R3c Symmetry Research Articles

Structural phase transition from rhombohedral to monoclinic phase and physical properties of (1-x) Bi0.85La0.15FeO3 – (x) Ca0.5Sr0.5TiO3 ceramics prepared by the solid-state route

In the present work, a series of solid solutions were synthesized using the solid-state reaction method for x = 0.0, 0.05, 0.10, and 0.15 in system (1-x)Bi0.85La0.15FeO₃-(x)Ca0.5Sr0.5TiO3 or ((1-x)BLFO-(x)CSTO) ceramics. Structural, optical, dielectric, and ferroelectric properties were studied in detail to investigate the impact of CSTO doping in BFO. Rietveld analysis of X-ray diffraction data of all samples revealed the formation of a single-phase solid solution with a distorted rhombohedral perovskite structure for x = 0.00 and 0.05, characterized by R3c symmetry, a mix of rhombohedral (R3c) and monoclinic (Cc) phases for x = 0.10 (R3c 31 % and Cc 69 %), whereas for x = 0.15 a single-phase solid solution with Cc symmetry was found. UV–visible analysis demonstrated that the optical band gap was increased from 2.11 eV for x = 0.0 to 2.21 eV for x = 0.15 in the visible range, and can be used in photovoltaics applications. The room temperature dielectric properties were measured, and a crucial role of CSTO was revealed in modifying the dielectric properties of BLFO ceramics; the dielectric constant and dielectric loss at 10 kHz change from εr = 82 and tanδ = 0.88 for x = 0.0 to εr = 116 and tanδ = 1.08 for x = 0.15. The leakage current density decreases while increasing the CSTO % from x = 0.0 to 0.15 due to the suppression of oxygen and Bi vacancies, a fact that is further reflected in the ferroelectric properties of CSTO-doped BFO ceramics. Room temperature ferroelectric properties improved with CSTO doping, and Pr was found to be 0.24 μC/cm2, 0.28 μC/cm2, and 0.84 μC/cm2 for x = 0.05, 0.10, and 0.15, respectively.

High-performance electric energy storage in BiFeO3–Ba(Ti0.8Zr0.2)O3 relaxor ferroelectric ceramics

Perovskite relaxor ferroelectrics have been widely developed for energy storage applications due to their exceptional dielectric properties. This work explores the energy storage performance, thermal stability, and structural evolution in (1-x)BiFeO3–x Ba(Ti0.8Zr0.2)O3 ceramics (x = 0.3, 0.4, 0.5, and 0.6) via modulating Ba(Ti0.8Zr0.2)O3 (BZT) concentration. An enhancement of breakdown electric field from 120 kV/cm at x = 0.3–220 kV/cm at x = 0.5 can be attributed to increased grain boundaries and nanodomains as electric barriers to inhibit charge mobility. A high recoverable energy density of 5.9 J/cm3 and a high energy efficiency of 86.2 % were achieved at x = 0.5 and 0.6, respectively. The structure shifts from ferroelectric rhombohedral R3c symmetry toward a coexistence of nonpolar symmetries (including tetragonal P4/mmm, cubic Pm-3m, and orthorhombic Pbnm) with increasing BZT. The integration of BZT in BiFeO3 demonstrates to break the long-range order and promote the formation of polar nanoregions and nanodomains, leading to a high-efficiency energy storage.

