Coercive Field Ec Research Articles

Effect of substitution of (NiNb)4+ into B-sites on the phase formation, microstructure and electrical properties of Bi0.47Na0.47Ba0.06TiO3 ceramics

Bi0.47Na0.47Ba0.06Ti1-x(Ni1/3Nb2/3)xO3 ceramics (abbreviated as BNBT1-x(NN)x, x = 0, 0.01, 0.03 and 0.05) were synthesized by solid-state combustion. The effect of x on the phase formation, microstructure and electrical properties of BNBT1-x(NN)x ceramics was examined. The XRD pattern indicated the coexistence of rhombohedral and tetragonal phases in all the specimens. Moreover, Rietveld refinement confirmed that the tetragonal phase increased from 47 to 71% when x increased from 0 to 0.05. The morphology of BNBT1-x(NN)x ceramics was observed by SEM and the ceramics grains showed polygonal shapes and the grain growth tended to be anisotropic. With (NiNb)4+ substitution, the average grain sized decreased rapidly from 1.7 to 1.0 µm and the grain size distribution was narrower as the amount of (NiNb)4+ increased. The density, remnant polarization (Pr) and coercive field (Ec) rapidly decreased with increasing x. A significant decrease in the ferroelectric properties was caused by the increasing tetragonal phase.

Structural, Dielectric and Ferroelectric Characterizations of Sol-gel Prepared Ba1-xSrxTiO3 Nanoceramics

Ba1-xSrxTiO3 (0.0 ≤ x ≤ 0.5) nanoceramics were synthesized via sol-gel route and the structural and electric properties of the resulting compositions were investigated. revealed A tetragonal crystal structures for x = 0.0 - 0.3 and a cubic structure for x = 0.5 compositions was revealed by X-ray diffraction. The smaller ionic radii of Sr ions resulted in the lowering of c/a ratio with increasing x and a tetragonal to cubic structural transformation was observed at around x = 0.4. The average crystallite size gradually decreased with increasing x from 0 to 0.5. This trend was visible in electron micrographs. The room temperature dielectric constant in these nanoceramics increases with increasing Sr and a maximum value of 1553 was observed for x=0.3. Curie temperature (Tc ) of 125 °C was obtained for x=0.0, which shifted toward lower temperature with increasing x value. The value of Tc was observed as 100 and 75 °C for x = 0.1 and 0.3, respectively. The remnant polarization (Pr ), saturation polarization (Ps ), and coercive field (Ec ) decreased with increasing Sr concentration in BT due to the structural modifications. Value of Pr decreases from 0.637 to 0.229 μC/cm2, Ps decreases from 8.910 to 3.238 μC/cm2 and Ec decreases from 0.631 to 0.255 kV/cm with increasing x from 0 to 0.5.

Growth and electrical properties of Yb3+ A-site doped PMNT:Yb single crystal

0.01Yb2O3-0.69 Pb(Mg1/3Nb2/3)O3-0.30PbTiO3 (PMNT:Yb) single crystal with the size of Ø25 × 90 mm2 was successfully grown by the seed-guided Bridgman method. The electrical properties such as dielectric behavior, piezoelectric coefficient and ferroelectric properties were systematically characterized. The optimal d33 reached 2670 pC/N under the alternating current polarization conditions of 15 Hz, 14 kV/cm and 10 cycles. The crystal structure changed from the rhombohedral phase to the tetragonal phase during the growth process, and the phase transition temperature is 95 °C-100 °C, and TC is 128 °C-135 °C. Under the electric field of 20 kV/cm and frequency of 15 Hz, the coercive field EC of the crystal is 3.7 kV/cm, and the residual polarization Pr is 26.4 μC/cm2. Under alternating current polarization mode, the ferroelectric domain becomes periodically dense and regular, and the size of electric domain is uniform. In the wavelength range of 200–2000 nm, the absorption edge of PMNT:Yb crystal is 400 nm, and the wafer transmittance under unpolarized mode, direct current polarization mode and alternating current polarization mode are 41%–45%, 55%–58%, and 58%–63%, respectively. The PT-based relaxor ferroelectric crystals have great potential in the application of acoustic optical-electrical multifunctional couplers.

Fabrication of a lead-free ternary ceramic system for high energy storage applications in dielectric capacitors.

