Structural phase transition and multiferroic properties of Bi0.8A0.2Fe0.8Mn0.2O3 (A = Ca, Sr) (original) (raw)
Related papers
2013
Here we studied the effect of homovalent Pr 3+ and Y 3+ substitution on the crystal structure, dielectric, electronic polarization and magnetic properties of the BiFeO 3 multiferroic ceramic. The samples were synthesized by the conventional solid-state reaction method. Pure phase formation of Pr doped BiFeO 3 (BFO) has been obtained, while Y 3+ doped BFO has shown a few impurity peaks. It has shown that the crystal structure of the compounds is described within the space group R3c. Pr 3+ modified BFO has shown an anomaly in the ε r vs. T plot around and a Néel temperature 'T N ' ∼ 370 • C. P -E hysteresis loops have shown higher value of remnant polarization for Pr 3+ modified BFO. Magnetic properties of ceramics are determined by the ionic radius of the substituting element. Experimental results propose that the increase in the radius of A-site ion leads to effective suppression of the spiral spin structure of BiFeO 3 , resulting in the appearance of net magnetization.
Structural, magnetic and dielectric properties of Pr-modified BiFeO3 multiferroic
JALCOM (2013)
The structural, vibrational, magnetic and dielectric properties of polycrystalline BiFeO3 and Bi0.95Pr0.05FeO3 are investigated by combining X-ray diffraction, Raman scattering spectra, magnetometry and dielectric measurements. Structural symmetry with rhombohedral R3c phase is revealed for both parent and 5% Pr substitution at Bi site, serving no chemical pressure and causes no structural transition from R3c to any other phase is identified from x-ray diffraction patterns and Raman scattering spectra. The shifting of phonon modes towards higher frequency side is attributed to lower atomic mass of Pr ion as compared to Bi ion. The magnetic measurements at room temperature indicate that Pr substitution induces ferromagnetism and discerns large and non-zero remnant magnetization as compare to pristine BiFeO3. Both dielectric permittivity and loss factor of Bi0.95Pr0.05FeO3 strongly decreases with increased frequency. Significant role of hopping of oxygen ion vacancies in Bi0.95Pr0.05FeO3 is inferred from modulus spectra and ac conductivity analysis.
Effects of Mn doping on structural, dielectric and multiferroic properties of BiFeO 3 nanoceramics
Undoped and Mn doped multiferroic BiFeO 3 nanoparticles were synthesized by sol-gel autocombustion method. Structural studies on the samples were carried out by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, thermogravimetry and Fourier transform infrared spectroscopy techniques. Dielectric and conductivity measurements on the samples have been made in a wide range of frequencies and temperatures. BFO sample exhibits typical dielectric behaviour whereas the Mn doped BFO sample shows anomalous dielectric behaviour which has been attributed to charge carrier hopping mechanisms initiated by structural inhomogeneities and formation of Bi/O vacancies. Ferroelectric and magnetic studies on the samples were made by the corresponding hysteresis loop measurements. The results indicate that the doping of Mn in bismuth sites in the BiFeO 3 , in spite of the enhanced conductivity, has produced considerable improvements both in remnant electric polarization (from 0.0811 to 0.6241 mC/mm 2 ) and saturation magnetization (from 0.53 to 2.54 emu/g) due to the enhanced magnetically driven distortion of spiral spin cycloid by the presence of Mn in mixed valance states. The improved ferroelectric and ferromagnetic properties and the possible magnetoelectric coupling between the ferroic orders of the Mn doped BiFeO 3 makes it suitable for magnetoelectric devices.
NATIONAL CONFERENCE ON PHYSICS AND CHEMISTRY OF MATERIALS: NCPCM2020
We hereby report synthesis and characterizations of BiFeO3 (BFO), Bi0.9La0.1FeO3 (BLFO), Bi0.9La0.1Fe0.9Zn0.1O3 (BLFZO) perovskites. The influence of doping La 3+ at Bi-site and Zn 2+ at Fe-site are investigated in addition to the impurity phases appearing in the synthesized samples. We characterized these samples with X-ray diffraction (XRD) technique to disclose crystal structure acquired. The calculated lattice parameters for BFO, BLFO and BLFZO phases witness the presence of trigonal structure with little variations attributed to varied ionic size of host and guest site ions. The average crystallite size calculated from characteristic peak for BFO, BLFO and BLFZO ceramics were 59.33nm, 81nm and 67.20 nm respectively. From the study of the dielectric nature of these ceramics, it was found that that BLFO exhibits high dielectric constant compared to BFO and BLFZO samples. The loss values of all the samples reported was found relatively very low. The low dielectric constant of BFO and BLFZO in comparison to BLFO can be attributed to the presence of impurity phase with larger fractional percentage. The ac Conductivity study reveals the dc current contribution up to certain field value but in the higher region of applied field, the ac contribution overshadows dc current.