Design and electromagnetic shielding of Bi0.5Na0.5TiO3 ceramics as meta-surface absorber for high-frequency microwave application

EMI shielding reduces ambient electromagnetic (EM) radiation by reflecting and absorbing EM waves. Rapid technological growth has increased electronic gadgets and EM radiations, threatening the environment. Microwave materials with high absorption power and cheap cost are crucial for eliminating electromagnetic difficulties in stealth technologies. This study used a conventional solid-state reaction technique to prepare Bi0.5Na0.5TiO3 (BNT) solid solutions and examined their structural, ferroelectric, dielectric, and shielding characteristics. This research describes an EMI shielding material that efficiently absorbs EM wave-induced radiation. Characterizations have been done to evaluate material behavior to support EMI shielding and confirm its absorbing nature. Field emission scanning electron microscopy (FESEM), Raman spectroscopy, and X-ray diffraction (XRD) were employed to examine the surface morphology, local lattice deformation with ionic configuration, and crystal structure. BNT exhibited a rhombohedral structure with R3c symmetry space group with crystallize size 81.5 nm and showed eight Raman active modes with an average grain size of 1.67 μm. The high dielectric constant, reduced dielectric tangent loss, and enhanced polarization value make BNT ceramic a good choice for electrical devices and microwave applications. BNT ceramics showed EMI shielding owing to absorption (SET ∼ −23.65 dB, SEA ∼ −18.91 dB) at 9.2 GHz in the X-band (8.2–12.4 GHz). Meta-surface-based BNT absorbers were designed and simulated in the CST software. The peak depicted the absorption at 9.2 GHz with absorptivity of 91.56 %, 85.03 %, 84.36 %, and 64.6 % for designs 1, 2, 3, and 4, respectively. BNT ceramics have exceptional dielectric absorption properties, and dielectric and magnetic losses, which make them suitable for EMI shielding and absorption applications in the microwave region.

Double perovskite Bi2FeMnO6/TiO2 thin film heterostructure device for neuromorphic computing

Multiferroic materials have important research significance in the fields of magnetic random-access memory, ferroelectric random-access memory, resistive random-access memory, and neuromorphic computing devices due to their excellent and diverse physical properties. In this work, a solution of Bi2FeMnO6 was prepared using a solution-based method, and an Au/Bi2FeMnO6/TiO2 heterostructure device was fabricated on a Si substrate. X-ray diffraction and transmission electron microscopy data indicate that the Bi2FeMnO6 films have hexagonal R3c symmetry structures. The Bi2FeMnO6 film exhibits ferroelectricity with a fine remanent polarization. In addition, the Bi2FeMnO6-based devices have excellent switching ratios of 6.37 × 105. A larger switching ratio can provide a multi-resistance state for the device, which is beneficial for the simulation of synapses. Hence, it effectively emulates excitatory postsynaptic currents, paired-pulse facilitation, and long-term plasticity of synapses and achieves recognition accuracy of 95% in neuromorphic computing. We report a promising material for the development of various nonvolatile memories and neuromorphic synaptic devices.

Crystal structure solution and high-temperature thermal expansion in NaZr2(PO4)3-type materials.

The NaZr2P3O12 family of materials have shown low and tailorable thermal expansion properties. In this study, SrZr4P6O24 (SrO·4ZrO2·3P2O5), CaZr4P6O24 (CaO·4ZrO2·3P2O5), MgZr4P6O24 (MgO·4ZrO2·3P2O5), NaTi2P3O12 [½(Na2O·4TiO2·3P2O5)], NaZr2P3O12 [½(Na2O·4ZrO2·3P2O5)], and related solid solutions were synthesized using the organic-inorganic steric entrapment method. The samples were characterized by in-situ high-temperature X-ray diffraction from 25 to 1500°C at the Advanced Photon Source and National Synchrotron Light Source II. The average linear thermal expansion of SrZr4P6O24 and CaZr4P6O24 was between -1 × 10-6 per°C and 6 ×10-6 per °C from 25 to 1500°C. The crystal structures of the high-temperature polymorphs of CaZr4P6O24 and SrZr4P6O24 with R3c symmetry were solved by Fourier difference mapping and Rietveld refinement. This polymorph is present above ∼1250°C. This work measured thermal expansion coefficients to 1500°C for all samples and investigated the differences in thermal expansion mechanisms between polymorphs and between compositions.

