Ferrite Barium Titanate Research Articles

Cobalt Ferrite@Barium titanate core-shell nanoparticles empowered triboelectric electromagnetic coupled nanogenerator for self-powered electronics

In pursuing sustainable energy solutions for wearable technology and Internet of Things (IoT) devices, achieving high power in self-powered electronics is a significant challenge. This study introduces a novel hybrid nanogenerator by integrating a triboelectric nanogenerator (TENG) and an electromagnetic generator (EMG) to achieve both high voltage and high current outputs simultaneously. The cobalt ferrite barium titanate (CoFe2O4@ BaTiO3) core–shell nanoparticles (NPs) were chosen for their unique ability to enhance the system’s performance by combining triboelectric, piezoelectric, and electromagnetic properties. The BaTiO3 shell exhibited robust triboelectric and piezoelectric properties essential for TENG operation, while the CoFe2O4 core, influenced by the EMG’s magnetic field, induces additional static charges, significantly boosting overall energy conversion efficiency. The TENG and EMG in the combined system operate together in a contact-separation mode, where their in-phase output signals are seamlessly combined via a double bridge rectifier, resulting in a robust power output of 37.7 mW and a power density of 1.86 mW/cm2, with cycling stability of over 10,000 cycles. The uniquely designed TENG-EMG combined nanogenerator (C-TENG) exhibited striking adaptability, effectively operating across different low-to-high frequencies and load situations while constantly powering portable electronic devices. This innovative approach meets the high energy demands of modern self-powered electronics with exceptional efficiency, durability, and high-power density, positioning it as a versatile solution for wearable biomechanical energy harvesting.

Destruction of conducting channels driven resistivity enhancement in bismuth ferrite-barium titanate based ceramics

Bismuth ferrite-barium titanate (BF-BT) based ceramics have attracted extensive attention due to their high Curie temperature. However, the high conductivity and large leakage current greatly limit their high-temperature applications. Although manganese (Mn) was widely utilized in BF-BT ceramics to improve the resistivity, the increase extent is still limited. Inspired by the recently reported ferroelectric/relaxor composite piezoceramics with enhanced strain response, we are considering that composition inhomogeneous may also have an influence on resistivity. In this work, “two-step” method is used to prepare pseudo-composite ceramics in (1-x)[0.7BiFeO3-0.3BaTiO3]/x[(0.7BiFeO3-0.3BaTiO3):1.5 %Mn]. The combination of 0.7BF-0.3BT and (0.7BF-0.3BT):1.5 %Mn is not strictly a composite ceramic, but rather exhibits heterogeneous diffusion of Mn during high-temperature sintering, making it a solid solution with inhomogeneous composition distribution. The maximum resistivity (5.86×106 Ω•cm, at 300 ℃) can be achieved when x = 0.3, which is greatly improved compared to the conventionally processed (one-step method) samples containing the same average amount of MnO2 additive. The enhanced resistivity can be attributed to the inhomogeneous defect distribution induced by the heterogeneous diffusion of Mn, leading to the difficulty of defect carriers to form a conductive channel.

Broadband dielectric spectroscopy of Nb-doped 0.7BiFeO3–0.3BaTiO3 ceramics

Bismuth ferrite-barium titanate (BF-BT) solid solutions are lead-free ferroelectrics that show great promise as the basis for high temperature piezoelectric transducers. This article investigates the dielectric properties of such materials using broadband dielectric spectroscopy. The study focuses on the re-entrant relaxor ferroelectric behaviour of Nb-doped BF-BT ceramics, exploring a wide frequency range from approximately 20 Hz to 30 GHz and temperature from 200 to 500 K. The results reveal the presence of thermally induced transitions between ordered and disordered states. Quantitative analysis of the dielectric dispersion is accomplished using the Cole-Cole model, modified to account for the contribution from conduction losses at low frequencies/high temperatures. This analysis revealed that the freezing temperature of the polar nanoregions is around 158 K, with an activation energy of 0.194 eV. The findings contribute to understanding the dielectric relaxation mechanisms and thermal evolution of functional properties in BiFeO3-BaTiO3 ceramics.

Temperature-Dependent Ferroelectric Properties and Aging Behavior of Freeze-Cast Bismuth Ferrite-Barium Titanate Ceramics.

