} [PYNT-SBx] compositions with x = 0.00-0.05 at the rhombohedral side near the morphotropic phase boundary were investigated. The SB substitution for Pb2+ in PYNT was found to increase the tetragonality, but greatly reduce the Curie temperature (Tc) and broaden the dielectric permittivity maximum. The temperature dependence of the relative permittivity follows a Curie-Weiss law above the deviation temperature (TD) at high temperatures for the SB-doped PYNT. The optimized properties with a piezoelectric coefficient of 610 pm V-1, maximum dielectric constant (εmax) of 25,000 (at the Tc = 315°C and 1 kHz), and a remnant polarization (Pr) of 33 µC cm-2 were obtained in PYNT-SB0.04 ceramics. [ABSTRACT FROM AUTHOR]

Perovskite solid solution in the (1− x)[0.4BiScO3–0.6BaTiO3]+ x (K1/2Bi1/2)TiO3 [BSBT–KBT x] system was synthesized using conventional sintering and hot-isostatic pressing. Dielectric properties of BSBT ceramics with different dopant levels of KBT were characterized as a function of temperature and frequency for potential use of high-temperature capacitors. The BSBT ceramics with KBT exhibited high dielectric permittivities (ℇr) (>1700 at RT) and low dielectric loss over the temperature range from 100° to 300°C, with flat temperature coefficients of permittivity (TCℇs). In addition, BSBT ceramics with increasing KBT were observed to possess dielectric relaxation characteristics at temperatures (>RT) as observed in lead-based relaxors. Furthermore, high energy densities, being on the order of 4.0 J/cm3 at 220 kV/cm was observed for the BSBT–KBT20 ceramics from the electric-field polarization behavior. [ABSTRACT FROM AUTHOR]

Modified BiScO3-PbTiO3 (BSPT) tetragonal single crystals were grown using high temperature solution method. The dielectric, piezoelectric and elastic properties of single domain BSPT crystals, after poling along [001] crystallographic direction, have been determined experimentally using the resonance method. The results showed that the BSPT tetragonal crystals possess good piezoelectric properties, with electromechanical coupling factor about 88% and piezoelectric coefficient over 400 pC/N at room temperature. BSPT tetragonal crystals have high Curie temperature around 436 °C and high coercive field ∼28 kV/cm, also, the crystal exhibited a very good temperature stability of the properties till 380 °C. For comparison, the material constants of tetragonal Pb(Zn1/3Nb2/3)O3-PbTiO3 (PZNT) single crystals were measured and listed in this paper. [Copyright &y& Elsevier]

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]

Piezoelectric materials lie at the heart of electromechanical devices. Applications include actuators, ultrasonic imaging, high intensity focused ultrasound, underwater ultrasound, nondestructive evaluation transducer, pressure sensors, and accelerometers, to name a few. In this work, the advantages and disadvantages of relaxor-PbTiO3-based single crystals are discussed, based on the requirements (figure of merit) of various applications, with emphasis on recent developments of the shear properties of single crystals as a function of temperature and applied fields. [ABSTRACT FROM AUTHOR]

The electrical resistivity, dielectric, and electromechanical properties of ReCa4O(BO3)3 (ReCOB; Re = Er, Y, Gd, Sm, Nd, Pr, and La) piezoelectric crystals were investigated as a function of temperature up to 1000°C. Of the studied crystals, ErCOB and YCOB were found to possess extremely high resistivity (p): p ≫ 3 ? 107 ω.cm at 1000°C. The property variation in ReCOB crystals is discussed with respect to their disordered structure. The highest electromechanical coupling factor κ26 and piezoelectric coefficient d26 at 1000°C, were achieved in PrCOB crystals, with values being on the order of 24.7% and 13.1 pC/N, respectively. The high thermal stability of the electromechanical properties, with variation less than 25%, together with the low dielectric loss (≪46%) and high mechanical quality factor (≫1500) at elevated temperatures of 1000°C, make ErCOB, YCOB, and GdCOB crystals promising for ultrahigh temperature electromechanical applications. [ABSTRACT FROM PUBLISHER]