Comparative assessment of structural, magnetic and impedance properties of xLaMnO3-(1-x)BiFeO3 solid solutions

BiFeO3 (BFO) is extensively researched due to its lead-free composition, high ordering temperature, remarkable polarization and useful electric and magnetic switching mechanism for data storage devices. On the other hand, the superexchange ordered system of LaMnO3 (LMO) is well-suited for fuel cells. This study examines the structural, magnetic and impedance properties of xLaMnO3-(1-x)BiFeO3 solid solutions (x = 0.05, 0.10 and 0.20) prepared using the solid state reaction method and sintering. X-ray diffraction technique confirmed single phase material with the hexagonal structure and R3c symmetry. The vibrating sample magnetometer showed the change from antiferromagnetic behaviour of BFO to weak ferromagnetic behaviour of BFO/LMO ceramics and maximum remnantmagnetization of 0.206 emu/g for x = 0.10. The superexchange interactions are responsible for this magnetic behaviour. Impedance analysis was used to investigate the dielectric relaxation and the negative temperature coefficient of resistance.

Inducing a magnetic morphotropic phase boundary in (0.7) BiNdxFeO3-(0.3)BaTiO3 (0 ≤ x ≤ 0.05) system

Multiferroics materials processing ferroelectric and magnetic properties are being explored widely for device applications around the world. Herein, a composite multiferroic material was designed which is expected to show enhanced magnetoelectric (ME) multiferroic properties. In this unique idea, a lead free (0.7)BiFeO3-(0.3)BaTiO3 system with ferroelectric morphotropic phase boundary (MPB) was chosen and a magnetic MPB is induced through Nd incorporation. The MPB was confirmed through X-ray diffraction and Raman studies. The hysteresis loops confirmed the ferroelectric nature of solid solutions and the increase in polarization is related to the induced structural changes. A consistent increase in magnetization with Nd content indicates weaking of R3c symmetry of BiFeO3 due to continuous suppression of the spiral spin structure leading to transition from antiferromagnetic to ferromagnetic response. The presence of ferroelectric and ferromagnetic nature along with the existence of MPB indicates that solid solutions are promising candidates for magnetoelectric multiferroic applications.

Influence of A‐Site Doping on the Local Structure and Magnetic Behavior of BiFeO3 Nanoparticles Investigated by X‐Ray Absorption Fine Structure Spectroscopy

Structural transformation and magnetic change of pure and 1% La/Nd‐doped multiferroic BiFeO3 (BFO) nanoparticles are presented to study the influence of introducing rare‐earth elements at the A‐site in BFO. All samples are successfully produced by the conventional hydrothermal method. Scanning electron microscopy picture demonstrates that doping has an impact on the surface and size of particles, and the magnetic properties of BFO also are improved, even significant ferromagnetism is observed in the Nd‐doped sample. Though the room‐temperature X‐ray diffraction patterns reveal the rhombohedral R3c symmetry for all samples, further identified by the Bi L3‐edge and Fe K‐edge X‐ray absorption fine structure (XAFS) spectra, the nanoscale secondary orthorhombic phase is only detected in Bi0.99Nd0.01FeO3 when analyzing the doped elements according to the La and Nd L3‐edge XAFS spectra. The different magnetic behavior is speculated to be in connection with the orthorhombic symmetry around the Nd atom.

Improved energy-storage performance with superior thermal stability of [(Bi0.5Na0.5)TiO3](1-x) – [Ba(Ni0.5Nb0.5)O3]x relaxor ferroelectric ceramics

