FeO3 Ceramics Research Articles

Simultaneously enhanced ferroelectric and magnetic properties of SrTiO3‐modified Bi0.88Sm0.12FeO3 ceramics

AbstractIn the present study, SrTiO3 was selected to enhance the multiferroic characteristics of Bi0.88Sm0.12FeO3 (BSF) ceramics. With increasing SrTiO3 content, the principal phase of BSF ceramic transitions from rhombohedral R3c to Pna21. Through DSC and dielectric analysis, it was observed that both the Curie temperature and Néel temperature decreased proportionally with the augmentation of SrTiO3 content. When x = .1, the optimal ferroelectric performance is achieved, and the highest remanent polarization value is 55.47 µC/cm2, significantly surpassing that of BSF ceramics. Moreover, the PFM test results showed that as the substitution content increased, the domains in the BSF ceramic gradually transformed from normal ferroelectric domains to polar nanomicro‐domains. Magnetic and magnetoelectric results show that when x = .1, the best magnetic properties are obtained, Mr = 59.7 emu/mol. The magnetoelectric coefficient αME initially increased and then decreased with the increasing SrTiO3 content, reaching its optimum magnetoelectric properties at x = .1, where αME = .47 mV cm–1 Oe–1. In summary, when the substitution amount of SrTiO3 reaches 10%, the ferroelectric, magnetic, and magnetoelectric properties of BSF ceramics are significantly improved.

Influence of synthesis method on structural, microstructural, and magnetic properties of Bi0.5La0.5FeO3 ceramics

Influence of synthesis method on structural, microstructural, and magnetic properties of Bi0.5La0.5FeO3 ceramics

Realizing Outstanding Energy Storage Performance in KBT-Based Lead-Free Ceramics via Suppressing Space Charge Accumulation.

The great potential of K1/2Bi1/2TiO3 (KBT) for dielectric energy storage ceramics is impeded by its low dielectric breakdown strength, thereby limiting its utilization of high polarization. This study develops a novel composition, 0.83KBT-0.095Na1/2Bi1/2ZrO3-0.075 Bi0.85Nd0.15FeO3 (KNBNTF) ceramics, demonstrating outstanding energy storage performance under high electric fields up to 425kVcm-1: a remarkable recoverable energy density of 7.03Jcm-3, and a high efficiency of 86.0%. The analysis reveals that the superior dielectric breakdown resistance arises from effective mitigation of space charge accumulation at the interface, influenced by differential dielectric and conductance behaviors between grains and grain boundaries. Electric impedance spectra confirm the significant suppression of space charge accumulation in KNBNTF, attributable to the co-introduction of Na1/2Bi1/2ZrO3 and Bi0.85Nd0.15FeO3. Phase-field simulations reveal the emergence of a trans-granular breakdown mode in KNBNTF resulting from the mitigated interfacial polarization, impeding breakdown propagation and increasing dielectric breakdown resistance. Furthermore, KNBNTF exhibits a complex local polarization and enhances the relaxor features, facilitating high field-induced polarization and establishing favorable conditions for exceptional energy storage performance. Therefore, the proposed strategy is a promising design pathway for tailoring dielectric ceramics in energy storage applications.

Effect of Mn substitution-driven structural transition on magnetic and optical properties of multiferroic Bi0.85La0.15FeO3 ceramics

Effect of Mn substitution-driven structural transition on magnetic and optical properties of multiferroic Bi0.85La0.15FeO3 ceramics

Octahedra tilt influencing physical properties of polycrystalline Bi0.9Co0.1FeO3 ceramics

ABSTRACT Recently, multiferroic materials such as BiFeO3 have fascinated researchers for their potential application in memory storage devices. However, high leakage, weak magnetism and magnetoelectric coupling in this system restrict its practical applications. To solve this, the octahedra tilt influencing electrical, magnetic and thermal properties of polycrystalline Bi0.9Co0.1FeO3 ceramics via solid state route is studied here. Cobalt doped BiFeO3 affect the structural arrangement and tunes the crystal engineering of BiFeO3. In particular, the temperature-dependent dielectric behaviour of Bi0.9Co0.1FeO3 shows a significant dielectric anomaly corresponding to the magnetoelectric coupling in this sample. Further, the maximum magnetization of Bi0.9Co0.1FeO3 is 8.70 emu/ g which is two orders higher in magnitude compared to pristine BiFeO3.

