Showing papers on "Ferroelectric ceramics published in 2015"
TL;DR: The results show that the grain size effect on the dielectric permittivity is nearly independent of the sintering method and starting powder used, which suggests that besides domain wall density, other factors such as back fields and point defects, which influence the domain wall mobility, could be responsible for the different grain size dependence observed in thedielectric and piezoelectric/ferroelectric properties.
Abstract: Grain size effects on the physical properties of polycrystalline ferroelectrics have been extensively studied for decades; however there are still major controversies regarding the dependence of the piezoelectric and ferroelectric properties on the grain size. Dense BaTiO3 ceramics with different grain sizes were fabricated by either conventional sintering or spark plasma sintering using micro- and nano-sized powders. The results show that the grain size effect on the dielectric permittivity is nearly independent of the sintering method and starting powder used. A peak in the permittivity is observed in all the ceramics with a grain size near 1 μm and can be attributed to a maximum domain wall density and mobility. The piezoelectric coefficient d33 and remnant polarization Pr show diverse grain size effects depending on the particle size of the starting powder and sintering temperature. This suggests that besides domain wall density, other factors such as back fields and point defects, which influence the domain wall mobility, could be responsible for the different grain size dependence observed in the dielectric and piezoelectric/ferroelectric properties. In cases where point defects are not the dominant contributor, the piezoelectric constant d33 and the remnant polarization Pr increase with increasing grain size.
239 citations
TL;DR: In this paper, the PMN-10PT relaxor ceramic exhibits a relatively large electrocaloric change of temperature ΔTEC> 1 K at room temperature, and the experimental testing of the cooling device demonstrates the efficient regeneration and establishment of the temperature span between the hot and cold sides of the regenerator.
Abstract: The electrocaloric effect (ECE), i.e., the conversion of the electric into the thermal energy has recently become of great importance for development of a new generation of cooling technologies. Here, we explore utilization of [Pb(Mg1∕3Nb2∕3)O3]0.9[PbTiO3]0.1 (PMN-10PT) relaxor ceramics as active elements of the heat regenerator in an ECE cooling device. We show that the PMN-10PT relaxor ceramic exhibits a relatively large electrocaloric change of temperature ΔTEC > 1 K at room temperature. The experimental testing of the cooling device demonstrates the efficient regeneration and establishment of the temperature span between the hot and the cold sides of the regenerator, exceeding several times the ΔTEC within a single PMN-10PT ceramic plate.
140 citations
TL;DR: In this article, the performance of a variety of material types are compared, including ferroelectric ceramics, polymers, and liquid crystals, and the most promising material types for microwave applications are polymers and liquid crystal.
Abstract: Microwave devices based on tunable materials are of vigorous current interest. Typical applications include phase shifters, antenna beam steering, filters, voltage controlled oscillators, matching networks, and tunable power splitters. The objective of this review is to assist in the material selection process for various applications in the microwave regime considering response time, required level of tunability, operating temperature, and loss tangent. The performance of a variety of material types are compared, including ferroelectric ceramics, polymers, and liquid crystals. Particular attention is given to ferroelectric materials as they are the most promising candidates when response time, dielectric loss, and tunability are important. However, polymers and liquid crystals are emerging as potential candidates for a number of new applications, offering mechanical flexibility, lower weight, and lower tuning voltages.
133 citations
TL;DR: In this article, the electrocaloric effect in lead-free Zr doped Ba08Ca02(ZrxTi1−x)O3 (BCTZ) ceramics was investigated.
Abstract: The electrocaloric effect was investigated in lead-free Zr doped Ba08Ca02(ZrxTi1−x)O3 (BCTZ) ceramics synthesized by a conventional sintering process Room-temperature x-ray diffraction analysis showed that the tetragonal structure is obtained in BCTZ for x ≤ 008 and a pseudo cubic phase for x > 008 The dielectric spectroscopy and calorimetry revealed that the Curie temperature decreases as a consequence of Zr doping and that the BCTZ exhibits a first order ferroelectric phase transition The electrocaloric effect was determined by the calculation of the electrocaloric change of temperature (ΔT) using the Maxwell relation based on the P–E hysteresis loops measured at different temperatures A large electrocaloric responsivity ΔT/ΔE = 034 × 10−6 Km/V was found for x = 004, which significantly exceeds of values found so far in other lead-free electrocaloric materials
129 citations
TL;DR: In this paper, the electrocaloric effect in bulk ceramics 0.65Ba(Zr0.2Ti0.8)O3-x(Ba0.7Ca0.3)TiO3 was measured using a modified differential scanning calorimeter.