Lead-free BiFeO3-BaTiO3 (BF-BT) piezoceramics have sparked considerable interest in recent years due to their high piezoelectric performance and high Curie temperature. In this paper, we show how the addition of highly aligned porosity (between 40 and 60 vol %) improves the piezoelectric performance, sensing, and energy harvesting figures of merit in freeze-cast 0.70BiFeO3-0.30BaTiO3 piezoceramics compared to conventionally processed, nominally dense samples of the same composition. The dense and porous BF-BT ceramics had similar longitudinal piezoelectric coefficients (d33) immediately after poling, yet the dense samples were observed to age faster than those of porous ceramics. After 24 h, for example, the porous samples had significantly higher d33 values ranging from 112 to 124 pC/N, compared to 85 pC/N for the dense samples. Porous samples exhibited 3 and 5 times higher longitudinal piezoelectric voltage coefficient g33 and energy harvesting figure of merit d33g33 than dense samples due to the unexpected increase in d33 and decrease in relative permittivity with porosity. Spontaneous polarization (Ps) and remnant polarization (Pr) decrease as the porosity content increased from 37 to 59 vol %, as expected due to the lower volume of active material; however, normalized polarization values with respect to porosity level showed a slight increase in the porous materials relative to the dense BF-BT. Furthermore, the porous ceramics showed improved temperature-dependent strain-field response compared to the dense. As a result, these porous materials show excellent potential for use in high temperature sensing and harvesting applications.

The Study of Core–Shell Cobalt Ferrite–Barium Titanate Magnetoelectric Nanoparticles in Targeting and Optimized Drug Delivery: An Overview

This review provides a comprehensive understanding of magnetoelectric (ME) nanocomposite, cobalt ferrite–barium titanate (CFO–BTO) as a potential candidate for targeting specific cells. The synthesized core–shell material uses strain-mediated coupling between magnetostrictive and piezoelectric material. CFO–BTO has the competitive advantage of a high ME coefficient and is biocompatible. The shape and size play a pivotal role in passive drug delivery due to the enhanced permeability and retention effect at tumor sites. Surfactants can also enhance drug absorption and influence the interaction with nanoparticle composite. A comparison between external magnetic field–frequency parameters to navigate the ME nanoparticle and trigger release of the drug at site is also reviewed. Coating the nanoparticles with a layer of surfactant can reduce the threshold external magnetic field for navigation and triggering of drug particle release, making the prospect viable for clinical studies.

The Cavity Perturbation Technique to Detect Cobalt Ferrite and Cobalt Ferrite-Barium Titanate Core-Shell Nanocomposites in the Microwave Frequency Range for Biomedical Applications

This paper focuses on the cavity perturbation technique to measure the dielectric properties of nanoparticles: (i) cobalt ferrite (ii) barium titanate and (iii) core-shell cobalt ferrite-barium titanate. The shift in TE103 and TE105 resonant mode is compared for the above three nanomaterials which in turn is correlated to its dielectric properties. Barium titanate has the highest shift in resonance peak and it is directly proportional to its relative permittivity followed by cobalt ferrite-barium titanate and cobalt ferrite respectively. However, the half power bandwidth, Δ f is highest for the cobalt ferrite nanoparticles and least for barium titanate. Approximately 1.145 MHz shift and 3.391 MHz shift is observed for the insertion of the lossy core-shell cobalt ferrite in TE103 and TE105 modes. The quality factor for barium titante was measured to be approximately twice to that of cobalt ferrite for this particular experiment.

Phase diagrams of bismuth ferrite barium titanate thin films with misfit strains and their improved electrical properties

Phase diagrams of BiFeO3-BaTiO3 (BF–BT) thin films were constructed via thermodynamic model calculation, as well as their electrical properties. The calculated morphotropic phase boundary (MPB) of BF–BT thin films without strain is located near the composition of 0.663BF–0.337BT, which agrees well with the experimental results of reported BF–BT ceramics (between 0.66BF–0.34BT and 0.71BF–0.29BT). The permittivity, tunability and [Formula: see text]of BF–BT thin films on Si substrates are higher than those on SrTiO3(ST) plates, which are also in accordance with the measured data in the literature. Further calculation indicates that 0.7BF–0.3BT and 0.6BF–0.4BT thin films can achieve enormous piezoelectric coefficient [Formula: see text] ([Formula: see text]1200 and [Formula: see text]1000 pm/V, respectively) by selecting the substrates with the TEC respectively of 0.3 and 3.1 × 10[Formula: see text]/[Formula: see text]C, because of the phase transition from aa phase to rhombohedral phase. Such results help to clarify the phase diagrams of BF–BT thin films, implying that huge [Formula: see text]can be achieved by choosing the composition near MPB on the substrates with small TEC.