Dielectric ceramic capacitors have been extensively investigated in electronic and high-power electrical systems due to their high-power density, fast charge-discharge rates, brilliant fatigue endurance, and good high-temperature stability. In this study, the dielectric and energy-storage performance of [(Bi0.5Na0.5)TiO3](1-x) –[Ba(Ni0.5Nb0.5)O3]x (x = 0, 0.02, 0.03, 0.04, 0.05, and 0.06) relaxor ferroelectric ceramics were investigated as a function of electric field and temperature. The splitting of (200) reflections in the XRD pattern confirmed the rhombohedral phase with R3c symmetry of all samples. The scanning electron microscopy confirmed that the average grain size gradually increased with doping. The introduction of BNN reduced the temperature of the ferroelectric-antiferroelectric phase transition (Td) and antiferroelectric - paraelectric phase and enhanced the relaxor behavior of BNT ceramics. The value of the recoverable energy density (Wrec) and efficiency (η) increased from 0.049 J/cm3 to 0.627 J/cm3 and 2.13%–61.71% with an increase of x from 0 to 0.06. Further, the Wrec values also showed temperature stability with a variation of less than 8% in the range RT-383 K. Hence, the substitution of BNN in BNT positively affects the overall properties and makes it a promising candidate for energy storage application with superior thermal stability.

Thermal Polymorphism in CsCB11H12.

Thermal polymorphism in the alkali-metal salts incorporating the icosohedral monocarba-hydridoborate anion, CB11H12-, results in intriguing dynamical properties leading to superionic conductivity for the lightest alkali-metal analogues, LiCB11H12 and NaCB11H12. As such, these two have been the focus of most recent CB11H12- related studies, with less attention paid to the heavier alkali-metal salts, such as CsCB11H12. Nonetheless, it is of fundamental importance to compare the nature of the structural arrangements and interactions across the entire alkali-metal series. Thermal polymorphism in CsCB11H12 was investigated using a combination of techniques: X-ray powder diffraction; differential scanning calorimetry; Raman, infrared, and neutron spectroscopies; and ab initio calculations. The unexpected temperature-dependent structural behavior of anhydrous CsCB11H12 can be potentially justified assuming the existence of two polymorphs with similar free energies at room temperature: (i) a previously reported, ordered R3 polymorph stabilized upon drying and transforming first to R3c symmetry near 313 K and then to a similarly packed but disordered I43d polymorph near 353 K and (ii) a disordered Fm3 polymorph that initially appears from the disordered I43d polymorph near 513 K along with another disordered high-temperature P63mc polymorph. Quasielastic neutron scattering results indicate that the CB11H12- anions in the disordered phase at 560 K are undergoing isotropic rotational diffusion, with a jump correlation frequency [1.19(9) × 1011 s-1] in line with those for the lighter-metal analogues.

Optimized electric-energy storage in BiFeO3–BaTiO3 ceramics via tailoring microstructure and nanocluster

This study demonstrates the high energy-storage performance using 0.1 wt% MnO2–added 0.7(Bi1−xSmxFeO3)− 0.3(BaTiO3) (x = 0–0.3) ceramics through tailoring microstructures and polar order. Sequential structure transitions were identified from a co-occurrence of nonpolar pseudo-cubic Pm-3m and ferroelectric rhombohedral R3c symmetries to antipolar orthorhombic Pbam and nonpolar orthorhombic Pnma symmetries as Sm substitution increases. Recoverable energy densities (Wrec) of 4.5 J/cm3 and 4.1 J/cm3 with efficiencies (η) of 62.1% and 78.1% were achieved respectively for x = 0.15 and 0.2 at a field of 220 kV/cm. The improved energy storage is associated with microstructure modification and complex grain matrix, consisting of grain boundaries, nanocluster/nanomosaic structures, core-shell structures, and polar nanoregions. The nanocluster/nanomosaic structures may act as barriers to suppress polar order and enhance dielectric breakdown strength. This work provides an efficient route to utilize binary BiFeO3-BaTiO3 ceramics for electrical energy storage.

Origin of Ferroelectricity in BiFeO3-Based Solid Solutions.