Abstract: Solid solutions of (1 − x)Ba(Zr0.2Ti0.8)O3-x(Ba0.7Ca0.3)TiO3 promise to exhibit a large electrocaloric effect (ECE), because their Curie temperature and a multiphase coexistence region lie near room temperature. We report on direct measurements of the electrocaloric effect in bulk ceramics 0.65Ba(Zr0.2Ti0.8)O3-0.35(Ba0.7Ca0.3)TiO3 using a modified differential scanning calorimeter. The adiabatic temperature change reaches a value of ΔTEC = 0.33 K at ∼65 °C under an electric field of 20 kV/cm. It remains sizeable in a broad temperature interval above this temperature. Direct measurements of the ECE proved that the temperature change exceeds the indirect estimates derived from Maxwell relations by about ∼50%. The discrepancy is attributed to the relaxor character of this material.
123 citations
TL;DR: In this paper, the upconversion emission intensities of Ho/Yb-codoped Ba0.77Ca0.23TiO3 ferroelectric ceramics were investigated under the excitation of 980-nm.
116 citations
TL;DR: In this paper, the electrocaloric effect (ECE) of the lead-free relaxor ferroelectric 0.85K0.5NbO3-0.15SrTiO3 (KNN-STO) ceramics is investigated.
Abstract: The electrocaloric effect (ECE), i.e., the adiabatic temperature change ΔTEC, of the lead-free relaxor ferroelectric 0.85K0.5Na0.5NbO3-0.15SrTiO3 (KNN-STO) ceramics is investigated. The ECE data obtained by a direct method show the existence of a large ECE near the temperature of the dielectric permittivity maximum. Due to the high break-down electric field, a large ΔTEC exceeding 1.2 K at 300 K and 1.9 K at 340 K was observed at 159 kV/cm in a broad temperature range of 80 K. Such a high ECE response near the room temperature is comparable to that found in lead-based ceramic materials, thus making KNN-STO a strong candidate to replace lead-based materials in future electrocaloric applications.
104 citations
TL;DR: In this paper, structural, electrical, and light up conversion properties of Erbium (Er) substituted bismuth titanate (Bi4� xErxTi3O12) ceramics have been investigated.
98 citations
TL;DR: In this paper, the room temperature ferroelectric hysteresis loops are observed in these ceramics, and a polar orthorhombic structure with two oxygen tilting modes has been confirmed by the X-ray powder diffraction.
Abstract: The hybrid improper ferroelectricity (HIF) has been proposed as a promising way to create multiferroic materials with strong magnetoelectric coupling by the first-principle calculation, and the experimental evidences of HIF in Ruddlesden-Poper Ca3(Ti1−xMnx)2O7 (x = 0, 0.05, 0.1, and 0.15) ceramics have been shown in the present work. The room temperature ferroelectric hysteresis loops are observed in these ceramics, and a polar orthorhombic structure with two oxygen tilting modes has been confirmed by the X-ray powder diffraction. A first-order phase transition around 1100 K in Ca3Ti2O7 was evidenced, and the temperatures of phase transitions decrease linearly with increasing of the contents of Mn4+ ions. Based on the result of first-principle calculations, the polarization should be reversed by switching through the mediated Amam phase in Ca3Ti2O7 ceramics.
82 citations
TL;DR: In this article, an overview of energy harvesting using ferroelectric materials, with a particular focus on the energy harvesting capabilities of porous Ferroelectric ceramics for both piezo and pyroelectric harvesting.