Effects of oxygen vacancies on electric properties of high valence ions Mo/Zr/Ti doped Bi0.85Nd0.15FeO3 ceramics with morphotropic phase boundary

The effects of oxygen vacancies on electric properties of high valence ions (Mo/Zr/Ti) doped Bi0.85Nd0.15FeO3 (marked as BNFM, BNFZ, BNFT) ceramics with morphotropic phase boundary (MPB) are investigated. MPB structures consisting of rhombohedral, intermediate and orthorhombic phases exist in all samples, which is confirmed by the XRD Rietveld refinements and TEM analyses. The BNFT has the maximum remnant polarization of 34.5 μC/cm2 at 180 kV/cm, owing to its lowest paraelectric orthorhombic phase content. XPS and impedance results reveal that the BNFT ceramic has the relatively low oxygen vacancy contents and the largest impedance value, which is beneficial for the ferroelectric test. The best comprehensive properties of BNFT open wide prospects for improving BiFeO3-based ceramics.

Optimizing Structural, Optical, Dielectric, and Magnetic Properties of (Bi1-x La x )FeO3 (0.00 ≤ x ≤ 0.06) Sintered Ceramics.

(Bi1-x La x )FeO3 (0.00 ≤ x ≤ 0.06) ceramics have been synthesized through a mixed oxide route to investigate their structural, morphological, optical, dielectric, and magnetic properties. All the samples are revealed to be in rhombohedral structures along with the R3c space group and 161 space group number. A high relative permittivity and the lowest tangent loss are observed in BLFO samples at the frequency range 1-100 MHz. The optical studies show that the excitation energy increases with the increasing La content. Moreover, the magnetization being strongly affected by crystallite size and microstrain has been investigated. The band gap energy increases with the increasing La content. The overall result of pure and doped La contents in BFO ceramics shows enhanced structural, dielectric, and optical properties.

Multiferroic Properties of Lead-Free (1 − x)(K0.44Na0.52Li0.04)(Nb0.84Ta0.10Sb0.06)O3 − xBi0.8Ba0.2FeO3 Ceramics Prepared via the Solid-State Combustion Technique

Multiferroic Properties of Lead-Free (1 − x)(K0.44Na0.52Li0.04)(Nb0.84Ta0.10Sb0.06)O3 − xBi0.8Ba0.2FeO3 Ceramics Prepared via the Solid-State Combustion Technique

Strain induced structural phase transition and compositional dependent magnetic phase transition in Ti doped Bi0.80Ba0.20FeO3 ceramics

Bi0.80Ba0.20Fe1-xTixO3 (0≤x≤0.10) samples are prepared using solid state reaction technique. Bi3+ site is replaced with 20 % Ba2+ which induced structural modification from rhombohedral to pseudo cubic accompanied by the creation of oxygen vacancies owing to the charge reimbursement. Fe3+ site is replaced with different concentrations of Ti4+ keeping Ba content fixed. All the samples exhibited similar morphology and no significant variation in grain size is observed by substituting Ti at Fe site. All of the samples exhibited ferromagnetic behavior, which is ascribed to the destruction of spiral spin structures and changes in super-exchange interaction strength caused by variations in bond lengths of Fe–O and Fe–O–Fe. The decrease in magnetization with increasing Ti concentration is due to magnetic moment dilution caused by non-magnetic Ti4+. An anomalous trend in magnetization is observed for magnetic measurements at low temperature (77 K) where structural transformation from ferromagnetic to diamagnetic behavior was noted for 10% Ti content. Further, because of the incorporation of Ti4+, an improved dielectric property was observed due to increase in resistivity and decrease in the defect concentration (oxygen vacancies). In the present study, it was concluded that optimum concentration of Ba2+ (20%) and Ti4+ co-doped BiFeO3 systems have shown enhanced multiferroic properties at room temperature.