The importance of electroceramics is well-recognized in applications of high energy storage density of dielectric ceramic capacitors. Despite the excellent properties, lead-free alternatives are highly desirous owing to their environmental friendliness for energy storage applications. Herein, we provide a facile synthesis of lead-free ferroelectric ceramic perovskite material demonstrating enhanced energy storage density. The ceramic material with a series of composition (1-z) (0.94Na0.5Bi0.5TiO3-0.06BaTiO3)-zNd0.33NbO3, denoted as NBT-BT-zNN, where, z = 0.00, 0.02, 0.04, 0.06, and 0.08 are synthesized by the conventional solid-state mix oxide route. Microphases, microstructures, and energy storage characteristics of the as-synthesized ceramic compositions were determined by advanced ceramic techniques. Powder X-ray diffraction analysis reveals pure single perovskite phases for z = 0 and 0.02, and secondary phases of Bi2Ti2O7 appeared for z = 0.04 and 0.08. Furthermore, scanning electron microscopy analysis demonstrates packed-shaped microstructures with a reduced grain size for these ceramic compositions. The coercive field (Ec) and remnant polarization (Pr) deduced from polarization vs. electric field hysteresis loops determined using an LCR meter demonstrate decreasing trends with the increasing z content for each composition. Consequently, the maximum energy storage density of 3.2J/cm3, the recoverable stored energy of 2.01J/cm3, and the efficiency of 62.5% were obtained for the z content of 2mol% at an applied electric field of 250kV/cm. This work demonstrates important development in ceramic perovskite for high power energy storage density and efficiency in dielectric capacitors in high-temperature environments. The aforementioned method makes it feasible to modify a binary ceramic composition into a ternary system with highly enhanced energy storage characteristics by incorporating rare earth metals with transition metal oxides in appropriate proportions.

Development of energy harvesting and ferroelectric characteristic of thulium doped ZnO via graphene addition

Wet chemical co-precipitation and hydrothermal techniques were used to synthesize Tm-doped GO/ZnO (1:7) nanocomposites. Carbon concentration was found to be different in the prepared Tm-doped GO/ZnO powders. Both thulium doping and the addition of graphene oxide have affected dielectric, ferroelectric and piezoelectric properties of ZnO. The largest value of energy harvesting performance, namely (95 V, 2.40 μAcm−2), was obtained by the piezoelectric nanogenerator of Tm-doped GO/ZnO nanocomposite synthesized by hydrothermal method. The highest remnant polarization (Pr) and the lowest coercive field (Ec) namely (13.15 μC/cm2 and 4.25 kV/cm) were achieved by Tm-doped GO/ZnO nanocomposite synthesized by co-precipitation method. The achievements of present work make Tm-doped GO/ZnO hybrids promising candidates for designing self-powered sensors, energy harvesters and broad-temperature ferroelectric based memory devices.

Structural, microstructural, dielectric and ferroelectric properties of Ho3+ doped SrBi4Ti4O15 ceramics

The present work investigates microstructural, structural, ferroelectric and dielectric properties of Holmium, Ho3+, doped SrBi4Ti4O15 (SBT). Polycrystalline ceramics (SrBi4-xHoxTi4O15 SBHT, where x = 0, 0.02. and 0.03) were prepared by solid-state reaction method using high energy planetary ball mill. The surface morphology of all samples displayed dense microstructure and average grain size decreased with Holmium content increase. The XRD results of samples confirmed a single phase of SBT with orthorhombic crystal structure and a reduction in unit cell volume with the substitution of Holmium at B-site. The improvement in the structural and microstructural properties greatly enhanced the electric properties of SBHT. SBHT (x = 0.02) sample showed the improved ferroelectric properties (remnant polarization Pr = 1.63 μC/cm2 and Coercive field Ec = 0.51 kV/cm) making them suitable for ferroelectric applications. High Curie temperature (TC = 626 °C), elevated dielectric constant (εr = 236) and low loss (tanδ = 0.062) are obtained with the substitution of Ho (for x = 0.03) at B- site of SBT. These ceramics have high TC and improved thermal stability which makes these apt for the applications in high temperature sensors.