Abstract: This paper provides an overview of energy harvesting using ferroelectric materials, with a particular focus on the energy harvesting capabilities of porous ferroelectric ceramics for both piezo- and pyroelectric harvesting. The benefits of introducing porosity into ferro- electrics such as lead zirconate titanate (PZT) has been known for over 30 years, but the potential advantages for energy harvesting from both ambient vibrations and temperature fluctuations have not been studied in depth. The article briefly discusses piezoelectric and pyro- electric energy harvesting, before evaluating the potential benefits of porous materials for increasing energy harvesting figures of merits and electromechanical/electrothermal coupling factors. Established processing routes are evaluated in terms of the final porous structure and the resulting effects on the electrical, thermal and mechanical properties.
70 citations
TL;DR: In this paper, the effects of BaTiO3 template amount on the [001] orientation degree, microstructure, and resulting changes in dielectric, piezoelectric and ferroelectric properties of PIN-PMN-PT were investigated.
Abstract: [001] oriented relaxor based ternary Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) ceramics were fabricated by templated grain growth. The effects of BaTiO3 template amount on the [001] orientation degree, microstructure, and resulting changes in dielectric, piezoelectric, and ferroelectric properties of PIN-PMN-PT were investigated. A high [001] texture fraction of 93% was achieved in the PIN-PMN-PT ceramics at 5 vol. % BaTiO3 template. Giant electromechanical properties (d33* = 1555 pC/N, d33 = 824 pC/N, and kp = 0.81) and high ferroelectric properties (Ec = 8.3 kV/cm and Pr = 31 μC/cm2) were obtained from those highly textured ceramics, which are much superior to those of randomly oriented counterpart. Furthermore, the textured ternary ceramics exhibited remarkably improved phase transition temperatures (Tr-t = 120 °C and Tc = 203 °C) compared with previously reported binary PMN-PT textured ceramics. The domain structure was characterized by piezoelectric force microscopy, and domain contributi...
TL;DR: In this paper, the dielectric properties of perovskite structured (Ba 085 Ca 015 )(Zr 01 Ti 09 )O 3 ; [BCZT], ferroelectric ceramics prepared by the conventional solid-state reaction method were investigated by AC impedance spectroscopy.
TL;DR: In this article, a broad dielectric constant peak was observed over a wide temperature range around the phase transition temperature and the presence of non-Debye type of relaxation has been confirmed by the complex impedance analysis.
TL;DR: In this article, the properties of CaBi4Ti4O15 (CBT), CaBi 4Ti3.95Nb0.05O15(CBTN), and CaBi5.2.2% MnO2 ceramics with bismuth layer structure were studied.
TL;DR: In this paper, the authors investigated the electrocaloric effect in lead-free Ba 0.94 Ca 0.06 Ti 1Ax Sn x O 3 ceramics using an indirect method.
Abstract: Electrocaloric effect in lead-free Ba 0.94 Ca 0.06 Ti 1Ax Sn x O 3 ceramics is studied using an indirect method. The Ba 0.94 Ca 0.06 Ti 0.87 5Sn 0.125 O 3 ceramic located near a multi-phase point shows best electrocaloric performance, which provides further experimental evidence for optimizing electro-caloric properties through constructing multiphase coexistence. Giant electrocaloric efficiency ($0.4 K mm/kV) is achieved in this ceramic at about room temperature at a low electric field of 6 kV/cm. While large electrocaloric temperature ($0.63 K) is obtained by further enhancing electric field (20 kV/cm), a decrease in electrocaloric efficiency (0.32 K mm/kV) is simultaneously observed, which is attributed to phase transition from first-order to more diffusive second-order under higher electric field. V C 2015 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4938134] Electrocaloric (EC) effect has attracted increasing interest during the past decades due to their potential applications in environment-friendly solid-state cooling devices. 1–3 The polarization of ferroelectric materials changes under an external electric field. The phenomenon related to the changes in both temperature and entropy induced by the change in polarization of the material under an electric field is called EC effect. Since the discovery of giant EC effect (DT ¼ 12 K at 226 C) in PbZr 0.95 Ti 0.05 O 3 thin film, 4 extensive studies have been devoted to the investigations of EC effect in a variety of ferroelectric/antiferroelectric/relaxor materials, such as bulk materials (ceramics 5–7 or single crystals 8–10
TL;DR: In this article, polycrystalline lead-free Sodium Bismuth Titanate (NBT) ferroelectric ceramics doped with rare earth (RE) element are prepared using solid state reaction method.
