Lead-free Ba0 Research Articles

Composition Dependent Structural and Electrical Properties of (Ba0.9-zSrzCa0.1)(Zr0.1Ti0.9)O3, (0.08 ≤ z ≤ 0.12) Ceramics

Pellet samples of (Ba0.9−zSrzCa0.1)(Zr0.1Ti0.9)O3, with z ranging from 0.08 to 0.12, were prepared using the solid-state reaction route. Dielectric measurements were obtained for all the prepared compositions at various frequencies (1–1000 kHz) and temperatures (room temperature to 250 °C). The structural and piezoelectric properties were obtained at room temperature (RT), where maximum dielectric (5615 at 1 MHz) and piezoelectric constant (964 pm V−1) were observed for the samples with z = 0.10 among the prepared samples. Further, for z = 0.10, the X-ray diffraction (XRD) peak patterns showed an anomalous peak shifting phenomenon followed by an irregular shift in the c/a vs z plot’s slope. In addition, maximum grain size and density were observed for z = 0.10. The obtained maximum values of dielectric constant (ε), piezoelectric constant (d33*), break in XRD peak shifting patterns, and a minimum in c/a ratio of the prepared samples show significant composition-dependent electrical and structural properties indicating morphotropic-phase boundary (MPB), near z = 0.10 among the prepared compositions. Thus, lead-free (Ba0.8Sr0.10Ca0.1)(Zr0.1Ti0.9)O3 system may be a suitable choice for various piezoelectric applications.

Optimization of Structural, Dielectric, and Electrical Properties in Lead-free Ba0.85Ca0.15Zr0.1Ti0.9O3 through site engineering for Biocompatible Energy Harvesting

Piezoelectric energy harvesting has recently gained attention due to its high power density and potential for self-powered sensor networks. This study investigates the effects of dopants on Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) ceramics, examining Strontium (Sr2+), Zinc (Zn2+), and praseodymium (Pr3+/4+) ions at different sites and their impact on structural, dielectric, and electrical properties. X-ray diffraction and Rietveld analysis reveal a coexistence of tetragonal and rhombohedral/orthorhombic phases, with a predominant tetragonal phase, confirmed by Raman analysis. Energy-dispersive X-ray spectroscopy ensures chemical homogeneity. The density measurements indicate a dense microstructure with a relative density of 90-95%. Dielectric analysis shows a relaxor-like behavior in AB-site doped BCZT ceramics, validated by polarization-electric field hysteresis loops. B-site doped BCZT ceramics exhibit ultra-low leakage currents, approximately 103 times lower than undoped BCZT. An optimized biocompatible flexible film-based energy harvester, incorporating A-site doped BCZT ceramic particles, demonstrated impressive energy harvesting capabilities. A simple finger tapping generated ~80.2V and ~18.2nA, with an average peak-to-peak power density of 7.6 µW-cm-3. These results highlight the significant potential of dopant inclusion in BCZT ceramics, marking a major advancement in doping strategies for piezoelectric energy harvesting in miniature electronics.

Electrocaloric, energy storage and dielectric properties of lead-free Ba0.85Ca0.15Zr0.1Ti0.9O3 ceramic prepared by hydrothermal-assisted sintering technique

Electrocaloric, energy storage and dielectric properties of lead-free Ba0.85Ca0.15Zr0.1Ti0.9O3 ceramic prepared by hydrothermal-assisted sintering technique

Effect of milling time on structural and electrical properties of thermomechanically synthesized of Ba0.1 (Bi0.45Na0.45)TiO3 nanoceramics for ferroelectric random-access memory device

Lead-free Ba0.1(Bi0.45Na0.45)TiO3 (BBNTO) nanoceramics were synthesized using high-energy ball milling, followed by a solid-state reaction method. XRD analysis of the microstructure indicated the formation of tetragonal symmetry. The crystallite size of the nanoceramic powder decreased from ∼ 28 nm to 10 nm after milling for 0, 30, 60, and 90 hours. The dielectric properties of the nanoceramics showed significant improvement, with a diffuse phase transition occurring around 80 °C). The dielectric constant increased with temperature across various frequencies, reached a maximum value at approximately at temperature ∼ 380 °C. At lower temperatures and higher frequencies, the relative permittivity and tangent loss depend on the crystallite size and milling duration. Impedance spectroscopy data analysis revealed size-dependent impedance characteristics and dielectric relaxation. The ac conductivity plot adhered to the Arrhenius relation, and the calculated activation energy confirmed the negative temperature coefficient of resistance (NTCR) behavior. P-E loops confirmed ferroelectric properties, indicating potential for use in future ferroelectric-based storage devices.