BiFeO3-BaTiO3 ferroelectrics: Decrypting the mechanism of rare earth doping-induced electrical property discrepancy via scaling behavior and multi-level structure

Rare earth doping has been widely used to modify electrical properties of piezo/ferroelectric materials. However, the physical mechanism behind property enhancement and the reason of property discrepancy induced by rare earth has been rarely solved in bismuth ferrite-barium titanate (BF-BT) ceramics. Here, two kinds of rare earth ions with different ion radii (La3+ and Sm3+) were separately introduced into Bi1-xRexFeO3-BaTiO3 (Re = La, Sm). As a result, doping an appropriate amount of rare earth ions (La3+x=0.05 and Sm3+x=0.04) can effectively improve the ferroelectricity and strain response. By combining ferroelectric scaling behavior and multi-level structure elucidation, the enhancement of electrical properties after La3+/Sm3+ doping can be attributed to the increase of total number of activated domains, the increased Bi ions off-centering and displacement of B-site ions coupled with the enhanced lattice deformation. Importantly, stronger lattice shrinkage and BO6 octahedral distortion can be achieved in Sm-doped ceramics, leading to a stronger intrinsic ferroelectric and strain response than that of La-doped ceramics, although a large enough electric field was required to release the intrinsic response because of the larger random field and dielectric relaxation induced by the larger ionic radius difference between Bi3+ and Sm3+. Oppositely, the decreased coercive field and promoted domain switching make the electrical response of La-doped ceramics can be released under a much lower electric field. The work highlights the role of rare earth doping and provides a paradigm for further designing high-performance BF-BT ferroelectrics.

Low temperature sintering, structure and electrical properties of BiFeO3-BaTiO3 based piezoelectric ceramics using CuO-B2O3 composite sintering aids

Piezoelectric ceramics usually have high sintering temperature, which cannot meet the low-temperature co-firing requirements of ceramics and metal electrodes in production of micro devices. Here, we studied the effects of CuO-B2O3 binary composite sintering aids on the sintering behavior, phase composition, microstructure, and electrical properties of the bismuth ferrite-barium titanate (0.7BiFeO3-0.3BaTiO3, BFO-BT) based lead-free piezoelectric ceramics. We found that the CuO-B2O3 sintering aids can effectively lower the sintering temperature of the BFO-BT ceramics to 880 ℃, which is far below the melting point of metal electrodes. The BFO-BT based ceramics with 0.5 wt% sintering aids exhibited excellent dielectric, ferroelectric, and piezoelectric properties (εm = 83029, Pm = 38.4 μC/cm2, Pr = 33.8 μC/cm2, d33 = 119 pC/N) with high Curie temperature (TC = 460 ℃). Meanwhile, this ceramic possessed high depolarization temperature (Td) near 300 ℃, demonstrating a good temperature stability of piezoelectricity. This study provides a feasible solution to improve the compatibility of lead-free piezoelectric materials and low-melting point metal electrodes for fabrication of micro piezoelectric devices.

Multiple Local Domain Structural Evolutions at Morphotropic Phase Boundary in BiFeO3–Ba0.9Ca0.1TiO3 Ferroelectric Ceramics

Bismuth ferrite–barium titanate (BFO–BT) is a well‐known lead‐free ferroelectric material with a large electric field‐induced strain; however, its piezoelectricity is very low under low electric fields. Herein, by studying Ca‐doped BFO–BT ceramics, multiple structural evolutions are found in the ferroelectric domains at the morphotropic phase boundary (MPB) in BFO–BT‐based ceramics, where a part of the local ferroelectric domains reveals a transition from rhombohedral to tetragonal and to relaxor phases. The superior electrical properties with large electrostrain Sp of 0.38%, large Pr of 38.4 μC cm−2, intermediate d33 of 132 pCN−1, and high TC of 425 °C are obtained at the MPB in these ceramics. Multiple local domain structural evolutions with compound ferroelectric domains and relaxor phases are responsible for the large electrostrain and intermediate piezoelectricity. This can explain the inconsistent piezoelectric response under high and low electric fields at the MPB in the BFO–BT‐based ferroelectric ceramics.

