Doped BFO Research Articles

Investigating the influence of Cu and Ti substitution on the structural, optical, and dielectric properties of BiFeO3.

The environmentally friendly BiFe1-x(Ti1/2Cu1/2)xO3 system with various substitution rates, including x = 0 (BFO), x = 0.02 (BFTCO2) and x = 0.04 (BFTCO4), has been synthesized using the solid-state reaction technique. All compositions exhibited a distorted rhombohedral structure with R3c space, as observed from the results of XRD and Raman spectroscopy. A significant impurity phase (Bi25FeO40) appears in pure and doped BFO, with a percentage ranging between 6 and 9%. This impurity was also detected using Mössbauer spectroscopy. UV-vis spectroscopy revealed a decrease in optical band energy with the substitution, suggesting the potential applications of doped BFO within the visible range of the spectrum, making it suitable for photocatalytic and solar cell applications. The smallest bandgap was observed for BFTCO2 with Eg = 1.93 eV. The origin of this reduction is discussed from a scientific point of view. Furthermore, Cu2+ and Ti4+ co-doped BFO display an improvement in dielectric properties due to the reduction in the value of tan δ. Dielectric measurements revealed an anomaly below TN with diffusive and dispersive behavior, suggesting a relaxor-like behavior for all compositions. The relaxor character was quantified by using the Vogel-Fulcher relationship which yielded activation energy of 0.359-0.614 eV. In our system, the relaxor behavior showed an enhancement with the heterogeneity created by the substitution rate, reaching its maximum for BFTCO4, characterized by the empirical parameters which are: ΔTrelax = 96 K and γ = 1.96. Finally, co-doped BFO ceramics not only present promising materials for optical applications due to the narrow bandgap, but their relaxor behavior can also be tailored for promising applications in high-energy storage devices.

Ferroelectric‐Photocatalysts for Degradation of Phthalate: Doped BiFeO3‐Graphene Oxide Nanocomposites

AbstractA complete photocatalytic degradation of dibutyl phthalate (DBP) using ferroelectric doped‐bismuth ferrite‐ (BiFeO3; BFO) graphene oxide (GO) nanocomposites is achieved. The local ferroelectric properties of doped BFO photocatalysts supported onto GO is well‐utilized for photodegradation of pollutant. A complete photodegradation of DBP under ultraviolet light irradiation is achieved within 2.5 h, traced by gas chromatography. The best photocatalytic activity of Bi0.95Ag0.05Fe0.95Mn0.05O3‐GO (ABMGO) nanocomposite is attributed to its large intrinsic local ferroelectric polarization, which suppresses the recombination of photoinduced charge carriers and the presence of Ag+ and Mn4+ as new active sites on the large surface of ABMGO speeds up the photodegradation of DBP. The possible mechanism of photodegradation of DBP is presented using mass spectrometry includes several intermediate products; phthalic acid, benzoic acid, benzaldehyde, and hydroquinone and 3‐methyl butyric acid which are harmless for the environment compared to DBP.

Photovoltaic energy conversion in multiferroic perovskite absorber-based devices via experiment and theoretical calculations

Initially, La and Ti-doped BiFeO3 (BLFTO) was prepared through the solid-state method, and the formation of perovskite structure was confirmed through powder X-ray diffraction (XRD) analysis. SEM-EDX analysis confirms the merging of grains for the increasing concentration of Ti ion doping and the presence of all elements in the samples. The bandgap tuning in BLFTO (2.05 eV–2.11 eV) was analyzed through UV–vis spectroscopy and confirming the change in bandgap for Ti-doped BLFO samples. The observed energy bandgap range of the doped BFO absorber suggested its potential applications in solar cell devices. Therefore, we have designed lead-free FTO/TiO2/absorber/Spiro-OMeTAD/Au heterostructure device and achieved a power conversion efficiency (PCE) of ∼5.61% with an open-circuit voltage (VOC) of ∼0.91 V, fill factor (FF) of 55.55%, and current density (JSC) of 10.87 mA/cm2 for lead-free doped Bi0.80La0.20Fe1−xTixO3 (x = 0.0) based perovskite solar cells with proper optimization of thickness of absorber and operating temperature.