We investigate the origin of ferroelectricity in the BiFeO3-LaFeO3 system in rhombohedral R3c and tetragonal P4mm symmetries by ab initio density functional theory calculations and compare their electronic features with paraelectric orthorhombic Pnma symmetry. We show that a coherent accommodation of stereo-active lone pair electrons of Bi is the detrimental factor of ferroelectricity. A Bloch function arising from an indirect Bi_6p-Fe_3d hybridization mediated through O_2p is the primary origin of spontaneous polarization (Ps) in the rhombohedral system. In the orthorhombic system, a similar Bloch function was found, whereas a staggered accommodation of stereo-active lone pair electrons of Bi exclusively results in paraelectricity. A giant Ps reported in the tetragonal system originates from an orbital hybridization of Bi_6p and O_2p, where Fe-3d plays a minor role. The Ps in the rhombohedral system decreases with increasing La content, while that in the tetragonal system displays a discontinuous drop at a certain La content. We discuss the electronic factors affecting the Ps evolutions with La content.

Influence of Ba-doping on the structural and physical properties of Sr2−xBaxFeVO6 double perovskites

The influence of A-site Ba-doping on the structural, dielectric, magnetic, and optical properties of double perovskite (BaxSr2−x)FeVO6 (BSFV(x): x = 0.0–2.0) ceramics prepared by solid-state reaction method, is reported. X-ray diffraction patterns and Rietveld refinements revealed that the BSFV(x) samples with x = 0.0–1.0 crystallized in a cubic crystal structure with an Fm3̅m symmetry whereas the samples with x = 1.5 and 2.0 crystallized in a hexagonal crystal structure with R3c symmetry. Their unit cell volumes increased progressively with the Ba-doping content due to the steric effect generated by the progressive increase of the average ionic radius at A-site, 〈rA〉. SEM images revealed the BSFV(x) samples were highly dense with ceramic grains of polyhedral morphology. Their average grain sizes increased from 2.0(2) μm (x = 0.0) to 5.0(3) μm (x = 2.0). X-ray energy dispersive spectroscopy data gave out the chemical compositions of these samples, which were close to the nominal stoichiometric values. FTIR spectra verified the vibrating modes of the [FeO6] and [VO6] octahedrons in the present samples. XPS spectra confirmed dual chemical valence states of Fe element (Fe2+ and Fe3+) and a triple oxidation states of V element (V3+, V4+ and V5+) as well as two species of oxygens in the BSFV(x) samples. The BSFV ceramics exhibited a strongly frequency-dependent dielectric behavior and a diffuse phase transition, which were resulted from the dielectric response of oxygen vacancies and the electron hopping between the variable cations at B-site as well as the B-site cationic random occupancy. Magnetic Curie temperature (TC) and effective magnetic moment (μeff) decreased as increasing the Ba-doping content due to the weakening of superexchange magnetic interactions between the Fe and V ions. The optical band gaps (Eg) of the BSFV(x) samples extracted from UV-Visible spectra, were in the range of 1.94 – 2.42 eV, exhibiting a blue shift towards semiconductor range as increasing the Ba-doping content. The overlapping between the O-2p and Fe/V-3d orbitals contributes to the Eg in the BSFV samples.

Interplay of multiple structural phase and magnetic response of Bi1-xPrxFeO3 ceramics

The detailed structural phase transition induced by chemical substitution in Bi1-xPrxFeO3 (x = 0.1–0.2) polycrystalline ceramics is reported herein. Pr3+ substitution is observed to destabilize the polar R3c symmetry due to the chemical strain effect caused by the large ionic radius mismatch at the Bi-site. The R3c rhombohedral phase can only be stabilized up to 14 mol% of Pr doping (x < 0.14); the phase transition starts to appear at a higher Pr concentration (x ≥ 0.14), forming a morphotropic phase boundary between the R3c rhombohedral and Pbam orthorhombic phases. Increasing Pr concentration causes the magnetic transition from a pure antiferromagnetic to a weak ferromagnetic state as a result of the evolution of crystal structure. The influence of PB spins on the magnetic properties of Bi1-xPrxFeO3 compounds has been uncovered through manipulation of the mixed phase state by an electric field, temperature, and structural relaxation.