Low field assisted electrocaloric effect and energy storage responses through optimization of morphotropic phase boundary by sintering temperature for lead-free Ba0.95Ca0.05Sn0.09Ti0.91O3 ceramics

The development of lead-free ferroelectric materials is highly desired for next-generation energy storage and superior electrocaloric effect (ECE) applications. However, one of the significant challenges in lead-free dielectric materials is to obtain enhanced ECE and energy storage density at lower applied electric fields, needed for realization of sustainable and efficient energy solutions. Herein, the sol-gel elaborated lead-free Ba0.95Ca0.05Sn0.09Ti0.91O3 ceramics have been synthesized and sintered at temperatures 1100 and 1200 ˚C. The sample sintered at 1200 ˚C exhibits low field assisted improved ∆T ∼ 0.42 K and ∆S ∼ 0.52 J/kg/K values and are closely associated with presence of MPB and relaxor characteristics. The enhanced recoverable energy density (Wrec) and total energy density (Wtot) are also obtained as 79 mJ/cm3 and 87 mJ/cm3 for the same sample sintered at 1200 ˚C with excellent conversion efficiency of 91 % under a very low applied electric field of 30 kV/cm. The results demonstrate that the optimization of sintering temperature significantly affects the MPB evolution, microstructure and emergence of relaxor characteristics owing to vibrant polar-nano regions that result in enhanced ECE and energy storage characteristics. The present work would be beneficial for advancement of lead-free ferroelectric materials as an efficient electrocaloric cooling and sustainable green energy solutions.

Enhanced buoyancy and propulsion in 3D printed swimming micro-robots based on a hydrophobic nano-fibrillated cellulose aerogel and porous lead-free piezoelectric ceramics

This paper provides the first demonstration of additively manufactured swimming micro-robots which combine a hydrophobic nanofibrillated cellulose aerogel, to provide long-term buoyancy, with a low acoustic impedance porous piezoelectric ceramic for improved propulsion. The hydrophobic nanocellulose aerogel is shown to exhibit a high and stable contact angle that was maintained for extended periods of time, which facilitates long-term and stable buoyancy of the micro-robot. To quantify the benefits of introducing porosity into the active piezoelectric element, a new analysis model was developed to inform material design and maximize the acoustic propulsion force. Detailed characterisation and modelling of the swimming robots demonstrated that a swimming robot based on a lead-free porous Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) ceramic exhibited a higher acoustic radiation propulsion force and a faster swimming speed compared to a robot fabricated using a dense ceramic element. These benefits were associated with the lower elastic modulus, density and acoustic impedance of the porous piezoelectric material. The lower dielectric constant, reduced device capacitance, and lower resonant frequency of the porous piezoelectric element also significantly reduced the driving current and power requirements of the robot. This work therefore provides new insights on the impact of hydrophobic and acoustically matched piezoelectric materials on the performance of swimming micro-robots, and successfully demonstrates the use of porosity to improve acoustic impedance matching of resonant piezoelectric devices, such as micro-robots and ultrasonic transducers.

Structural, electrical, and dynamic scaling behavior of Ba0.85Ca0.15Zr0.10Ti0.90O3 nanoceramics synthesized at low temperature by sonochemical method

In contrast to lead-based materials, lead-free ceramics Ba0.85Ca0.15Zr0.10Ti0.90O3 (BCZT) offer outstanding dielectric, ferroelectric, and piezoelectric properties. A novel sonochemical method is employed to synthesize BCZT at low temperatures. The impact of high-energy acoustic waves reduces the calcination temperature to 600 °C, which is 300–400 °C lower than the already reported values. The samples are further sintered at different temperatures. The BCZT shows good dielectric properties (εr ∼3000 and tanδ ∼0.075 at 1 kHz) at room temperature. X-ray diffraction analysis shows the co-existence of tetragonal and orthorhombic phases. Further, the scaling behavior is studied for domain dynamics in the sample. A three-stage polarization reversal mechanism is observed in BCZT ceramics. From the systematic study of the domain reversal mechanism, BCZT appears to be a promising candidate for sensors and actuator applications.