STRUCTURE, PHONON VIBRATIONAND ELECTRICALPROPERTIESOFBa2+ DOPEDBISMUTH FERRITE


 
 
 Multiferroic Bi1-xBaxFeO3 (BBFO) (x = 0.0, 0.1, 0.2, 0.25, 0.3) nanoparticles were successfully synthesized utilizing sol–gel process. The structure of the prepared samples was characterized by employing x-ray diffraction technique. The results confirmed the transformation of crystal structure from rhombohedral to tetragonal at x ≥ 0.25. Infrared (IR) reflectivity spectra measured at ambient temperature in the frequency range 10-7500 cm-1. The resonant frequency, oscillator strength and the damping factor of all modes were computed by fitting the IR reflectivity spectra to the classical Lorentz oscillator model. From the temperature dependent electrical resistivity, Ba2+ doped BFO exhibited metallic behavior at low temperature, which transform to semiconducting behavior on increasing the temperature. The temperature of this metal to semiconductor (MS) transition depends on doping concentration of Barium.
 
 

Morphotropic Phase Boundary Enhanced Photocatalysis in Sm Doped BiFeO3.

This paper presents the results of the synthesis of samarium-doped bismuth ferrite (BFO) nanoparticles by the solution combustion method. The dependence of BFO properties on the amount of the samarium (Sm) in the composition was studied. The synthesized nanocomposites were characterized by scanning electron microscopy SEM), X-ray diffractometry (XRD), Raman, Electron Diffuse Reflectance Spectroscopy (EDRS) and Electron Magnetic Resonance (EMR). The photocatalytic (PC) measurements showed the absence of a strict correlation between the PC activity and the crystallite size and band gap. An increase in the PC activity of BFO samples with 10 and 15% doping was observed and it was concluded that in controlling the PC properties in doped BFO, the processes of interfacial polarization at the boundaries of the morphotropic phase transition are of decisive importance. It was supposed that the internal electric field formed at these boundaries contributes to the efficient separation of photogenerated charge carriers.

Study of the role of dysprosium substitution in tuning structural, optical, electrical, dielectric, ferroelectric, and magnetic properties of bismuth ferrite multiferroic

Magnetoelectric multiferroics, which combine ferroelectric and magnetic characteristics, have potential use in a variety of electronic devices. In this work, Dy 3+ substituted bismuth ferrites with the chemical formula Bi 1−x Dy x FeO 3 ( x = 0.0, 0.15, 0.30, 0.45, and 0.60) were synthesized using the sol-gel auto combustion process. The effect of Dysprosium substitution in BiFeO 3 (BFO), on its structural, surface morphology, optical, electrical, dielectric, ferroelectric, and magnetic properties were studied. The rhombohedral perovskite structure of the space group ( R3c ) was confirmed via X-ray diffraction (XRD) analysis. Moreover, the crystallite size had a maximum value of 59.57 nm for x = 0.30. XRD and FTIR confirmed the substitution of Dy 3+ into BFO ferrite. Further, the structural change and absorption bands confirmed the substitution of Dy 3+ ions into the lattice. For x = 0.30, the energy bandgap of 2.81 eV was found. The resistivity and activation energy were minimum and drift mobility was maximum at x = 0.30 as compared to Dy 3+ doped BFO samples. At low frequency, the dielectric loss was reduced, while at high frequency, the dielectric loss increased with increasing frequency. The saturated polarization ( P S ), electric polarization ( E C ), and remnant polarization ( P r ) have values of 6.95 µC/cm 2 , 3.49 µC/cm 2 , and 1.53 kV/cm for x = 0.30, respectively. The maximum saturation magnetization and microwave frequencies were 10.89 emu/g and 2.41 GHz, respectively at Dy 3+ concentration x = 0.30. These materials are suitable for electronic and microwave devices. • Bi 1- x Dy x FeO 3 ( x = 0.0, 0.15, 0.30, 0.45, and 0.60) multiferoaic were successfully prepared via simple sol-gel auto-combustion. • The optical bandgap energy has values between 2.71.71 eV and 2.93 eV. • The ferroelectric nature of the samples was confirmed using the P - E loop. • Maximum magnetization saturated is observed ~ 13 emu/g. • The maximum microwave frequency has values between 1.39.39 GHz and 2.88 GHz.