Structural and electrical properties of bismuth sodium titanate ceramic

Single-phase lead-free Bi0.5Na0.5TiO3 (BNT) perovskite ferroelectric ceramic was produced using a solid-state reaction method. A detailed investigation of the structural and electrical properties of BNT ceramic is conferred. According to phase analysis employing Rietveld refined X-Ray diffraction, the crystal structure is single phase with rhombohedral (R3C) symmetry. Raman spectra measurement also confirms the rhombohedral structure of BNT by originating numerous peaks from the TiO6 octahedron. The ferroelectric character of the BNT sample was established by a hysteresis loop measurement of polarisation vs electric field (P-E). The remnant polarisation (Pr) and coercive field (Ec) have characteristic values of 1.63 μC/cm2 and 29.91 kV/cm, respectively. The ferroelectric phase change is seen in the temperature-dependent dielectric research, with a transition temperature of 323°C. The compound possessed a low value of tanδ even at a high temperature (500°C) at 1 MHz. The prepared sample exhibited excellent dielectric characteristics from room temperature to high temperatures, making it ideal for various applications.

Electric and Magnetic Properties of Bi0.80Ba0.20FeO3‐Doped Ba0.85Ca0.15Ti0.90Zr0.10O3 Ceramics Prepared via the Solid‐State Combustion Technique

Lead‐free (1−x)Ba0.85Ca0.15Ti0.90Zr0.10O3–xBi0.80Ba0.20FeO3 [(1−x)BCTZ–xBBF] ceramics, with BBF content (x) between 0 and 0.4, are prepared via the solid‐state combustion technique. The effect of BBF content on the phase formation, microstructure, and electric and magnetic properties of BCTZ is studied. From the Rietveld refinement analysis, the BCTZ ceramic shows coexisting orthorhombic and tetragonal phases, with a ratio of 35.4:64.6 and the percentage of the tetragonal phase continuously increases when x increases from 0.02 to 0.1, and becomes purely tetragonal at x ≥ 0.2. When x increases, the average grain size, density, and relative density continuously decrease while the unit cell volume enlarges. The dielectric constant at room temperature (εR) tends to decrease while the dielectric loss at room temperature (tan δR) increases with increased BBF content. For x = 0, a pure BCTZ ceramic, a well‐saturated P–E loop is observed with a polarization (Pr) and coercive field (Ec) of 8.94 μC cm−2 and 4.06 kV cm−1, respectively. The ferroelectricity drastically decreases with x = 0.02. For x ≥ 0.06, the leakage current increases, which suppresses the ferroelectricity. With no BBF content (x = 0), the ceramic has diamagnetic properties that change to paramagnetic properties with x = 0.02–0.06 and finally to ferromagnetic properties when the BBF increases between 0.10 and 0.40. For x = 0.10–0.40, the remnant magnetization (Mr) continuously increases.

Effects of Ba2+doping on microstructure and properties of PLMNT electro-optic ceramics fabricated by hot-pressed sintering process

A series of highly transparent electro-optic (EO) ceramics Pb0.975-xBaxLa0.025(Mg1/4Nb1/2Ti1/4)0.99375O3 with the Ba2+ content of 0, 0.005, 0.01, 0.02, 0.04 were fabricated through the vacuum/oxygen hot-press sintering process. The effects of the barium substitution on the material phase transition, transmittance, dielectric, ferroelectric and electro-optic properties have been investigated and analyzed. With the Ba2+ content increasing, the shape of the ferroelectric hysteresis loop changed from rectangular to slim, the values of remnant polarization (Pr) and coercive electric field (Ec) decreased obviously. The maximum reduction of Pr can reach up to ∼89.8%. All the samples present the high transparency of ∼68% in the near infrared wavelength. The quadratic EO coefficients declines slightly while the Ba2+ content increasing. When the x is 0.01, the sample shows a relatively larger quadratic EO coefficient of ∼30.42 × 10−16 (m/V)2 and a lower Pr value of ∼2.08 μC/cm2, which promise the material a hopeful application in EO modulator.