Influence of rare-earth doping on the structural and magnetic properties of orthoferrite La0.50R0.50FeO3 ceramics obtained under high pressure

Studies on the impact of co-doping on the structural, magnetic, and magnetocaloric properties of LaFeO3 orthoferrite-based compounds with partial isovalent substitution of La3+ by rare-earth (R) ions have been carried out. Their functional properties have been experimentally and theoretically investigated by X-ray diffraction analysis, differential scanning calorimetry, and magnetic methods as well as a semiempirical approach. The La0.50R0.50FeO3 (R = Nd, Eu, Gd, Dy, Er) ceramics have been taken as a basis and prepared by a solid-state reaction method under cold-pressing at high pressure (P = 4 GPa). The temperature dependences of the magnetization and magnetocaloric characteristics of the La0.50R0.50FeO3 orthoferrites for the whole series of substitutions from R = Ce to Lu have been calculated within the framework of the semiempirical model, assuming linearity of its parameters depending on the R cation radius. The magnetic entropy change ΔSM, relative cooling power RCP, and specific heat capacity ΔCP,H have thereby been obtained. It has been shown that the La0.50Ce0.50FeO3 composition has the highest magnetocaloric parameters with the lowest Néel temperature TN. As the R cation radius decreases, the chemical pressure increases, leading to a decrease in the magnetocaloric characteristics and an increase in TN. This is due to both a size effect of the crystallites and structural distortions. The obtained results show the potential practical applications of orthoferrite-based materials with controlled magnetocaloric effect and phase transition temperature.

Giant electric field–controlled magnetism in Bi0.86Sm0.14FeO3 multiferroic ceramics with Pna21 symmetry

AbstractIn the present work, Bi0.86Sm0.14FeO3 ceramics with near Pna21 single‐phase structure were obtained by a repeated longtime sintering process, and the dielectric, ferroelectric, and magnetic characteristics were determined together with the magnetoelectric coupling coefficient. The evolution of Pna21 symmetry was revealed by transmission electron microscope analysis, and the ferroelectric transition from Pbnm to Pna21 was determined by differential scanning calorimetry analysis together with the dielectric characterization, and the Curie temperature was determined as 195°C. The saturated polarization–electric field (P–E) hysteresis loop was obtained with Pr = 12.2 μC cm−2, and the unlocking of ferromagnetism was confirmed by the apparent magnetization–magnetic field (M–H) hysteresis loop with Mr = 77.4 emu mol−1. The giant electric field–controlled magnetism was due to the Pna21/R3c field–induced transition, which was confirmed by both structure analysis and theoretical calculation, and the change of remanent magnetization under an electric field was achieved up to 44.8 emu mol−1 (57.9%), which was much bigger than that of rare‐earth (RE)‐substituted BiFeO3 ceramics without optimizing Pna21 phase fraction. The present results might significantly deepen the physical understanding of Pna21 phase and subsequently provide new hints on further enhancing electric field–controlled magnetism in RE‐substituted BiFeO3 multiferroic ceramics.

Energy storage performance of polycrystalline Bi0.85Ho0.05Sm0.1FeO3 ceramics

This article analyzes the energy storage performance of polycrystalline Bi0.85Ho0.05Sm0.1FeO3 ceramics. The sample is synthesized by a solid-state reaction and, it crystallizes in the R3c phase without any traces of secondary phases. The electron density distribution and type of bonding are analyzed using the maximum entropy method. The energy storage capability of polycrystalline Bi0.85Ho0.05Sm0.1FeO3 ceramics was determined to be 0.212 J/cm3 and 0.332 J/cm3 at 2 Hz and 100 Hz frequencies, respectively.