Band gap engineered Sn-doped bismuth ferrite nanoparticles for visible light induced ultrafast methyl blue degradation

Remediation of water pollution persists as major concern for scientists and industry. Various ceramic based nanomaterials have been used in efficient photocatalytic degradation of different industrial dyes. However, the major factors that restrict efficacy of these systems are requirement of UV source for activating dye degradation process, prolonged time for degradation and lower efficiency. This paves way to development of alternative material systems that can resolve above problems by not only ensuring maximum dye degradation in minimum time in presence of visible light but also reusability in several cycles. In this work, we report visible light driven photocatalytic degradation of methyl blue (MB) using Sn-doped bismuth ferrite (BFO) nanoparticles. Different concentrations (0, 1%, 1.5%, 2%) of Sn-doped BFO nanoparticles were synthesized using facile sol-gel methods. It was observed that 1.5% Sn-doped BFO nanoparticle exhibits highest photocatalytic activity towards MB degradation compared with pure and other doped BFO nanoparticles. 1.5% Sn-doped BFO nanoparticle delineates 70% dye degradation capability within 10 min of irradiation under visible light. 1.5% Sn-doped sample shows 99% degradation capability within 2 h of visible light irradiation while pristine BFO nanoparticles can degrade only 20% under identical conditions. Additionally, 1.5% Sn-doped BFO nanoparticles are also capable of degrading RhB, another important contaminant. The 1.5% Sn-doped BFO nanoparticle could be a promising photocatalyst for efficient degradation of industrial effluents having various dyes. The efficient dye degradation of 1.5% Sn doped BFO nanoparticle has been explained in terms of increased density of surface active sites evident from bulk structural analyses and greater probability of generation of electron-hole pairs on surface by virtue of reduced band gap. A theoretical modelling of band structure has been done to identify surface .OH ions as most effective species to promote dye degradation.

Enhanced magnetic, dielectric and photoconductive properties of Zr doped BiFeO3 nanostructures

Lead-free ferroelectric BiFe1-xZrxO3 (x = 0.0, 0.015, and 0.025) thin films with varying concentrations of Zr4+ ions were fabricated using nanoparticles synthesized by the hydrothermal method. The X-ray diffraction analysis reveals that the as-synthesized pure and Zr-doped nanoparticles possess distorted rhombohedral structures. The diffraction peak at 32° shifts to the lower angle with increase in Zr content. For higher concentration of Zr4+ ions (2.5% Zr-doped BFO), the impure phase Bi2Fe4O9 evolved and increased the leakage current. Both the SEM and TEM images of pure and doped samples exhibit irregularly shaped clusters of agglomerated nanocrystallites. The SAED pattern of the samples confirms that the samples are highly crystalline and the diffracted rings matched with the lattice planes of single-phase pristine bismuth ferrite (BFO). The Raman E modes of 1.5% Zr-doped BFO nanoparticles are relatively higher in intensity as compared to other samples and exhibited a very weak dependence of dielectric constant on frequency. On comparing, a 1.5% Zr-doped BFO sample showed lowest dielectric constant (∼79) at 1 kHz due to the filling of oxygen vacancies by Zr4+ ions and hence displayed a significant photocurrent of ∼3.10 μA at 5 V. However, for 2.5% Zr dopant concentration, the dielectric constant is quite high at 1 kHz due to the reduction of Fe3+ ion and increased oxygen vacancies; and consequently showed very feeble photocurrent of ∼9.00 nA at 5 V. Furthermore, higher ferromagnetic ordering between Fe3+ and Zr4+ in 2.5% Zr-doped BFO nanostructure has resulted in larger remnant magnetization of 0.585 emu/g. The present study confirms that the optimum concentration of Zr ions substituted at the Fe-site of BiFeO3 reduces the leakage current and improves its photoconductive properties. Besides, the aging problem of BFO nanostructures caused by oxygen vacancies due to the reorientation of dipoles can be significantly reduced through Zr doping. Hence, the enhanced temperature-dependent photo sensing properties of doped BFO nanostructures are more suitable to serve as an active layer in self-powered photodetector systems.