Large electric-field induced strain in new ternary lead-free piezoelectric solid solution Na0.5Bi0.5TiO3-BaTiO3-Sr (Ta0.5Al0.5) O3

Ternary lead-free piezoelectric ceramics Na0.5Bi0.5TiO3-BaTiO3-Sr(Ta0.5Al0.5)O3 were synthesized via conventional solid-phase synthesis. All samples exhibited pure perovskite structure, indicating that Sr(Ta0.5Al0.5)O3 can be solidified into the Na0.5Bi0.5TiO3-BaTiO3 perovskite structure. The remanent polarization Pr and coercive field EC of the undoped Na0.5Bi0.5TiO3-BaTiO3 ceramic were Pr∼35.23µC/cm2 and EC∼42.46 kV/cm, respectively. The introduction of Sr(Ta0.5Al0.5)O3 sharply affected the ferroelectric properties of the substrate Na0.5Bi0.5TiO3-BaTiO3 ceramics. Increase in the content of Sr(Ta0.5Al0.5)O3 induces transition of this ternary system from a ferroelectric phase to an antiferroelectric-like phase, accompanied by double hysteresis loops in the 0.003SAT, 0.005SAT, and 0.01SAT components. The high dielectric constant ε′∼4300 was obtained for the 0.005SAT composition. The 0.015SAT composition yielded the maximum bipolar electric-field strain S (%) ∼0.53 % and high-field piezoelectric strain coefficient d33*∼ 996 pm/V. This result shows that a ternary Na0.5Bi0.5TiO3-BaTiO3-Sr(Ta0.5Al0.5)O3 solid solution is a promising alternative to lead-based piezoelectric materials in the field of high-performance actuators.

Improved energy storage in antiferroelectric AgNbO3-modulated 0.925Bi0.5Na0.5TiO3 – 0.075BaTiO3 relaxor ferroelectric ceramics

In this report, antiferroelectric AgNbO3-modified (1-x)(0.925Bi0.5Na0.5TiO3-0.075BaTiO3)-xAgNbO3 (x = 0–0.2) relaxor-ferroelectric ceramics were studied to optimize energy density and storage efficiency. Dielectric properties and microstructure were analyzed to explore the influence of antiferroelectric AgNbO3 (AN) in energy-storage performance of 0.925Bi0.5Na0.5TiO3-0.075BaTiO3 (BNBT) ceramics. By substituting proper AN concentrations (x ≤ 0.15), dielectric breakdown strength (BDS) can be effectively increased, while remanent polarization (Pr) and coercive field (Ec) were evidently reduced. The optimal recoverable energy density (Wrec) of 3.92 J/cm3 and storage efficiency (η) of 70% are respectively achieved for x = 0.1 (at E = 180 kV/cm) and x = 0.05 (at E = 110 kV/cm). Temperature-dependent dielectric permittivities show that 0.1∼0.15 AN-doped BNBT ceramics maintain low dielectric losses (tan δ < 0.1%) with a stable temperature coefficient of capacitance (TCC), which meets the X7R specification. This work demonstrates that antiferroelectric AN-doped BNBT relaxor-ferroelectric ceramics are suitable for using in high-density energy storage.

Self-powered, high sensitivity printed e-tattoo sensor for unobtrusive arterial pulse wave monitoring

Self-powered, highly unobtrusive, low-cost and accurate arterial pulse wave monitoring devices need to be developed to enable cost-efficient monitoring of entire cardiovascular disease risk groups. We report the development of a scalable fabrication process for a highly unobtrusive piezoelectric ultra-thin (t ~ 4,2 µm) e-tattoo arterial pulse wave sensor which utilizes only transparent and biocompatible polymer-based materials. The ferroelectric performance of the ultra-thin P(VDF-TrFE) material layer is optimized through the use of crosslinked PEDOT:PSS electrodes; this results in ~70 % and ~34 % improvements in remanent polarization (Pr) and coercive field (Ec), respectively, when compared to the sensors with pristine PEDOT:PSS electrodes. The ultra-thin form factor enables access to the high bending mode sensitivity of the P(VDF-TrFE) material layer; the maximum sensitivity value achieved in uniaxial and multiaxial bending is ~1700 pC N-1, which is ~50 times higher than the measured normal mode sensitivity. The increased sensitivity is linked to a specific set of direct piezoelectric coefficients using combination of experimental results, statistical analysis and finite element modeling. Finally, the accuracy of the e-tattoo sensor is demonstrated in the non-invasive measurement of radial artery pulse wave by comparing the signal to that obtained with reference device from 7 study subjects.