Energy storage efficiency and electrocaloric performances in lead-free Ba0.87Ca0.13(Ti0.9Zr0.1)0.98(Zn1/3Nb2/3)0.02O3 ceramic

Ba0.87Ca0.13(Ti0.9Zr0.1)0.98(Zn1/3Nb2/3)0.02O3 ceramic was prepared using a solid-state reaction method. This work investigates their dielectric, ferroelectric, energy storage, and electrocaloric properties. X-ray diffraction analysis confirms a pure perovskite structure. The dielectric constant reaches a maximum of 9364 at 326 K. Enhanced total energy density, recovered energy density, and energy storage efficiency are observed between 303 K and 363 K. Artificial neural networks (ANNs) are employed for the indirect determination of large ECE and responsivity based solely on measured ferroelectric polarization (P(E,T)). This approach offers rapid and accurate predictions with minimal experimental data, significantly accelerating the characterization of novel electrocaloric materials. The maximum ECE occurs above the Curie temperature (TC) and increases with higher electric fields. The ceramic exhibits significant ECE parameters around TC with a broad electrocaloric temperature span. Various figures of merit, including relative cooling power, refrigerant capacity, and temperature-averaged entropy change, are explored under different electric fields, demonstrating the material's potential for green cooling devices. These figures improve monotonically with increasing field strength. A comprehensive analysis of the field dependence of ΔS (entropy change) confirms the second-order nature of the electric phase transition through master curve analysis. In conclusion, these lead-free ceramics exhibit promising applications in high-performance energy storage devices and solid-state refrigeration technology.

Morphotropic phase boundary evolution with synergistic effect of sintering temperature to improve electrocaloric and energy storage performances of lead-free Ba0.95Ca0.05Sn0.09Ti0.91O3 (BCST) ceramic

The designing of lead-free ferroelectric ceramics for application in environment-friendly efficient electrocaloric cooling and energy storage devices is still challenging and need to be considered. A major challenge, however, is how to simultaneously achieve higher polarization and low hysteresis loss at low applied electric field. In this perspective, we comprehensively investigated sol-gel derived Ba0.95Ca0.05Sn0.09Ti0.91O3 (BCST) ceramics by varying the sintering temperature to explore its electrocaloric and energy storage capabilities. The excellent ∆T ∼ 1.03 K, ∆S ∼ 1.32 J/kg.K and high electrocaloric responsivity ΔT/ΔE ∼ 0.34 K.mm/kV at very low applied electric field of 30 kV/cm are obtained for pristine BCST sample sintered at 1400 °C. Additionally, we observed Wrec ∼ 136.18 mJ/cm3 and giant energy conversion efficiency η ∼ 94.29 % under very low applied electric field of 30 kV/cm for the same BCST sample. Our results reveal that control of sintering temperature contributes to a favorable and stable microstructure, including R-O-T phase coexistence and substitutional heterogeneity-induced nano-polar regions (PNRs) which strengthens the Polarization and supports the thin hysteresis loop. Thus all these factors simultaneously contributing to make BCST ceramic as a potential material for applications in advanced electrocaloric cooling and energy storage capacitors.

Enhanced dielectric and electrical properties of Ba(1−x)Nd2x∕3Zr0.1Ti0.9O3 (0.00 ≤ x ≤ 0.04) electroceramics for high temperature-based energy storage devices

The demand for high-temperature endurable dielectric materials with higher thermal stability in electronic systems operating under extreme temperatures sets a significant channel for the electronic industry. This work focuses on the dielectric and impedance behavior for lead-free Ba1−xNd2x∕3Zr0.1Ti0.9O3 (BNZT); (0.00 ≤x≤ 0.04) between 300 ∘C – 400 ∘C and synthesized by conventional solid-state reaction method at optimum temperatures. Structural characterizations confirmed the tetragonal (P4mm symmetry) structure formations for the BNZT ceramics. XPS analysis confirmed the Nd-substitution at the Ba-site in the BNZT ceramics. FE-SEM study showed grain growth reduction with enhanced grain boundaries. The dielectric study showed lower dielectric loss with enhanced dielectric permittivity at high temperatures. Impedance analysis confirmed the negative temperature coefficient of resistance (NTCR) and non-Debye type behavior with higher thermal stability. Singly-ionized oxygen vacancies mainly govern the conduction process in BNZT ceramics. Enhanced dielectric and impedance properties suggest that Nd-substituted BNZT electroceramics are promising materials for applications in high-temperature-based energy storage systems.