Modification in photovoltaic and photocatalytic properties of bismuth ferrites by tailoring band-gap and ferroelectric properties

Bismuth ferrite has recently been extensively studies as potential material for photovoltaic and photocatalytic applications as it provides wide opportunity to tune band-gap by site engineering with suitable elements. Further, this doping modified the optical and ferroelectric properties of bismuth ferrite for the applications. Rare-earth (Gd) and transition-element (Mn, Co and Cr) co-doped samples of bismuth ferrite have been synthesized by the sol-gel technique at low temperature. Structural characterization using X-ray diffraction reveals a phase transformation from rhombohedral to orthorhombic with co-doping in pure BFO sample. A reduction of grain size for doped bismuth ferrites samples is observed in SEM analysis. The dielectric properties get enhanced with co-doping due to decrease in the Fe2+ ions and oxygen vacancies. Increase in the remnant polarization was obtained in doped BFO samples and maximum Pr∼1.615μC/cm2 for Gd doped BFO sample. Decrease in band-gap values with doping has been observed from (2.35–1.90 eV). Power conversion efficiency has been calculated with doping of different substances which results in improved photovoltaic properties with respect to pure BFO (η% ∼0.00039–0.026). Also, photocatalytic studies have been done for all the samples of BFO. Enhanced values of photocatalytic efficiency (η% ∼90.89–96.08) has been observed with co-doping of rare earth and transition elements in bismuth ferrites. Thus, co-doping of rare-earth and transition-element in bismuth ferrite can improve multiferroic, ferroelectric, photovoltaic and photocatalytic properties for different applications.

Structural and Dielectric Progression of 5 % Gd Doped BiFeO3 Nanoparticles Through Cr (2-8%) Doping

This study reports the structural modifications in undoped multiferroic BiFeO3 (bismuth ferrite or BFO) nanoparticles caused by doping at both the A-site (by 5% Gd) and B-site (by 2-8% Cr) and the resulting improvements in dielectric characteristics. Both un-doped and doped BFO nanoparticles were synthesized using the sol-gel technique and annealed at 600°C for crystallization. X-ray diffractometry (XRD) reveals a phase transition from rhombic (R3c) to orthorhombic (Pn21a). Field Emission Scanning Electron Microscopy (FESEM) study shows the production of nanoparticles with sizes ranging from 80 to 130 nm. Impedance analyzer experiments (100 Hz-10 MHz) show that the dielectric characteristics of doubly doped BFO are very stable over a wide frequency range. The dielectric permittivity of co-doped BFO decreases with Cr doping concentration up to x = 0.06 before reversing. The conductivity drops dramatically as the Cr content rises. Journal of Engineering Science 12(3), 2021, 101-110

Effect of holmium (Ho) partial substitution in structure and ferroelectric properties of bismuth ferrites (BFO)

Multiferroic holmium doped bismuth ferrite samples, prepared by solid-state route method are analyzed in this study to understand the effect of Ho3+ in the crystal structure, thermal properties, dielectric behavior, ferroelectricity, and AC conductivity of bismuth ferrites. Preliminary structural analysis using XRD and refinement characterize to see the distortion in the rhombohedral type of structure with doping. Effect of holmium on morphology, using FESEM and compositional analysis using EDAX show more uniform and dense distribution of well-developed grains as well as a better phase formation with lesser secondary phase, for 80% holmium doped sample. Dielectric, AC conductivity, and impedance parameters variation with frequency and temperature are studied to investigate the electrical behavior of Ho-BFO. Emphasis on the effect of holmium doping on the ferroelectric nature of the doped BFO is further analyzed in terms of P-E loops. The temperature effect on the dielectric properties exhibits an anomaly corresponding to magneto-electric coupling in the samples; all these results are discussed here in detail.