Effect of Crystal Structure and Phase on the Dielectric, Ferroelectric, and Piezoelectric Properties of Ca2+- and Zr4+-Substituted Barium Titanate

Barium titanate (BaTiO3) and its associate ternary metal oxide systems constitute versatile materials with immense potential for various technological applications in electronics and optoelectronics. Herein, we report on the synthesis and property optimization of lead-free ceramic samples, namely BaTiO3 (BT), BaZr0.2Ti0.8O3 (BZT), Ba0.7Ca0.3TiO3 (BCT), and BaZr0.2Ti0.8O3–0.5 Ba0.7Ca0.3TiO3 (BZT–BCT) composites. All of these materials were synthesized by the standard solid-state chemical reaction method, where tuning the composition and the crystal structure yields materials suitable for multifaceted applications related to capacitors, memory storage, and high-energy switching and transducers. Structural studies carried out using X-ray diffraction and Raman spectroscopy confirm the tetragonal phase for BT, BZT, and BZT–BCT samples, whereas BCT is a biphasic crystal system, which contains a small amount of the CaTiO3 phase. Scanning electron microscopy characterization of the surface morphology indicates the granular-dense microstructures of all of the samples. Energy dispersive spectroscopy confirms the high degree of purity and chemical homogeneity of the synthesized samples in addition to a well-maintained composition. Density measurements using Archimedes principles show that all of the samples have densities above 4.96 g/cm3. All of these materials exhibit typical polarization–electric field (P–E) hysteresis and field-induced strain butterfly (S–E) loops, which confirm their ferroelectric and piezoelectric nature. The frequency response of the dielectric constant shows a maximum dielectric constant of 2441 for pure BT and it decreases for higher frequencies, above 0.1 MHz. The dielectric properties of BT imply significant prospects for its future capacitor applications. Ferroelectric measurements, which are established by measuring the P–E hysteresis loop at 300 K, show that the BCT samples exhibit a 0.50 squareness ratio. The detailed analyses indicate that BCT is a candidate material for permanent memory storage device (FeRAM) applications, whereas BZT is good for switching applications. Furthermore, a moderately higher remnant polarization (Pr = 10.81 μC/cm2) is obtained for BT and a lower coercive field (Ec = 0.78 kV/cm) is obtained for the BZT sample. Also, piezoelectric coefficient and strain measurements show that BT has a piezoelectric coefficient of 183 ± 1 pC/N and a converse piezoelectric coefficient of 365.7 ± 2 pm/V, which are the highest values. The Q-factor for the BZT–BCT composite was observed to be 4.16 × 10–4 (cm2/μC)2, which is maximum, implying that BZT–BCT is suitable for energy conversion transducer applications. In this work, we comprehensively elucidate and discuss the properties and potential applications of BT and its associated ternary metal oxide systems.

Phase evolution and enhanced electrical properties in Ba0.85Ca0.15Zr0.10Ti0.90O3 lead-free ceramics prepared at different sintering temperatures

ABSTRACT Ba0.85Ca0.15Zr0.10Ti0.90O3 (BCZT) lead-free ceramics were prepared by sol–gel technique, and the influence of sintering temperature on phase evolution and electrical properties has been investigated. The X-ray diffraction patterns indicated that the BCZT ceramics sintered at 850°C do not well crystallized into perovskite phase and orthorhombic-tetragonal biphase coexists at higher sintering temperatures (1250–1350°C). The average grain size increases from 0.23 to 1.37 μm as the sintering temperature increases from 850 to 1400°C. The dielectric properties improve with increasing sintering temperature up to 1300°C. The BCZT ceramics sintered at 1300°C exhibit enhanced dielectric, ferroelectric and piezoelectric properties with high dielectric constant ϵ′ ∼ 3470, low loss tangent (tanδ) of 0.053, spontaneous polarization Ps ∼ 12 μC/cm2, remnant polarization Pr ∼ 2.35 μC/cm2 and coercive field Ec ∼ 1.13 kV/cm and high d 33 ∼ 367 pCN−1 while simultaneously maintaining a high Tc above 100°C.