Structural, electronic and optical properties of complex lead-free ferroelectric Ba0.7Ca0.3TiO3 materials: A DFT study

Structural, electronic and optical properties of complex lead-free ferroelectric Ba0.7Ca0.3TiO3 materials: A DFT study

Effect of sintering condition and Ca2+-substitution on structural and electrical properties of lead-free Ba0.46Sr0.54TiO3 piezoceramics for uncooled IR detectors application

Effect of sintering condition and Ca2+-substitution on structural and electrical properties of lead-free Ba0.46Sr0.54TiO3 piezoceramics for uncooled IR detectors application

Large electrocaloric effect across the non-hysteretic electrostructural phase transition in lead-free (Ba0.88Ca0.12)(Ti0.94Sn0.06)O3 ceramics

Structural, dielectric, and electrocaloric properties were investigated in Pb-free ceramic (Ba0.88Ca0.12)(Ti0.94Sn0.06)O3 (BCST), synthesized using solid-state sintering method. Rietveld refinement of room temperature XRD data revealed the existence of pure perovskite tetragonal (P4mm) phase. Temperature-dependent XRD analyses confirmed a structural transition from tetragonal to cubic phase near 380 K. Temperature-dependent dielectric constant (εr) and specific heat capacity (Cp) confirmed the presence of thermal hysteresis in two phase transitions near 233 ± 10 K and 254 ± 10 K, and a non-hysteretic behavior at the Curie temperature (TC∼373 ± 10 K). A comprehensive Raman study corroborated the existence of phase transitions. Electrocaloric properties were determined using indirect method utilizing the non-hysteretic nature across TC. A large adiabatic temperature change of |∆T| = 0.52 K, isotropic entropy change |∆S| = 0.68 J/kg.K, electrocaloric coefficients, |∆T/∆E |= 0.311 K.mm/kV and |∆S/∆E| = 0.41 J.mm/K.kg.kV were obtained at 380 K for an electric field of 16.7 kV/cm. Obtained value of |∆T/∆E| is relatively good, reported among other BaTiO3-based ceramics.

Investigation of structural, morphological, dielectric, optical, and ferroelectric-energy storage properties of [(1-x) BCT-(x) BZT] electroceramics

Extensive research and advancements have been progressed by the vast potential of eco-friendly dielectric capacitors in high-level electronic elements and high-performance pulsed power systems thus far. Ferroelectric ceramic materials exhibiting relaxor properties and significant dielectric constants are prime candidates for attaining exceptional energy storage capabilities. Herein, a lead-free (1-x) Ba0.9Ca0.1TiO3–xBaZr0.15Ti0.85O3 (abbreviated as (1-x) BCT-xBZT) solid solution system has been synthesized via the conventional solid-state reaction technique, with varying levels of BZT doping. The X-ray diffraction study confirmed pure perovskite structure formation in the prepared ceramics, and the coexistence of orthorhombic (O) (space group- Amm2) and tetragonal (T) (space group-P4mm) phases has been detected through the Rietveld refinement technique at room temperature. Rietveld refinement data and associated analysis highlight the gradual shift of crystal symmetry from Amm2 to P4mm as the x content increases. Replacing BZT in Ca-modified BaTiO3 has led to significant enhancements in microstructural properties and an increase in the width of the optical band gap. This, in turn, enhances energy storage capabilities compared to pure BCT. Incorporating BZT into BCT has led to the evolution of relaxor ceramics, a crucial development for achieving elevated levels of recoverable energy storage density. In this study, the solid solution comprising 0.6BCT-0.4BZT exhibits distinct traits, including a diffuse phase transition, high breakdown strength, shallow dielectric loss (tanδ <0.007), and significantly high dielectric constant. Due to enhanced electrical characteristics, the 0.6BCT-0.4BZT possesses very high saturation polarization of ∼48 μCcm−2, a total energy density of 1.71 J/cm3, and a recoverable energy density of 1.1 J/cm3. In addition, the optimized ceramics demonstrate concurrent achievement of high-frequency stability (10–250 Hz), fatigue resistance (up to 104 cycles), and favorable temperature stability (20–160°C). This study showcased a potential material candidate suitable for energy storage devices functioning within low to medium-electric fields.