Aspects of Structural and Multiferroic Properties of A- (15% Gd) and B-Site (5–15% Cr) Doped Perovskite BiFeO3 Nanoparticles

This report focuses on the investigation of multiferroic properties of 15% Gd and (5–15) % Cr co-doped Bismuth Ferrite (BFO) nanoparticles prepared by sol–gel method. The synthesized pure BFO has shown to be R3c rhombohedral crystal structure which partially transforms to Pnma orthorhombic crystal structure with increasing Cr dopant in co-doped samples. The crystallite size was found to vary from 68 to 22 nm depending on doping level. SEM images exhibited uniform nanoparticles and the average size of particles was shown to vary from 263 to 114 nm which is comparatively higher than that obtained from XRD results due to agglomeration effects. Ferroelectric tests exhibited a significant reduction in polarization in doped BFO under an applied field of ± 15 kV/cm. In contrast, the magnetic measurement showed a substantial improvement in ferromagnetic properties of the synthesized samples compared to un-doped one. A prominent exchange anisotropy effect was also observed in all the samples at room temperature. In addition, co-doped BFO samples demonstrated a significant reduction in band gap energy from 1.88 to 1.68 eV.

Influence of synthesis, dopants, and structure on electrical properties of bismuth ferrite ($$\hbox {BiFeO}_{3}$$)

Bismuth ferrites (BFO) nanomaterials are one of the promising materials to provide applications in the electrical world for its unique multiferroic properties. The evolution in its research from the pure crystals to doped and co-doped forms has shown mankind the diversity of its properties and subsequent useful applications. The peculiarities of ferroelectric and ferromagnetic properties, as observed in these multiferroics, are the result of the structural perturbations which is due to the nature of the doping element and different synthesis mechanisms. The enhanced magnetoelectric coefficient, high dielectric constant, and improved ferroelectricity of doped BFO open the use in non-volatile memory devices. A consolidation of the noteworthy changes reported in the structural and electrical properties of BFO bulk ceramics, popular category of multiferroics so far is reviewed here in brief. This review mainly focuses on modifications seen in ferroelectric properties with respect to doping at Bismuth site, Iron site, and both or co-doping. As the modifications are mostly due to structural changes, structural and morphological changes occurring due to doping are also covered briefly.

Structural, morphological, optical and dielectric investigations in cobalt doped bismuth ferrite nanoceramics prepared using the sol-gel citrate precursor method

In this work, the synthesis of un-doped and cobalt (Co)-doped nanoceramic samples of bismuth ferrite by cost-effective sol-gel citrate precursor technique are presented. Detailed investigations have been attempted to study the effect of Co substitution on the structural, morphological, dielectric and optical properties of bismuth ferrite prepared using the citrate precursor method. The main feature of these investigations is the relative elimination of secondary phase formation while preparing bismuth ferrite nanoceramic samples. X-ray diffraction analysis shows distorted rhombohedral perovskite structure for all compositions of BiFe1−xCoxO3 (x = 0.00, 0.03, 0.05, 0.10) nanoceramics, where the average crystallite size and induced strain in these samples are calculated using Scherrer’s method and Williamson–Hall equation, respectively. An increasing trend of average crystallite size with increase in dopant concentration was observed. Microstructural examinations of pure and doped BFO identified compact granular shaped microstructures with irregular size and shape but changed to uniform spherical shape after Co substitution up to 10 mol%. Confirmation of the uniform distribution of dopants throughout the sample has been carried out using elemental mapping studies. On the other hand, the chemical states of all the constituent elements were identified by X-ray photoelectron spectroscopic studies. Non-monotonic variations in the real part of dielectric values were observed with increasing Co concentrations. The optical absorption coefficient was found to increase by 35% in 10 mol% Co-doped BFO than that of pure BFO at 480 nm. Optical band gap studies depicted a striking inverse correlation of bandgap values and doping concentration up to 10 mol% Co substitution without varying the intrinsic structural feature of bismuth ferrite. Interestingly, the bandgap value of bismuth ferrite was varied from (2.08 ± 0.02) eV to (1.63 ± 0.02) eV, in the visible region. The results from present investigations suggest that synthesis techniques and chemical substitution need to be continuously optimized to get desired physical properties suitable for device applications such as photovoltaics.