High piezoelectricity in PFN–PNN–PZT quaternary ceramics achieved via composition optimization near morphotropic phase boundary

To analyze the effect of PFN content on the microstructure and electrical properties of xPb(Fe0.5Nb0.5)O3–(0.57−x)Pb(Ni1/3Nb2/3)O3–0.43Pb(Zr0.3Ti0.7)O3, the doping of xPFN–PNN–PZT) were systematically studied with 0.015 ≤ x ≤ 0.075. XRD patterns and Raman spectra analysis reveal that PFN diffuses into PNN–PZT perovskite lattice and forms new quaternary solid solution. With the increase of PFN content x, the proportion of rhombohedral (R) phase decreases gradually, whereas the proportion of tetragonal (T) phase displays a contrary trend. In particular, R–T coexistence near MPB was observed at x = 0.045. Meanwhile, optimized electrical properties of d33 = 961 pC/N, kp = 0.716, εr = 6298, and tanδ = 3.1% are achieved for the 0.045PFN–PNN–PZT ceramics. Moreover, the ceramics at MPB showed larger remnant polarization Pr = 24.55 μC/cm2, smaller coercive field Ec = 0.36 kV/mm, and lower dielectric relaxor degree γ = 1.813. All these results reveal that the enhanced electrical properties could be attributed to synergistic phase boundary motion, dielectric relaxor behavior and ferroelectric hysteresis effect.

Piezoelectric performance of 0.5BaZr0.2Ti0.8O3-0.5Ba1-xCaxTiO3 at triple phase point

0.5BaZr0.2Ti0.8O3-0.5Ba1-xCaxTiO3 ceramic samples with x = 15–35% have been fabricated to investigate the composition-driven phase evolution, ferroelectric, and piezoelectric properties. X-ray diffraction and temperature-dependent permittivity studies reveal the structural phase transition from the rhombohedral (R) to R + orthorhombic (O) and then O + tetragonal (T) having a tricritical triple phase points consisting of the R + O + T at x = 29.6%. The average grain size tends to increase with x but there is an exception of reducing grain size for x = 29.6%. The triple phase point displays the outstanding properties, such as minimum relaxation time (τ = 6.4 ms), large piezoelectric response (d33 = 543 pC/N), high saturation polarization (PS = 16.5 μC/cm2), small coercive field (Ec = 0.6 kV/cm), and high dielectric permittivity, over 8700 peaking at 21,765. These parameters reduce drastically at the O/R and O/T phase boundaries. Our studies indicate the important role of multiphase coexistence for enhancing the piezoelectric properties.

Effects of post cooling on the remnant polarization and coercive field characteristics of atomic layer deposited Al-doped HfO2 thin films

A study was conducted on how the cooling rate after the phase change heat treatment required to secure the ferroelectric (FE) properties affects the ferroelectricity of Al-doped HfO2 (Al:HfO2) thin films. When cooling the thin film to room temperature after heat treatment, the cooling rate was controlled through slow chamber cooling, which maintains and cools the sample inside the heat treatment equipment, slightly faster air cooling, and rapid cooling using deionized water. We achieved the dramatic increase of remnant polarization (Pr) and coercive electric field (Ec) using rapid quenching after phase change heat treatment. The 2Pr and 2Ec values of rapid quenched FE Al:HfO2 thin film are approximately ∼100 μC/cm2 and ∼9.5 MV/cm, respectively, which are the highest records among HfO2-based FE thin films reported so far. These significant improvements are attributed to inducing homogeneously distributed defects complexes and higher stress/confinement strain within Al:HfO2 thin film, leading to preventing pinched hysteresis loop and stabilize orthorhombic crystal structure. Furthermore, endurance up to 2 × 106 cycles and reasonable projected 10 years retention properties were achieved, stably without wake-up and fatigue in quenched FE Al:HfO2 capacitor. These results propose a beneficial method to improve the ferroelectricity of HfO2-based thin films.