Relaxor-PT based ferroelectric single crystals Pb(Zn1/3Nb2/3)O3ߝPbTiO3 (PZNT) and Pb(Mg1/3Nb2/3)O3ߝPbTiO3 (PMNT) offer high performance with ultra-high electromechanical coupling factors k33s > 0.9 and piezoelectric coefficients d33s > 1500 pC/N. However, the usage temperature range of these perovskite single crystals is limited by TRTߞthe rhombohedral to tetragonal phase transition temperature, which occurs at significantly lower temperatures than the Curie temperature TC, a consequence of curved morphotropic phase boundaries (MPBs). Furthermore, these ?001?-oriented crystals exhibit low mechanical quality Q and coercive fields, restricting their usage in high-power applications. In this survey, recent developments on binary and ternary perovskite relaxor-PT crystal systems are reviewed with respect to their temperature usage range. General trends of dielectric and piezoelectric properties of relaxor-PT crystal systems are discussed in relation to their respective TC/TRT. In addition, two approaches have been implemented to improve mechanical Q, including acceptor dopants, analogous to hard polycrystalline ceramics, and anisotropic domain engineering, enabling lowloss crystals with high coupling for high-power applications. [ABSTRACT FROM PUBLISHER]

The dielectric and piezoelectric properties of [111]-oriented orthorhombic Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT) single crystals (3O multi-domain state) with various domain sizes were investigated by poling control. The free dielectric permittivity and longitudinal piezoelectric coefficient (d 33) were 6400 and 900pCN−1, respectively, for samples with domain sizes of ∼2μm, nearly twice that of ∼20μm. Together with good temperature stability ( <8%) up to the orthorhombic–tetragonal phase transition temperature, the “3O” PMN–PT crystals with fine domain structures are promising candidate for sensors and transducers. [Copyright &y& Elsevier]

BaTiO3-based ceramics with a multilayer core–shell structure were designed using BaTiO3–Bi(Mg1/2Ti1/2)O3 as the shell-II (outer layer) composition, and fabricated by two different approaches with a two-step sintering method. The samples produced by approach B (combined sol–gel coating with solid mixing methods) were found to possess optimized temperature stability of dielectric behavior in the temperature range of −55 to 150°C (ΔC/C 25°C <±15%), together with a high dielectric constant and low dielectric loss, being on the order of 1500–1900 (1kHz) and <1.5%, respectively, at room temperature, and make it promising for dielectric applications at elevated temperature. [ABSTRACT FROM AUTHOR]

Abstract: (1− x)Pb(Sn1−y Ti y )O3–xPb(Mg1/3Nb2/3)O3 (x =0.1–0.4, y =0.45–0.65) ternary system was prepared using two-step columbite precursor method. Phase structure of the synthesized ceramics was studied by using X-ray powder diffraction and the morphotropic phase boundary (MPB) curve of the ternary system was confirmed. The isothermal map of Curie temperature (T C) in the phase diagram was obtained based on the dielectric–temperature measurements. The coercive field E C and internal bias field E i were found to increase with increasing PT content, while decrease with increasing PMN content. The optimum properties were achieved in the MPB composition 0.8Pb(Sn0.45Ti0.55)O3–0.2Pb(Mg1/3Nb2/3)O3, with dielectric permittivity ɛ r, piezoelectric coefficient d 33, planar electromechanical coupling k p, mechanical quality factor Q m and T C of being on the order of 3040, 530pC/N, 55.5%, 320 and 190°C, respectively, exhibiting potential usage for high power application. [Copyright &y& Elsevier]

Abstract: yPb(In1/2Nb1/2)O3–(1− x − y)Pb(Mg1/3Nb2/3)O3–xPbTiO3 (yPIN–(1− x − y)PMN–xPT) polycrystalline ceramics with morphotropic phase boundary (MPB) compositions were synthesized using columbite precursor method. X-ray diffraction results indicated that the MPB of PIN–PMN–PT was located around PT=0.33–0.36, confirmed by their respective dielectric, piezoelectric and electromechanical properties. The optimum properties were found for the MPB composition 0.36PIN–0.30PMN–0.34PT, with dielectric permittivity ɛ r of 2970, piezoelectric coefficient d 33 of 450pC/N, planar electromechanical coupling k p of 49%, remanent polarization P r of 31.6μC/cm2 and T C of 245°C. According to the results of dielectric and pyroelectric measurements, the Curie temperature T C and rhombohedral to tetragonal phase transition temperature T R–T were obtained, and the “flat” MPB for PIN–PMN–PT was achieved, indicating that the strongly curved MPB in PMN–PT system was improved by adding PIN component, offering the possibility to grow single crystals with high electromechanical properties and expanded temperature usage range (limited by T R–T). [Copyright &y& Elsevier]