Abstract: Polycrystalline lead-free Sodium Bismuth Titanate (NBT) ferroelectric ceramics doped with rare earth (RE) element are prepared using solid state reaction method. Optical, ferroelectric, and electrocaloric properties were investigated. The introduction of RE3+ ions in the NBT host lattice shows different light emissions over the wavelength range from visible to near infrared region. The ferroelectric P-E hysteresis loops exhibit an antiferroelectric-like character near room temperature indicating possible existence of a morphotropic phase boundary. The enhanced electrocaloric response was observed in a broad temperature range due to nearly merged phase transitions. Coexistence of optical and electrocaloric properties is very promising for photonics or optoelectronic device applications.
TL;DR: In this paper, an electric field-temperature (E-T) phase diagram for a lead-free 0.5 mol. Mn-doped Bi(Na 0.1K0.9)0.5TiO3 ceramics was investigated.
Abstract: An electric field–temperature (E-T) phase diagram for a lead-free 0.5 mol. % Mn-doped Bi(Na0.1K0.9)TiO3 ceramics was investigated. The x-ray diffraction, dielectric and polarization measurements revealed relaxor behavior and were used to characterize the stability regions of the non-ergodic relaxor, ergodic relaxor and electric field induced ferroelectric states. As indicated by the polarization–current density profiles, transformation between two electric fields, induced ferroelectric states with opposite polarization direction arise via a two-step process through an intermediate relaxor state. Interplay between the ferroelectric state conversion and intermediate relaxor state is governed by the dynamics of polarization relaxation. The presented E-T phase diagram revealed the effects of the applied electric field and temperature on stability regions. This is of special interest since the Bi0.5(Na0.1K0.9)0.5TiO3 ceramics were proposed as a potential piezoceramic material.
TL;DR: In this paper, residual ferroelectricity is observed in barium strontium titanate ceramics over 30°C above the global phase transition temperature, in the same temperature range in which anomalously large flexoelectric coefficients are reported.
Abstract: Residual ferroelectricity is observed in barium strontium titanate ceramics over 30 °C above the global phase transition temperature, in the same temperature range in which anomalously large flexoelectric coefficients are reported. The application of a strain gradient leads to strain gradient-induced poling or flexoelectric poling. This was observed by the development of a remanent polarization in flexoelectric measurements, an induced d33 piezoelectric response even after the strain gradient was removed, and the production of an internal bias of 9 kV m−1. It is concluded that residual ferroelectric response considerably enhances the observed flexoelectric response.
TL;DR: In this paper, a large electrocaloric effect (ECE) near room temperature is reported in Sn doped BaTiO3 ceramics, which also exhibit relaxor ferroelectric response to near the invariant critical point.
Abstract: A large electrocaloric effect (ECE) near room temperature is reported in Sn doped BaTiO3 ceramics. By tuning Ba(Ti1−xSnx)O3 compositions which also exhibit relaxor ferroelectric response to near the invariant critical point, the Ba(Ti1−xSnx)O3 bulk ceramics at x ∼ 0.12 exhibit a large EC coefficient (ΔT/ΔE =0.27*10−6K⋅mV−1) over a 50 K temperature range. In addition to that, the diffuse phase transition is successfully applied to broaden the EC peaks under low electric field. These properties added together indicate a general solution of the electrocaloric materials with high performance for practical cooling applications.
TL;DR: In this paper, the authors used the Maxwell's relationship for elastocaloric effect in bulk O3 polycrystalline ferroelectric material to demonstrate the potential of the material for refrigeration.