The effect of domain switching on the lattice symmetry and dielectric properties of (Bi0.5Na0.3K0.2)TiO3–0.2SrTiO3-(Ba0.8Ca0.2)TiO3 piezo-ceramic by poling field

The present study illustrates the effect of domain switching on the structural, dielectric, and piezoelectric properties of [0.75(Bi0.5Na0.3K0.2)Ti O3-0.2SrTi O3-0.05(Ba0.8Ca0.2)Ti O3] (i.e., BNKT- ST-BCT) Pb-free ceramic caused by poling effect. The sample has been synthesized by the solid reaction technique. The poling conditions were changed from (10–50 kV/cm) for 30 min at 100 °C. The pristine ceramic sample showed pseudo-cubic crystal structure, while tetragonal structure was detected for all the poled samples. The pristine sample showed a normal ferroelectric loop with a low coercive field (Ec =12 kV/cm) owing to the domain grow caused by domain wall displacement. The effect of poling field into Raman spectra showed variation the volume fraction of orthorhombic and tetragonal phases. Increasing the intensity of the tetragonal phase is related to the increase in lattice symmetry of the poled samples at a high poling field. Relaxor to paraelectric phase transition was observed at Burn's temperature (TB) of the un-poled sample, while the poled rates undergo a ferroelectric to relaxor phase transition at depolarization temperature (Td). In the regime of the sub-switching domain, the maximum permittivity was found to increase by poling field due to Rayleigh effect, while at high poling field it was observed to decrease due to tunability effect. The maximum current peak of relaxor to ferroelectric phase transition was observed to mitigate by increasing the poling effect. The converse piezoelectric coefficient, (d33∗) was achieved to be higher in the un-poled sample due to the lowest crystal symmetry in the absence of a poling effect. The existence of poling process leads to shrink both current peak and (d33∗) values, indicating the dominated of the tetragonal phase rather than the orthorhombic phase. Such results offer distinct features of an un-poled ceramic sample that make it suitable for different technological applications such as energy storage devices, sensors, and actuators.

Electrocaloric effect and temperature dependent scaling behaviour of dynamic ferroelectric hysteresis studies on modified BTO

The large electrocaloric effect associated with the ferroelectric-relaxor and ferroelectric-paraelectric phase transition, and various temperature dependent scaling behaviours on A-site modified BaTiO3 (Ba1-xSrxTiO3, x = 0.00, 0.10, 0.20, and 0.25) have been reported in this article. The compositionally induced relaxor behaviour with diffuse phase transition has been reported. The Rietveld refinement of XRD patterns reveals that all the samples crystallize to the P4mm space group. Raman spectra analysis at room temperature supports the XRD patterns analysis. The diffuse phase transition behaviour of the prepared sample has been confirmed by estimating the diffuse phase parameter (γ = 1.444 ± 0.003) from the temperature variation dielectric plot. A large adiabatic temperature change (ΔT) of 0.278 K and isothermal entropy change (ΔS) of 0.494 J/kgK have been observed for the sample x = 0.20 (Ba0.8Sr0.2TiO3) at 338 K. The temperature dependent scaling relation for remnant polarization (Pr), coercive field (Ec), and hysteresis area <A> are found to be Pr∝T−1.009,Ec∝T−1.890 and <A>∝T−1.169, respectively. The present comprehensive studies on A-site modified BaTiO3 illustrate the electrocaloric cooling efficiency of this material.

Ferroelectric properties and large electric field-induced strain of Eu3+-doped Na0.5Bi0.5TiO3–BaTiO3 lead-free ceramics

Eu3+-doped lead-free piezoelectric ceramics, 0.937Na0.5Bi0.5−xEuxTiO3-0.063BaTiO3 (abbreviated as NBExT-BT, where x = 0, 0.003, 0.005, 0.01, 0.013, 0.015, 0.017, and 0.02), were synthesized using a conventional solid-state synthesis method. All the component samples were crystallized in a pure perovskite structure without a secondary phase. The introduction of Eu3+ caused the evident variation of the dielectric, ferroelectric and luminescence properties. The remanent polarization and coercive field of the pure NBT-BT are Pr ∼29.24 μC/cm2, Ec∼39.33 kV/cm, respectively. The maximum of the remanent polarization Pr of ∼38.02 μC/cm2 at room temperature and the highest dielectric constant of 6899 with a frequency of 1 kHz were obtained for NBE0.003T-BT. The maximum bipolar strain Smax of ∼0.91% and the minimum of coercive field Ec ∼18.45 kV/cm were achieved by the NBE0.015T-BT, resulting from the formation of a double hysteresis loop. For all the components, Eu3+ doping stabilized the antiferroelectric phenomenon at high temperature. Furthermore, the polarized NBE0.015T-BT had the strongest fluorescence luminescence intensity as well as a fluorescence lifetime reaching 785.98 μs.