In situ electric field-dependent structural changes in (Ba,Ca)(Zr,Ti)O3 with varying grain size

The functional properties of piezoelectric ceramic materials, such as barium titanate, are highly dependent on grain size. Lead-free polycrystalline Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) samples were prepared with a combination of the hydrothermal method and spark plasma sintering to achieve grain sizes from 100 nm to 10 μm by varying the maximum sintering temperature. In this range, a transition from a nearly linear dielectric to a ferroelectric response can be seen in macroscopic electromechanical measurements, demonstrating the importance of grain size on functional properties in BCZT. Furthermore, in situ electric field-dependent synchrotron x-ray diffraction measurements were performed to quantify the intrinsic and extrinsic strain contributions and their variations with grain size. At lower grain sizes, the data revealed a significant loss of extrinsic contributions in the piezoelectric behavior, limiting the response to intrinsic contribution associated with lattice strain. For BCZT, a critical grain size between approximately 0.08 and 0.18 μm is proposed, below which no piezoelectric response was observed.

Electrical, ferroelectric and electro-caloric properties of lead-free Ba0.85Ca0.15Ti0.95(Nb0.5Yb0.5)0.05O3 multifunctional ceramic

In this study, lead-free Ba0.85Ca0.15Ti0.95(Nb0.5Yb0.5)0.05O3 (BC15TYN5) ceramic has been successfully obtained through the conventional solid-state reaction. It has been found the multifunctionality of the BC15TYN5 ceramic. It exhibits ferroelectric properties, with a significant remanent polarization value of about Pr = 9.36 μC/cm2, and a recoverable energy storage density value of about Wrec = 42.21 mJ/cm3. Additionally, it displays a dielectric permittivity of about ε′r = 7230 around TC = 80 °C, and an electro-caloric strength value of about ξ = 0.12 K mm/kV. It's worth noting that these values surpass those typically found in BaTiO3 ceramics elaborated with similar experimental conditions. Electrical study (impedance, modulus, and conductivity characteristics) is essential for characterizing the BC15TYN5 material, determining its suitability for various technological applications, and optimizing manufacturing processes. The Cole-Cole plots exhibited two relaxations associated with the contribution of the grains and grain boundaries. The relaxation times for both grains and grain boundaries showed temperature-dependent variation following Arrhenius relation. The measured AC conductivity was evaluated by applying the Jonsher power law. Based on the thermal evolution of the exponent S, it was confirmed that the conduction mechanism follows the Correlated Barrier Hopping (CBH) model. These properties make BC15TYN5 ceramic suitable for applications such as dielectric capacitors, ferroelectric random-access memories, electrical energy storage units, and electro-caloric refrigeration systems.

High energy storage performance of (1-x)Ba0.5Sr0.5TiO3-xK0.5Na0.5NbO3 ceramics via a combined strategy of fine grains and multiphase polar nanoregions

Electrostatic dielectric capacitors have received great attention due to their ultrafast charging-discharging speed and ultrahigh power density. However, the low energy storage density and efficiency are the main obstacles to their practical applications. In this work, solid solution relaxor ceramics with different proportions of lead-free ferroelectrics Ba0.5Sr0.5TiO3 (BST) and K0.5Na0.5NbO3 (KNN) were prepared. Superior energy storage performance was achieved in the 0.7BST-0.3KNN ceramics with a breakdown strength (Eb) of 510 kV/cm, a recoverable energy storage density (Wrec) of 4.10 J/cm3, and an energy storage efficiency (η) of 80 %, which was fairly stable over the temperature range of 30–100 °C. Since multiple cations with different valence and radius coexist on the equivalent sites (A or B sites) of the solid solutions, the chemical disorder and the corresponding lattice distortion induced the coexistence of cubic, tetragonal, and orthorhombic phases, as well as the appearance of the multiphase polar nanoregions (PNRs), making the ferroelectric hysteresis loops linear. At the same time, ultrafine grains in the ceramics greatly improved the Eb. For achieving excellent energy storage performance, this work demonstrates a potential candidate of (1-x)BST-xKNN lead-free solid solution ceramics and a combined strategy of fine grains and multiphase PNRs.