Abstract: Elastocaloric effect has been experimentally demonstrated in bulk (Ba085Ca015)(Zr01Ti09)O3 polycrystalline ferroelectric material Predictions were made using Maxwell's relationship for elastocaloric effect A maximum elastocaloric effect of 155 K was observed for an initial material temperature of 340 K and applied compressive stress of 0–250 MPa (under a constant electric field of 2 MV m−1) The reported value is several times larger than the peak electrocaloric effect for the same material The results indicate that ferroelectric materials possess a huge potential for elastocaloric refrigeration
TL;DR: In this paper, the domain structure and domain wall motion play important roles on the piezoelectric properties of hot-pressed (K0.50Na 0.50)NbO3 (KNN) ceramics before and after poling were studied by observing the domain patterns with an acid-etching technique.
Abstract: Domain structure and domain wall motion play important roles on the piezoelectric properties of ferroelectric ceramics. In this work, the domain structure of hot-pressed (K0.50Na0.50)NbO3 (KNN) ceramics before and after poling were studied by observing the domain patterns with an acid-etching technique, and the extrinsic contribution to the piezoelectric properties were evaluated. It was found that the domain structure of the unpoled KNN ceramic was relatively complicated with many watermark, herringbone and zigzag patterns, while only a single set or few sets of parallel domain stripes were observed in the poled KNN ceramic, due to the domain reorientation and domain wall motion during the poling process. The average domain width changes from 200 (±10) nm before poling to 250 (±10) nm after poling. Domain configurations of “Herringbone-Zigzag-Watermark” and “Herringbone- Herringbone-Zigzag” types observed in the unpoled KNN ceramic were then further analyzed. The extrinsic contribution to the piezoelectric properties from the domain reorientation and irreversible domain wall motion in the hot-pressed KNN ceramic was found to be 71%, slightly higher than that of conventional sintered KNN ceramics ~68%.
TL;DR: In this article, the authors systematically investigated the phenomenon of internal clamping in ferroelectric materials through the formation of glass-ceramic composites and found that glass incorporation could systematically increase diffuse phase transition and relaxor behavior temperature range from 70 K to 81K and 20K to 34 K, respectively when 6% and 4% glass content is added which indicates addition of glass provides better temperature stability.
Abstract: This study systematically investigates the phenomenon of internal clamping in ferroelectric materials through the formation of glass-ceramic composites. Lead-free 0.715Bi(0.5)Na(0.5)TiO(3)-0.065BaTiO(3)-0.22SrTiO(3) (BNT-BT-ST) bulk ferroelectric ceramic was selected for the course of investigation. 3BaO - 3TiO(2) - B2O3 (BTBO) glass was then incorporated systematically to create sintered samples containing 0%, 2%, 4% and 6% glass (by weight). Upon glass induction features like remnant polarization, saturation polarization, hysteresis losses and coercive field could be varied as a function of glass content. Such effects were observed to benefit derived applications like enhanced energy storage density similar to 174 k J/m(3) to similar to 203 k J/m(3) and pyroelectric coefficient 5.7x10(-4) Cm-2K-1 to 6.8x10(-4) Cm-2K-1 by incorporation of 4% glass. Additionally, BNT-BT-ST depolarization temperature decreased from 457K to 431K by addition of 4% glass content. Glass incorporation could systematically increases diffuse phase transition and relaxor behavior temperature range from 70 K to 81K and 20K to 34 K, respectively when 6% and 4% glass content is added which indicates addition of glass provides better temperature stability. The most promising feature was observed to be that of dielectric response tuning. It can be also used to control (to an extent) the dielectric behavior of the host ceramic. Dielectric permittivity and losses decreased from 1278 to 705 and 0.109 to 0.107 for 6% glass, at room temperature. However this reduction in dielectric constant and loss increases pyroelectric figures of merit (FOMs) for high voltage responsivity (F-v) high detectivity (F-d) and energy harvesting (F-e) from 0.018 to 0.037 m(2)C(-1), 5.89 to 8.85 mu Pa-1/2 and 28.71 to 61.55 Jm(-3)K(-2), respectively for 4% added ceramic-glass at room temperature. Such findings can have huge implications in the field of tailoring ferroelectric response for application specific requirements. (C) 2015 Author(s).
TL;DR: In this article, the lead free (1− x )Na 05 Bi 05 TiO 3 - x BaTiO 3 /NBT-x BT (where x =005, 006, 007, and 008) ferroelectric ceramics were synthesized in single perovskite phase by solid state reaction route.