Enhanced UV photosensing properties by field-induced polarization in ZnO-modified (Bi0.93Gd0.07)FeO3 ceramics

Self-powered photodetection was studied using x wt% ZnO-modified (Bi0.93Gd0.07)FeO3 (abbreviated as B7GFO-xZn) ferroelectric ceramics. The ITO/B7GFO-xZn ceramic/Au photovoltaic (PV) cell was constructed for photosensing study at ultraviolet-A (λ = 360 nm) and near-ultraviolet (λ = 405 nm). The +2kV/cm poled PV cell using B7GFO-1 wt%Zn ceramic under 360-nm irradiation displays maximal photocurrent density of ~364 μA/cm2 at 102 mW/cm2. Furthermore, a remarkable photosensing performance was observed with photoresponsivity (R) of ~3.02×10−2A/W, specific detectivity (D*) of ~2.27×1012 Jones, and photoconductive gain (G) of ~10.4%. A sensitive photosensing response time (rise time, τr) of ~9 ms was acquired under illumination from the 360-nm laser at 102 mW/cm2. The enhanced photodetection performance originated from the collective influence of the narrower bandgap, enhanced p-n junction effect, E-field-modulated energy band tilt, and improved photocurrent generation due to the local conductive pathways formed by the interconnected domain walls and grain boundaries. This work provides an extensive analysis to elucidate the photovoltaic mechanisms in BiFeO3-based ceramics and explores their potential in self-powered UV photosensing.

Strain Induced Structural Phase Transition and Compositional Dependent Magnetic Phase Transition in Ti Doped Bi0.80Ba0.20FeO3 Ceramics

Strain Induced Structural Phase Transition and Compositional Dependent Magnetic Phase Transition in Ti Doped Bi0.80Ba0.20FeO3 Ceramics

Influence of Rare-Earth Doping on the Structural and Magnetic Properties of Orthoferrite La0.50r0.50feo3 Ceramics Synthesized Under High Pressure

Influence of Rare-Earth Doping on the Structural and Magnetic Properties of Orthoferrite La0.50r0.50feo3 Ceramics Synthesized Under High Pressure

Negative zero‐field‐cooled magnetization and magnetic switching in multiferroic Lu0.5Sc0.5FeO3 ceramics

AbstractIn this study, we have investigated the negative magnetization of Lu0.5Sc0.5FeO3 (LSFO) ceramics in the zero‐field‐cooled (ZFC) mode. The negative magnetization in ZFC measurement appears below the Neél temperature (TN) in LSFO, which is probably caused by the residual negative trapping field in superconducting magnet, and is closely related to the giant coercivity in LSFO. By fitting the high‐temperature paramagnetic data under nominal zero magnetic field, the negative trapping field in superconducting magnet is found to be −3.28 Oe. The giant coercivity is ascribed to the strong uniaxial magnetocrystalline anisotropy in LSFO, which can cause the strong magnetic domain wall pinning effect to limit the nucleation of reversed domains under reverse field. In addition, a switchable magnetization switching is realized in LSFO. The magnetization of LSFO can stably switch between positive and negative values when the applied magnetic field was switched between 0.5 and 3 kOe, which suggests that the LSFO samples are suitable for potential applications in magnetic storage.