Structural modification and evaluation of dielectric, magnetic and ferroelectric properties of Nd- modified BiFeO3 – PbTiO3 multiferroic ceramics

0.9Bi1- x Nd x FeO3 − 0.1PbTiO3 solid solution with x = 0.05, 0.10, 0.15 and 0.20 were success fully synthesized by the standard solid-state reaction method. The effect of Nd3+ion substitution on structural, micro structural, ferroelectric, magnetic and dielectric properties of 0.9BiFeO3-0.1PbTiO3 have been investigated. The XRD analysis for the samples under study revealed distorted rhombohedral structure with R3C space group. 0.9Bi1- x Nd x FeO3 − 0.1PbTiO3 i.e. (BNFPT)x with x = 0.05, 0.10, 0.15 and 0.20 compounds crystallized as single-phase materials with the same structure as the parent BiFeO3 compound. The SEM study revealed the uniform grain scattering for all prepared samples. Raman spectroscopy showed disappearance of some Raman modes indicated a structural phase transition with substitution of Nd dopants at Bi site and also confirmed the distorted rhombohedral perovskite structure of (BNFPT)x compounds with R3c symmetry. Dielectric measurements reveals that, around Neel temperature, all the samples exhibit magneto-electric coupling and also improved dielectric properties with addition of dopants in BiFeO3(BFO) compound. All the prepared samples exhibit weak ferro-magnetic character at room temperature. However, the variation in linear behavior and enhancement in magnetization is found at 5 K which shows gradual increase in remnant magnetization from 0.00785 emu/g to 0.37513 emu/g with increase in Nd doping for all (BNFPT)x samples. Nd doping reduces leakage current by three orders of magnitude, from 10−4 to 10−7. Ferroelectric study revealed the pinning effect in hysteresis loops with low remnant polarization and coercive field which can be related to the energy storage performance of the samples.

Enhanced electromagnetic interference (EMI) shielding in BiFeO3–graphene oxide nanocomposites over X-band frequency region

BiFeO3–graphene oxide (BFO–GO) nanocomposites were synthesized through ultra-sonication under mild heating, and their electromagnetic interference (EMI) shielding performance was investigated. The nanocomposites preserve the crystalline phase with R3c symmetry as analyzed by Rietveld refinement of x-ray diffraction data. The Raman spectroscopy and x-ray photoelectron spectroscopy studies confirm the formation of structured GO in nanocomposites samples. Magnetic hysteresis curves indicate unsaturated magnetic behavior. The interfacial polarization is dominating in BFO–GO composites as estimated from frequency dependent complex parameters determined in line with the Nicolson–Ross–Weir algorithm. The BFO–GO nanocomposites showed EMI shielding effectiveness of 18 dB (93% attenuation) over the measured frequency range. The oxide composite is a suitable EMI shielding material for techno-commercial applications.

The effect of La doping on multiferroic BiFeO3 ceramic through structural, dielectric, magnetic, ferroelectric, and optical studies

In this study, La-doped bismuth ferrite (BLFO), Bi1-xLaxFeO3 (x = 0.00, 0.005, 0.007, 0.01) compositions have been synthesized via a solid-state method to investigate their structural, electrical, magnetic, ferroelectric, and optical properties. All the synthesized ceramics were found to be in rhombohedral distorted perovskite structures with R3c symmetry. A significantly reduced grain size with improved dielectric properties (enhanced dielectric constant and reduced dielectric loss) was observed with La doping up to composition x = 0.007. The magnetization study revealed that substitution of La in BFO enhances remnant magnetization (Mr) and coercive field (Hc). The ferroelectric study manifested that composition x = 0.007 retained a higher polarization value among all the ceramics. Moreover, the optical study exhibited that with doping, the bandgap increased from 2.49 eV for BFO to 2.64 for x = 0.007 ceramic. For the last composition x = 0.01, the bandgap decreased to 2.43 eV, which can be advantageous for magnetic photocatalysts applications.