Bismuth ferrite-barium titanate system studies around morphotropic phase boundary

Nowadays, the electro-electronic industry and scientific community have a great interest in improving memory devices. A candidate is the bismuth ferrite owing to the coexistence of ferroelectricity and anti-ferromagnetism at room temperature, however, a high leakage current harms their ferroelectric properties. Thus, bismuth ferrite and barium titanate solutions improve the ferroelectric properties of bismuth ferrite and optimize the magnetoelectric coupling factor. This system is called multiferroic, materials exhibit the coexistence of ferromagnetic, ferroelectric, or ferro-elastic orders, which is of interest to the scientific physics community and electronic industry. In this paper, bismuth ferrite-barium titanate system around the morphotropic phase boundary was studied and analyzed. It was observed changes in the structural properties in function of barium titanate content. Calcination temperature was determined from thermogravimetric analysis curves to powders of bismuth ferrite-barium titanate system. Ceramic bodies were densified conventionally. Archimedes’ method was used for density measure. Ceramics with densities greater than 95% were obtained. 93% of the perovskite phase was obtained from structural results. Finally, structural properties were presented and analyzed using Mossbauer spectroscopy as complementary technique. These analyses are very important in solid state physics because to contribute to understanding the phenomenology and synthesis process of multiferroic materials.

Hyperthermia Using Magnetic Cobalt Ferrite Magnetoelectric Nanoparticles

The focus of this article is to understand the application and the factors influencing magnetic hyperthermia using cobalt ferrite nanoparticles. Intrinsic properties, such as particle size, specific absorption rate, and magnetic saturation, are correlated with the material’s property to generate hyperthermia. External factors, such as the magnitude of applied field frequency, also influence the rate of hyperthermia generated by magnetic nanoparticles. Quantitative analysis of Pennes bioheat equation and finite element analysis (FEA) using COMSOL are used to understand the transient increase in temperature at the tumor site using magnetic nanoparticles. The required temperature for generating hyperthermia using nanoparticles is approximately 315 K or 42 °C. Due to the intrinsic high rate of metabolism in tumor cells, the required magnetic field to induce transient increase at the malignant cell site is less than its surrounding healthier cells. This principle can therefore be applied for inducing selective hyperthermia in tumor cells by the application of a lower threshold external magnetic field. This article focuses on the Pennes bioheat equation to understand the phenomenon of heat transfer as a function of both the time and the applied field magnitude. It compares the difference in the rate of heat transfer for 1) cobalt ferrite and cobalt ferrite–barium titanate and 2) hyperthermia in healthier and tumor sites using magnetic nanoparticles. An FEA is performed in conjunction to understand the rate of temperature profile change occurring at a simulated cell site.

Synthesis and characterization of bismuth ferrite-barium titanate nano composites

Bismuth ferrite and Strontium doped bismuth ferrite(Bi1-xSrxFeO3(x=0.0,0.3,0.5,0.7) samples are synthesized by the modified sol-gel technique which is a simple and economic technique.Composites of bismuth ferrite and barium titanate in the ratio 2:1 and 1:2 and Bi1-xSrxFeO3 – BaTiO3 (x=0.3,0.5,0.7) with the ratio 2:1 are synthesized by solid-state reaction technique. The formation of composites of bismuth ferrite with rhombohedral structure and space group R3c and barium titanate with tetragonal structure and space group P4mm is identified using XRD. The dielectric and ferroelectric properties of the composites are investigated at room temperature and are reported in this paper.

Modeling of core-shell magneto-electric nanoparticles for biomedical applications: Effect of composition, dimension, and magnetic field features on magnetoelectric response.