The involvement of Pna21 phase in the multiferroic characteristics of La/Lu co-substituted BiFeO3 ceramics

Rare earth ion (RE)-substitution has been recognized as an effective way for improving multiferroic properties especially for realizing the electric field-controlled magnetism in BiFeO3 ceramics, where the symmetry modulation of R3c-Pna21-Pbnm and unlocking ferromagnetism by destroying the cycloidal spin structure are the key points. In Lu-substituted BiFeO3 ceramics, however, the Pna21 phase is not involved. In the present work, La/Lu co-substitution was investigated to involve the Pna21 phase in BiFeO3 ceramics. The phase transition from R3c to Pna21 occurred with an increase in x, and the mixed structure of R3c, Pna21, and Pbnm phases was determined in Bi0.82−xLaxLu0.18FeO3 ceramics. The greatly enhanced ferroelectric polarization and the switching from antiferromagnetic to the weak ferromagnetic state through the destruction of the cycloidal spin structure were achieved. Subsequently, the direct magnetoelectric coupling coefficient αME up to 2.02 mV/cm Oe was obtained. The increased effective ionic radius of RE in the present ceramics played a key role in involving Pna21 phase in RE-substituted BiFeO3 ceramics, and the critical value was about 0.104 23(2) nm.

Influence of Compacting Pressure on the Dielectric Properties of La-modified Bismuth Ferrite Multiferroics Prepared by Rapid Liquid-phase Sintering Method

Structure, perovskite phase formation, chemical and phase composition, microstructure, morphology and dielectric properties of the single-phase lanthanum-modified bismuth ferrite multiferroic ceramics obtained by the rapid liquid-phase sintering method under different compacting pressures have been investigated using X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, thermogravimetry/differential thermal analysis and dielectric spectroscopy methods. The temperature and time for an express preparation of the single-phase Bi0.9La0.1FeO3 ceramics with formation of a perovskite structure have been found out. With an increase in the compacting pressure P from 100 to 1100 MPa, the dielectric constant ε′ changes by ∼25% and ∼80% in the low-frequency and ultra-high frequency ranges, respectively. In the low-frequency range, all samples depending on the pressure P demonstrate excellent dielectric behavior with a stable dielectric constant and quite low dielectric loss that make these samples perspective for their possible practical application in microelectronic and spintronic.

La doped BiFeO3 ceramics synthesized under extreme conditions: Enhanced magnetic and dielectric properties

Multiferroic Bi0.85La0.15FeO3 powders and ceramics were synthesized under extreme conditions by a combination of high-energy ball cryomilling, fast firing and spark plasma sintering procedures. Single-phased and perovskite structured samples, where both rhombohedral (R3c space group) and orthorhombic (Pnma) phases coexist, were successfully processed. Highly dense (7.92 g/cm3, 97.5% of the theoretical one) and electrically resistive (2.19×1011Ω⋅cm) nano-structured ceramics with high internal micro-strain levels (up to 1.08%), small crystallite size (24 nm) and elevated magnetization (ranging from 0.204 to 0.350 emu/g at 15 kOe) with an expressive non-linear response were obtained by combining cryomilling, SPS and oxidative annealing. Particularly, the dielectric response is improved by oxidative annealing at 200 °C, reaching 170 at 1 kHz with very low loss tangent (2.5%). This study demonstrated the effectiveness of the chosen synthesis route in the production of BFO-based ceramics with enhanced ferroic properties.

Electric field poling effect on the photosensitivity of samarium-doped bismuth ferrite ceramics

This work highlights improved photosensing performance in ITO/(Bi0.93Sm0.07)FeO3/Au heterostructure through a prior electric field poling. Maximal responsivity (R) of 2.0×10−2A/W and specific detectivity (D*) of 2.2×1011 Jones were obtained under 405-nm irradiation. The mechanism behind the observed photosensing performance is linked to the combined effects of the polarization-induced electric field and built-in electric fields at the interfaces (i.e., p–n junction and Schottky barrier). The net internal electric field established in the device serves as the driving force for the separation and transport of the photo-generated electron–hole pairs. The reduced direct optical bandgap (Eg) of 2.13 eV, the well-defined ferroelectric polarization hysteresis loops, and the conduction pathways formed by the electric field-stimulated interconnection of domain walls and grain boundaries play significant roles in the remarkable photosensitivity of (Bi0.93Sm0.07)FeO3 ceramics, thus providing insight into optimizing BiFeO3-based materials for near-UV photodetector.