Impact of air and vacuum calcination on the properties of lead-free piezoelectric Ba0.85Ca0.15Zr0.1Ti0.9O3 ceramics for mechanical energy harvesting

Piezoelectric materials play a crucial role in energy harvesting applications, efficiently capturing renewable energy from sources like human activities and vibrations. Oxygen vacancies, common imperfections in these materials, significantly influence their overall effectiveness. In our study, Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) powder was calcined under different conditions (air and vacuum) to investigate their impact on crystal structure, microstructure, electrical properties, and energy harvesting performance. X-ray diffraction (XRD) and Rietveld analysis confirmed varied phases in vacuum calcined BCZT with a smaller particle size. X-ray photoelectron spectroscopy (XPS) revealed lower oxygen vacancy concentration for vacuum-calcined samples. The vacuum calcined BCZT ceramics demonstrated a remarkable 580% enhancement in the figure of merit (FOM) when contrasted with traditional ceramics, highlighting superior dielectric and piezoelectric characteristics. In mechanical energy harvesting, BCZT ceramics, protected by polyimide with Cu/Ag electrodes, outperformed conventional ceramics, generating a higher open-circuit voltage (10.61 V) and peak-to-peak power (1.510 mW/cm3). This energy harvester maintained stable output through 7000 cycles, suggesting its potential for powering miniature electronics.

A and B site engineered doping of the Bi2O3 to tune the structural and optical properties of lead-free BCZT ceramic

This work reports the different solid-state synthesis routes to tune between the A-site and B-site incorporation of the Bi2O3 additive element in the lead-free Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) ceramic. The structural and optical properties of the synthesized samples were systematically investigated by utilizing XRD, FT-IR spectroscopy, Raman Spectroscopy, UV–visible, and Photoluminescence spectroscopy. The shifting of the XRD peaks towards higher angles and the decrement of the O–Ba–O bond length in the FT-IR spectra of the doped sample confirmed the A-site incorporation of the Bi3+ ion. Whereas, B-site substituted samples have shown the lower angle shifting of the XRD peaks and increased value of the O–Ti–O bond length in FT-IR spectra. The presence of co-existing multi-phases in all prepared ceramics structures were verified by the splitting of XRD peaks and Raman Spectroscopy data analysis. A significant decrement in the value of the energy band gap and higher emission intensity for the A-site doped sample was observed from the UV–visible and PL spectra respectively. These observations made from the optical properties indicate that the A-site substituted ceramics can greatly enhance the electrical and optical properties of the pure material concerning the B-site substituted ceramics.

The mechanism of ferroelectric phase transformation in Gd2O3 modified BCZT ceramics: Experimental studies and first-principles calculations

Lead-free (Ba0.85Ca0.15)(Ti0.90Zr0.10)O3 (BCZT)-based piezoelectric ceramics have attracted considerable interest due to their excellent piezoelectric properties and abundant phase structures. However, there is a serious lack in the theoretical calculations for the ferroelectric phase transition behavior. Here, the experimental and first-principles calculations were utilized to analyze the ferroelectric phase transition process of (Ba0.85Ca0.15)(Ti0.90Zr0.10)O3-xGd2O3(BCZT-xGd, x = 0, 0.02, 0.04, and 0.05) ceramics. The incorporation of Gd2O3 has induced a transformation from tetragonal to rhombohedral phase due to the decrease in the dislocation energy with A-site cations and the attenuation of the bonding energy between B-site cations and the planar O atoms. Moreover, the hybridization between the d orbitals of B-site atoms and the O 2p orbitals, coupled with the reduction of the polarization vector along the [001] axis, leads to enhanced weak coupling relaxation. This work provides a theoretical basis for the ferroelectric phase transition behavior of other piezoelectric systems.