TL;DR: In this paper, the dielectric, piezoelectric and upconversion photoluminescence properties of PMN-xPT:Er ceramics with different PT contents are investigated.
Abstract: (0.97-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3-0.03Pb(Er1/2Nb1/2)O3 (PMN-xPT:Er) ceramics with different PT contents are prepared. The dielectric, piezoelectric, ferroelectric, and upconversion (UC) photoluminescence properties of the ceramics are investigated. The crystal structure of PMN-xPT:Er evolves from rhombohedral to the morphotropic phase boundary (MPB), and then to the tetragonal phase as the PT content increases. The ratio of red to green emission intensities of UC emission is strongly correlated with the phase structure of the host PMN-xPT:Er ceramic. The origin of this correlation is discussed based on Judd-Ofelt theory. Furthermore, based on the evolution of crystal symmetry of the PMN-xPT:Er ceramics, the crystal structure of the MPB phase of PMN-xPT is suggested.
TL;DR: In this paper, the energy harvesting capabilities of bulk lead-free ferroelectric materials using Olsen cycle was demonstrated, and the maximum harness-able energy density for KNTM and BZT-50BCT compositions were found to be 629 J/L (629 KJ/m3) and 87 J /L (87 KJ /m3), respectively.
Abstract: This article demonstrates the energy harvesting capabilities of bulk lead-free ferroelectric materials using Olsen cycle. Lead-free compositions K[(Nb0.90Ta0.10)0.99Mn0.01]O3 (KNTM) and 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 (BZT-50BCT) have been explored for their energy harvesting capabilities. Further, we studied the variation in energy density over wide range of applied temperature and electric field. The maximum harness-able energy density for KNTM and BZT-50BCT compositions are found to be 629 J/L (629 kJ/m3) and 87 J/L (87 kJ/m3), respectively. This estimated energy density, obtained for the bulk samples, is comparable with the highest energy density reported to-date (888 J/L for lanthanum-doped lead zirconate titanate (8/65/35 PLZT) thick films).
TL;DR: In this paper, a relaxor ferroelectric ceramic, 0.67Pb(Mg1/3Nb2/3)O3-0.33PbTiO3 (PMN-PT), was synthesized by a molten-salt growth method with lower remnant polarization and slimmer hysteresis loops.
Abstract: In this study, a relaxor ferroelectric ceramic, 0.67Pb(Mg1/3Nb2/3)O3–0.33PbTiO3 (PMN–PT), was synthesized by a molten-salt growth method with lower remnant polarization and slimmer hysteresis loops than traditional ferroelectric ceramics. The PMN–PT particles remained homogeneously dispersed in the composite and adhered tightly to a poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) matrix due to the modification of the particles with dopamine. The composites had a maximum dielectric constant of 65.1 and a low dielectric loss of less than 0.037 at 1 kHz. Due to the low remnant polarization of the relaxor ferroelectric ceramic of PMN–PT, the energy density of the composites significantly increased. The discharged energy density of the sample with 50 vol% PMN–PT was 4 times that of P(VDF-HFP) at 80 kV mm−1. It was demonstrated that the dopamine functionalized PMN–PT/P(VDF-HFP) composite was a potential dielectric material with potential future applications in energy storage.
TL;DR: In this article, phase-pure (Bi 1/2K1/2)TiO3 (BKT) ceramics with various average grain sizes from 0.18 to 1.01μm were prepared from a hydrothermally synthesized powder and their phase transition behaviors were studied by means of dielectric measurements.
Abstract: Dense and phase-pure (Bi1/2K1/2)TiO3 (BKT) ceramics with various average grain sizes from 0.18 to 1.01 μm were prepared from a hydrothermally synthesized powder and their phase transition behaviors were studied by means of dielectric measurements. A drastic increase of the maximum dielectric permittivity (em) with increasing the grain size was found in the temperature dependence of permittivity. The sample with the largest grain size clearly showed both a frequency dependence of dielectric maximum temperature (Tm) and a dielectric anomaly with a strong thermal hysteresis at a temperature below Tm, demonstrating that the BKT ceramic is intrinsically a material exhibiting a spontaneous relaxor to normal ferroelectric (R-nFE) phase transition. On the other hand, the suppression of the R-nFE transition was observed in the sample with the smallest grain size, which was explained as an effect of avoiding the internal stress development caused by the volume increase occurring with the phase transition.