Enhanced electrical conductivity and multiferroic property of cobalt-doped bismuth ferrite nanoparticles

Multiferroic pure and cobalt-doped bismuth ferrite nanoparticles were synthesized by sol–gel method. The X-ray diffraction study showed a distinct crystalline phase with rhombohedral R3c structure. Rietveld refinement confirmed the reduction of crystallite size from 68 to 45 nm in doped BFO. Transmission electron microscopy was performed to confirm the morphology and lattice constant of the pure and cobalt-doped bismuth ferrite nanoparticles. The results of lattice constant have also been compared with the XRD results. Dielectric properties such as resistance, reactance, impedance, and resistivity were significantly decreased in doped BFO to 7.5 MΩ, 14 MΩ, 17 MΩ, 3.7 MΩ-m, respectively, at 100 Hz with concurrent increased conductivity of 0.184 (S/m) × 10–3 at 10 MHz. The ferroelectric properties of pure and doped samples exhibited significantly enhanced maximum polarization and coercive field in doped BFO of 16 µC/cm2 and 6.2 kV/cm, respectively, at an applied field of 15 kV/cm. Ferromagnetic measurements of synthesized cobalt-doped BFO nanoparticles displayed a substantial improvement in saturation magnetization and coercive force of 7.07 emu/gm and 0.9 kOe, respectively. The important enhancement of magnetic properties with moderate value of coercive field of the cobalt-doped samples may have potential applications in spintronics and memory devices.

On the photoelectrochemical performances of rare-earth element doped perovskite thin films deposited by PLD

Herein, we report about an anomalous behavior of the photoelectrochemical (PEC) response of Eu-doped BiFeO3 (BEFO) thin films, as a function of the film’s thickness. The aim of the study was to reveal the water splitting potential of doped BFO with rare-earth Eu element. Heterojunction composed of Eu-BiFeO3 and Nb-SrTiO3 (STON) single crystal substrates were fabricated via pulsed laser deposition technique (PLD). By X-ray diffraction, the crystal structures of all deposited thin films were identified as rhombohedral one, with the out-of-plane axis value as a function of film’s thickness. Optical absorption measurements were carried out for the grown films, an indirect and direct band gaps being identified, with the values for both types of bend-gaps depending on the epitaxial strain. The photoelectrochemical behavior (PEC) was analyzed in respect with the thickness of the deposited BEFO layer. To investigate the PEC performance of the fabricated heterojunctions, the photocurrent density ( Jph ) versus bias potential characteristics in-electrolyte PEC setups has been measured. We have found that the photoelectrochemical response was higher for the BEFO samples as compare with the undoped BFO ones. Moreover, the photocurrent density ( Jph ) is almost independent by the film thickness is ranging from 20 nm to 200 nm, while a significant higher photoelectrochemical response is characterizing the heterojunction based on a 180-200 nm thick BEFO films. These anomalous photoelectrochemical response behavior were analyzed in conjunction with the HR-SEM and scanning electron microscopy (SEM) - room-temperature cathodoluminescence (CL) surface imaging analysis.