The recent development of core-shell nanoparticles which combine strain coupled magnetostrictive and piezoelectric phases, has attracted a lot of attention due to their ability to yield strong magnetoelectric effect even at room temperature, thus making them a promising tool to enable biomedical applications. To fully exploit their potentialities and to adapt their use to in vivo applications, this study analyzes, through a numerical approach, their magnetoelectric behavior, shortly quantified by the magnetoelectric coupling coefficient (αME), thus providing an important milestone for the characterization of the magnetoelectric effect at the nanoscale. In view of recent evidence showing that αME is strongly affected by both the applied magnetic field DC bias and AC frequency, this study implements a nonlinear model, based on magnetic hysteresis, to describe the responses of two different core-shell nanoparticles to various magnetic field excitation stimuli. The proposed model is also used to evaluate to which extent realistic variables such as core diameter and shell thickness affect the electric output. Results prove that αME of 80 nm cobalt ferrite-barium titanate (CFO-BTO) nanoparticles with a 60:40 ratio is equal to about 0.28 V/cm∙Oe corresponding to electric fields up to about 1000 V/cm when a strong DC bias is applied. However, the same electric output can be obtained even in absence of DC field with very low AC fields, by exploiting the hysteretic characteristics of the same composites. The analysis of core and shell dimension is as such to indicate that, to maximize αME, larger core diameter and thinner shell nanoparticles should be preferred. These results, taken together, suggest that it is possible to tune magnetoelectric nanoparticles electric responses by controlling their composition and their size, thus opening the opportunity to adapt their structure on the specific application to pursue.

Origin of large piezoelectricity in BF-BT based multiphase ferroelectrics

Bismuth ferrite-barium titanate (BF-BT) based ferroelectrics with multi-phase coexistence exhibit promising piezoelectricity, while whose physical mechanism of property enhancement is poorly understood. In the present work, the Rayleigh law, in-situ electric field dependent synchrotron X-ray diffraction and ex-situ piezo-response force microscopy were utilized to gain insight into the property and structure evolution characteristics under electric fields. Extrinsic contribution from domain wall motion was regarded as the major determiner in piezoelectricity of the 0.69Bi1.05Fe0.99Sc0.01O3-0.3BaTiO3-0.01Bi1.05(Zn0.5Hf0.5)O3 ferroelectrics with rhombohedral and pseudo-cubic phase coexistence, different from those proposed structural origins in BF-BT based relaxor ferroelectrics (with high BT content) with large strain response. By analyzing the property discrepancy between unpoled and poled samples, the enhanced polarization and electro-strain in poled ceramics were attributed to the activated domain state induced by the direct current pre-poling.

Constructing Relaxor/Ferroelectric Pseudocomposite To Reveal the Domain Role in Electrostrain of Bismuth Ferrite-Barium Titanate Based Ceramics.

Bismuth ferrite-barium titanate (BF-BT) based ceramics have attracted extensive attention due to its excellent energy conversion. Recently it has been found that BF-BT based ceramics with large electrostrain are usually accompanied by a special domain configuration in which weak and strong piezoresponse domain grains coexist. In this work, we purposefully constructed the special domain configuration in the pseudocomposite ceramics of (1 - x)0.55BF-0.4BT-0.05BZN/x(0.7BF-0.3BT) (relaxor-like phase/ferroelectric phase, RE/FE) by a "two-step" method. Macroproperty characterization suggests that the critical component pseudocomposite ceramic (x = 50%) with the special domain structure can exhibit a maximum electrostrain value (S ∼ 0.28%) at 6 kV/mm, almost 3-fold to that (S ∼ 0.1%) of the two end members and 63% higher than that (S ∼ 0.17%) of the same component ceramic prepared by the "one-step" method. Further mesoscopic structure results show that the "two-phase" composite can induce the formation of grain dependent domain at nanoscale, and just this special domain conformation is conducive to a significant improvement in electrostrain. Therefore, the large strain in BF-BT-based ceramics is mainly caused by the special microstructure rather than component.

Magnetic and Optical Characterization of Cobalt Ferrite–Barium Titanate Core–Shell for Biomedical Applications

Magnetic and Optical Characterization of Cobalt Ferrite–Barium Titanate Core–Shell for Biomedical Applications

Magnetoelectric core-shell CoFe2O4@BaTiO3 nanorods: their role in drug delivery and effect on multidrug resistance pump activity in vitro.