TL;DR: In this article, the authors investigated multiple caloric effects for Fe-doped bulk (Ba0.865Ca0.135Zr0.1089Ti0.8811Fe0.01)O3 (BCZTO-Fe) ferroelectric ceramic.
Abstract: Multiple caloric effects have been investigated for Fe-doped bulk (Ba0.865Ca0.135Zr0.1089Ti0.8811Fe0.01)O3 (BCZTO-Fe) ferroelectric ceramic. Indirect predictions were made using Maxwell's relations in conjunction with data from experimental observations. It was revealed that bulk BCZTO-Fe has huge untapped potential for solid-state refrigeration. A peak electrocaloric effect of 0.45 K (347 K) was predicted for 0–3 kV.mm−1 electric field, significantly higher than other BCZTO based materials. A maximum elastocaloric cooling of 1.4 K (298 K) was achieved for applied stress of 0–200 MPa. Finally, an unforeseen component of electric field driven caloric effect has been reported as inverse piezocaloric effect, with a maximum temperature change of 0.28 K (298 K).
TL;DR: In this paper, the influence of chemical modification and electrical poling on the AFE/FE phase stability was investigated, primarily focusing on the microstructural and crystallographic evolutions.
Abstract: We recently developed a feasible crystal chemistry strategy to stabilize the antiferroelectricity in NaNbO3 through a chemical substitution to decrease the tolerance factor and increase the average electronegativity of the system [Shimizu et al., Dalton Trans. 44, 10763 (2015) and Guo et al., J. Appl. Phys. 117, 214103 (2015)]. Two novel lead-free antiferroelectric (AFE) solid solutions, (1-x)NaNbO3-xCaZrO3 and (1-x)NaNbO3-xSrZrO3, have been found to exhibit the double polarization hysteresis typical of a reversible AFE ↔ ferroelectric (FE) phase transition. In this study, as demonstrated by (1-x)NaNbO3-xCaZrO3 system, the influence of chemical modification and electrical poling on the AFE/FE phase stability was investigated, primarily focusing on the microstructural and crystallographic evolutions. Together with the macroscopic polarization hysteresis measurements, a well-demonstrated structure-property relationship was presented. It was found that the CaZrO3 substitution into NaNbO3 can effectively destabilize the FE Q phase and correspondingly lead to a spontaneous reverting to AFE P phase. In contrast to the reversible AFE ↔ FE phase transition, the domain morphology evolution exhibits irreversible nature with a growing process of the orientational domains after applying electric field. Moreover, a multiple-zone axes electron diffraction map of P and Q phases has been summarized and is believed to be an efficient diagram to determine the AFE/FE nature of the NaNbO3-based systems.
TL;DR: In this paper, the authors modified the symmetry of poled PZT ceramics from transversally isotropic to orthogonal through ferroelastic domain switching by applying a high lateral stress along the 2-direction and holding the stress for several hours.
Abstract: The piezoelectric face-shear ( d36) mode may be the most useful shear mode in piezoelectrics, while currently this mode can only exist in single crystals of specific point groups and cut directions. Theoretically, the d36 coefficient vanishes in piezoelectric ceramics because of its transversally isotropic symmetry. In this work, we modified the symmetry of poled PZT ceramics from transversally isotropic to orthogonal through ferroelastic domain switching by applying a high lateral stress along the “2” direction and holding the stress for several hours. After removing the compression, the piezoelectric coefficient d31 is found much larger than d32. Then, by cutting the compressed sample along the Zxt±45° direction, we realized d36 coefficients up to 206pC/N, which is measured by using a modified d33 meter. The obtained large d36 coefficients in PZT ceramics could be very promising for face-shear mode resonators and shear horizontal wave generation in nondestructive testing.