Multiferroic properties of La/Er/Mn/Co multi-doped BiFeO3 thin films

Abstract Bi0.9-xLaxEr0.1Fe0.96Co0.02Mn0.02O3 (BLaxEFMCO) thin films were prepared by sol-gel method. The grain size, grain boundary resistance, oxygen vacancies and the amount of Fe2+ of the films were reduced by multi-ion doping to reduce the built-in electric field of the films. An applied voltage was adopted to regulate the effects of the directional alignment of the oxygen vacancies, defects, and defect pairs on the ferroelectric domains at the grain boundaries to control the ferroelectric polarization of the films. Meanwhile, the capacitance peak also reveals the effects of the ferroelectric domains switching, the migration of oxygen vacancies, and the directional alignment of defect pairs on the ferroelectric properties. In addition, the remnant polarization value of the BLa0.01EFMCO thin film reaches 152 μC/cm2, the squareness of the hysteresis loop (Rsq) is calculated to be 1.03, and the maximum switching current is 1.50 mA. The typical butterfly curves under positive and negative electric fields indicate the films with the enhanced ferroelectric properties. Moreover, the BLa0.01EFMCO thin film exhibits the enhanced ferromagnetic properties, and its saturation magnetization (Ms) is 2.32 emu/cm3. Therefore, the ferroelectric properties of the BFO film can be enhanced by the multi-ion doped BFO film to reduce the grain boundary resistance (Rgb), the interface Schottky barrier formed by the asymmetric electrode material at the top and bottom of the film, and the built-in electric field formed by the film internal defect or defect pairs.

Structural, dielectric, ferroelectric and magnetic properties of Gd doped BiFeO3

Gadolinium doped BiFeO3 samples were successfully synthesized by sol–gel method. The X-ray diffraction patterns show the effect of Gd doping in bismuth ferrite on structural changes as well as reduction of impurity phases. Microstructural analysis explores the morphology of pure and Gd doped BiFeO3. M-H plot for doped BFO shows that magnetization reach the value ∼0.20 emu/g. The ferroelectric polarization for applied electric field approaches ∼0.35 μC/cm2 for Bi0.85Gd0.15FeO3. The dielectric data also justified that there is the improvement of dielectric properties of BiFeO3 on doping with Gd.

Ion dopants tuning the interband electronic structure for huge saturated ferroelectric polarization in bismuth ferrite films

Bismuth ferrite (BiFeO3, BFO) as a prototype multiferroic has been extensively studied in past years; however, there are several key issues not to be clearly expressed. Especially, the relationship of structure and physical properties still remains obscure. In this case, the interband electronic structure of BFO was elaborately manipulated by appropriation dopants of Ni and Gd to realize the huge saturated ferroelectric polarization in the polycrystalline films. For instance, a huge saturated polarization PS of 96 μC/cm2 and remnant polarization Pr of 91 μC/cm2 were achieved in Bi0.925Gd0.075Fe0.95Ni0.05O3 film. The results and analysis show that the alteration in the interband electronic structure and the improvement of morphology derived from the ion doping effect indeed play key roles on the improved ferroelectric property of the doped BFO films. The decreased leakage current density and thereby the enhanced ferroelectric polarization in the doped BFO films should be attributed to the decrease in both Fermi level and Urbach energy closely related with the defects, as well as the improved surface uniformity and compactness of the films. Finally, the mechanism and relationship of structure and physical properties in BFO were systemically analyzed and discussed.

Single or both site doped BiFeO3—Which is better candidate for profound electronic device applications?

Magnesium (Mg) and Zirconium (Zr) doped bismuth ferrite (BiFeO3; BFO) such as Bi1−xMgxFeO3 (Mg doped BFO; BMO), BiFe1−xZrxO3 (Zr doped BFO; BZO) and Bi1−xMgxFe1−xZrxO3 (both Mg and Zr doped BFO; BMZO) were synthesized by solid-state reaction techniques with dopant concentrations x = 0 and 0.1, respectively. The distorted rhombohedral structures of doped BFO were confirmed by X-ray diffraction analysis. The microstructural analysis revealed that there were uniform dispersions and homogeneous distributions of ceramics in BMZO as compared to BMO, BZO and pure BFO. The presence of both grain and grain boundary in BMZO indicated its good electrical response than others as evidenced from impedance analysis and in agreement with AC conductivity study. The dielectric and ferroelectric measurement signified that BMZO possessed enhanced dielectric constant and high remanent polarization thus could be a better prominent candidate than others to be used in electronic devices.