Nanoparticle mediated targeted drug delivery has become a widespread area of cancer research to address premature drug delivery problems. We report the synthesis of magneto-electric (ME) core–shell cobalt ferrite-barium titanate nanorods (CFO@BTO NRs) to achieve “on demand” drug release in vitro. Physical characterizations confirmed the formation of pure CFO@BTO NRs with appropriate magnetic and ferroelectric response, favorable for an externally controlled drug delivery system. Functionalization of NRs with doxorubicin (DOX) and methotrexate (MTX) achieved up to 98% drug release in 20 minutes, under a 4 mT magnetic field (MF). We observed strong MF and dose dependent cytotoxic response in HepG2 and HT144 cells and 3D spheroid models (p < 0.05). Cytotoxicity was characterized by enhanced oxidative stress, causing p53 mediated cell cycle arrest, DNA damage and cellular apoptosis via downregulation of Bcl-2 expression. In addition, MF and dose dependent inhibition of Multidrug Resistance (MDR) pump activity was also observed (p < 0.05) indicating effectivity in chemo-resistant cancers. Hence, CFO@BTO NRs represent an efficient carrier system for controlled drug delivery in cancer nanotherapeutics, where higher drug uptake is a prerequisite for effective treatment.

Decoding Thermal Depolarization Temperature in Bismuth Ferrite-Barium Titanate Relaxor Ferroelectrics with Large Strain Response.

Bismuth ferrite-barium titanate (BF-BT) ferroelectrics attract attention due to their multifunctional properties and potential applications in high-temperature piezodevices. The thermal depolarization temperature (Td) of BF-BT-based relaxor ferroelectrics has a close correlation with electrical properties, which was only recently discovered and is not well recognized. This work is concerned with the thermal depolarization process in (0.67 - x)BF-0.33BT-xSZ ferroelectrics with large strain response. Macro-to-local property characterization suggests that the largest electrostrain can be achieved in the critical component (x = 0.02) with the most flexible structure features, which is the transition point from the ferroelectric macrodomain to the relaxor nanodomain. The real-space domain image by piezoresponse force microscopy has revealed that an electric field can transform the labyrinth-like nanodomain into oriented large-size domain. Once the heating temperature is above Td, the poling-induced large-size oriented domain will transform back to its initial state. Most importantly, the thermally induced domain broken is first established with the conduction and phase transition, as disclosed by temperature dependence of DC resistivity and the pyroelectric coefficient. That is, during the thermal depolarization process, the activation energy (Ea) changes from 0.65 eV (T < Td) to 1.1 eV (T > Td), simultaneously accompanied with the structural transition from the poling-induced unstable ferroelectric state (long-range correlated rhombohedral phase) to the initial relaxor state (short-range correlated pseudo-cubic phase), which may be the driving force for the domain decays above Td. We believe that the understanding of Td in BF-BT-based relaxor ferroelectrics can provide some clues for further designing high-performance BF-BT ferroelectrics.

Competitive mechanism of temperature-dependent electrical properties in BiFeO3-BaTiO3 ferroelectrics controlled by domain evolution

To understand the structure nature and physical mechanisms of property evolution under electric and temperature fields, temperature-dependent electrical properties of bismuth ferrite-barium titanate (BiFeO3-BaTiO3, BF-BT) ceramics were analyzed from both static structure and domain dynamics. Intriguingly, temperature coefficient of remanent polarization (Pr) and negative strain (Sneg) changes from positive to negative as BT component increases, leading to a nearly zero temperature coefficient of Pr at critical component (BT=0.35). Combined with multi-scale structure characterization techniques and polarization switching/backswitching described by the temperature-dependent Ps and Ps-Pr, such behavior is explained by the evolution of domain size for the first time and a competitive mechanism is also proposed. That is, the evolution of macro stripe domain (0.25≤BT≤0.30) to nanodomain (0.35≤BT≤0.45) determines the transition from the dominated polarization switching process to the dominated backswitching process, further greatly determining the temperature-stability of strain properties: variation of unipolar strain changes from 136% (BT=0.25) to 25% (BT=0.45) with increasing BT content. We believe that these results significantly guide the performance improvement (especially temperature-dependent properties) of BF-BT solid solutions.