Abstract: (K0.5Na0.5)NbO3 (KNN) single crystals were grown using a high temperature flux method. The dielectric permittivity was measured as a function of temperature for [001]-oriented KNN single crystals. The ferroelectric phase transition temperatures, including the rhombohedral–orthorhombic , orthorhombic–tetragonal and tetragonal–cubic were found to be located at −149  ∘C, 205 ∘C and 393 ∘C, respectively. The domain structure evolution with an increasing temperature in [001]-oriented KNN single crystal was observed using polarized light microscopy (PLM), where three distinguished changes of the domain structures were found to occur at −150  ∘C, 213 ∘C and 400 ∘C, corresponding to the three phase transition temperatures. [Copyright &y& Elsevier]

A series of Bi 0.5- x Er x Na 0.4 K 0.1 TiO 3 (BNKT- x Er) ceramics were designed and fabricated, the dopant effects on dielectric, piezoelectric and photoluminescence properties were studied. The results show that the piezoelectric property of BNKT can be enhanced by a trace amount of Er dopant, which is also reflected in the large linear electrostrain (S uni = 0.29%, under 55 kV/cm) achieved in BNKT-0.0025 Er. On the other hand, higher Er content can produce excellent dielectric temperature stability, with △ ԑ / ԑ 150 °C < ±15% over temperature range of 90∼510 °C. Meanwhile, all BNKT- x Er ceramics exhibit good photoluminescence properties, which may open new applications of these multifunctional ceramics. [ABSTRACT FROM AUTHOR]

The property degradation observed in thin Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT) crystals is believed to relate to large domains and subsequent clamping induced by the surface boundary. In this work, the properties were investigated as function of domain size, using controlled poling. The degraded piezoelectric and dielectric properties of thin PMN–PT were found to increase significantly with decreasing domain size. Furthermore, the fine domain structure was found to be stable at 3kVcm−1 after 7.0×105 negative-pulse cycles. These properties make PMN–PT crystals suitable for high-frequency (>20MHz) ultrasound transducers. [Copyright &y& Elsevier]

Abstract The projected increase in world energy consumption within the next 50 years, coupled with low emission requirements, has inspired an enormous effort towards the development of efficient, clean, and renewable energy sources. Efficient electrical energy storage solutions are keys to effective implementation of the electricity generated from these renewable sources. In step with the development of energy storage technology and the power electronics industry, dielectric materials with high energy density are in high demand. The dielectrics with a medium dielectric constant, high breakdown strength, and low polarization hysteresis are the most promising candidates for high-power energy storage applications. Inspiring energy densities have been achieved in current dielectrics, but challenges exist for practical applications, where the underlying mechanisms need to be understood for further enhancing their properties to meet future energy requirements. In this review, we summarize the principles of dielectric energy-storage applications, and recent developments on different types of dielectrics, namely linear dielectrics, paraelectrics, ferroelectrics, and antiferroelectrics, are surveyed, focusing on perovskite lead-free dielectrics. The new achievements of polymer-ceramic composites in energy-storage applications are also reviewed. The pros and cons of each type of dielectric, the existing challenges, and future perspectives are presented and discussed with respect to specific applications. [ABSTRACT FROM AUTHOR]

The effect of (Li,Ce) substitution at the A-site on the properties of Na0.25K0.25Bi4.5Ti4O15 (NKBT)-based ceramics was investigated. The piezoelectric coefficient d 33 of the [(Na0.5K0.5)Bi]0.42(LiCe)0.04[]0.04Bi4Ti4O15 ceramic was found to be 25pCN−1, the highest value of the NKBT-based ceramics, and almost twice the d 33 values of pure NKBT ceramics (∼13pCN−1). The thickness coupling factor k t was found to be 20%, which, together with the high T C (∼615°C) and stable piezoelectric properties, suggests that (Li,Ce)-modified NKBT-based materials are promising candidates for high-temperature applications. [Copyright &y& Elsevier]