Effective bandgap tuning with non-trivial modulation in room temperature magnetic and electrical responses of low level Ba–Cr co-substituted BiFeO3 nanoparticles

This work reports the effects of low-level Ba(5%)-Cr(1–5%) co-incorporation on room temperature structural and functional properties of sol-gel synthesized bismuth ferrite (BiFeO3) nanoparticles. Within this co-substitution limit, structural stability of the main perovskite phase with rhombohedral (R3c) symmetry was enhanced by Ba substitution. The defect chemical and crystallographic modifications together brought about by the low level co-substitution considerably reduced the BiFeO3 nanoparticle's optical bandgap by ∼23% to 1.59 eV. An enhanced saturation magnetization (∼3.6 emu/g) observed in BiFeO3 was further raised by ∼ 100% through 5% Ba–Cr co-incorporation. This significant improvement in the magnetic property of the materials, recognized to be composed of single domain non-interacting nanoparticles was attributed to an enhanced super-exchange interaction phenomenon, and was further corroborated by the contributions from the deconvoluted magnetic components associated with different microstructural phases. The defect assisted variation in leakage current culminates in lossy dielectric type polarization-hysteresis responses. The origin of the leakage current was analyzed in terms ohmic, SCLC and Pool-Frankel emission mechanisms. Technically these observed developments in the functional responses of low level Ba–Cr co-substituted BiFeO3 nanoparticles, brought about by the structural and microstructural modifications open a potential window for photo-chemical/electric and magnetic applications.

Stability of rhombohedral structure and improved dielectric and ferroelectric properties of Ba, Na, Ti doped BiFeO3 solid solutions

A study of the (1-x)BiFeO 3 -(x)Ba 1/2 Na 1/2 TiO 2.75 (BFO-BNT) solid solutions obtained using the solid state reaction method, for different molar relative concentration of Ba 1/2 Na 1/2 TiO 2.75 in the 0.0 ≤ x ≤ 0.12 composition range, is presented. The crystal structure and the dielectric and ferroelectric properties are studied in detail. Results of the Rietveld refinement of the X-ray diffraction data demonstrate that the system is single phase with R3c symmetry up to x = 0.09 while for x = 0.12, a small quantity of a secondary phase with P4mm symmetry appears. Scanning electron microscopy demonstrates that BNT presence promotes grain growth resulting in larger grains. Raman spectroscopy shows that, with increasing x, some of the A and E Raman modes slightly reduce their intensity while shifting in frequency, evincing the structural changes caused by the Ba, Na, and Ti incorporation on the BFO lattice. The X-ray photoelectron spectroscopy study confirms the successful substitution and gradual structural distortion in the samples. The improvement in dielectric properties with increasing BNT concentration can be attributed to stable dipole moment formation. Compared with pure BFO ceramics, doped BFO samples exhibit remarkably enhanced ferroelectric properties.

Crystal structure, dielectric and magnetic properties of xBaFe12O19-(1 − x)Na0.5Bi0.5TiO3 composites

Multiferroic composites xBaFe12O19-(1 − x)Na0.5Bi0.5TiO3 were synthesized. Rietveld analysis of XRD patterns of confirms the coexistence of hexagonal (P63/mmc) and rhombohedral (R3c) symmetry. SEM micrographs depict that the average grain size of composites decreases with increase in ferrite phase. The variations of dielectric constant (ε′) and dielectric loss (tanδ) were examined as a function of frequency and at different temperatures. ε′ and tanδ show the dispersion behavior at lower frequencies and become independent at higher frequencies. The magnetic assessment of these composites carried by analyzing M-H hysteresis loop reveals their hard magnetic behavior.