Journal of the American Ceramic Society, 2013
The work presents a comparative study of the effects of divalent Ba, Sr, and Pb substituents on the multiferroic properties of BiFeO3. The multiferroic properties of Bi0.75A0.25FeO3 (A = Sr, Pb, Ba) solid solution have been explained taking into account the effects of size differences and electronic configuration differences between the host element (Bi) and the substituent. X‐ray diffraction studies revealed that Sr and Pb substitution at Bi‐site transforms the rhombohedral phase (R3c) to cubic phase (Pm3m), whereas the Ba‐substituted sample exhibited the presence of both rhombohedral and cubic phases (R3c + Pm3m). Electronic structure studies through XPS revealed that charge imbalance induced by divalent substitution was being compensated by the formation of oxygen vacancies, while the Fe ions exist in Fe2+ and Fe3+ states. Replacement of volatile Bi by Sr, Pb, and Ba reduces the concentration of oxygen vacancies (VO2+) and helps to improve the dielectric properties. Strong magnet...
Journal of Electronic Materials
The multiferroic properties of (1−x)BiFeO3-xBaMnO3 (BBFMO; x = 0.00, 0.05, 0.10, 0.15) solid solutions, prepared by a mechanosynthesis technique, have been investigated. X-ray diffraction analysis showed that all the samples crystallized in the perovskite structure. The presence of infrared absorption bands around 442 cm−1 and 550 cm−1 supports the formation of perovskite structure of the system. Scanning electron microscopy (SEM) studies of the materials at room temperature showed that the average grain size of the samples decreased gradually with increasing BaMnO3 content in the BBFMO system. Detailed studies of impedance parameters revealed that the electrical properties related to the impedance of the solid solutions were strongly dependent on temperature and frequency. Ferroelectric measurements revealed that the electric polarization was significantly enhanced with increasing BaMnO3 content in the solid solution. The room-temperature M-H curves of the samples suggested that, w...
Effect of La doping on dielectric properties of BiFe0.95Mn0.05O3 multiferroics
Ceramics International, 2014
Mn and La co-doped BFO ceramics have been prepared by the sol-gel technique and their dielectric response and the ac conductivity measured as function of frequency in the frequency range from 20 Hz to 2 MHz. The dielectric data has been fitted with the Universal model and the characteristic parameters have been extracted. The maximum potential barrier heights for hopping conduction in these samples have been calculated using Correlated Barrier Hopping model. The Mn doped samples showed improvement in the dielectric constant, however, the dielectric loss, dielectric dispersion and ac conductivity were increased. The ionic space charge has been increased due to substitution of high valence Mn 4 þ ions at Fe 3 þ sites, resulting in high ion-ion coupling and high ac conductivity. The incorporation of La 3 þ at Bi 3 þ sites stabilizes the perovskite structure of BFO ceramic and helps to decrease the oxygen vacancies. Further, it has been found to recover the dielectric response and ac conductivity by reducing the ion-ion coupling in the Mn doped BFO ceramics.
Correlation between structure, oxygen content and the multiferroic properties of Sr doped BiFeO3
Journal of Alloys and Compounds, 2015
In this study a series of Bi 1-x Sr x FeO 3-δ (0≤x≤0.45) multiferroic samples have been prepared in order to study the effect of divalent Sr content on the crystal structure, dielectric and magnetic properties. Rietveld refinement of X-ray diffraction data revealed a structural phase transition from rhombohedral to pseudo cubic phase at x=0.25. Mössbauer measurements showed that Fe ions retained their trivalent state while the Sr 2+ ion substitution at Bi 3+ site results in oxygen deficiency and in tetrahedral coordination for some of the Fe-O ions. For x≥0.25 all the compositions are ferromagnetic with a strong magnetization enhancement between x=0.15 and x=0.25. The ferromagnetic onset is consistent with the structural transformation at x=0.25 that is understood to destroy the parent antiferromagnetic cycloidal spin structure. Oxygen annealing was observed to result in a decrease of the magnetic moment suggesting that oxygen vacancies also contribute to the observed magnetization. The observed decrease in the values of magnetic coercivity at low temperatures is suggested to be indicative of magnetoelectric coupling in these multiferroic samples. The dielectric response depends in general on the crystal structure and oxygen vacancies while the x=0.45 composition shows a marked anomaly in ߝሺܶሻ. This anomaly is explained in terms of relaxation effects originating presumably in nanoscale polar inhomogeneities.
Crystal structure refinement, dielectric and magnetic properties of Sm modified BiFeO3 multiferroic
Journal of Molecular Structure, 2015
SrFe 12 O 19 (SFO), Sr 0.5 Ca 0.5 Fe 12 O 19 (SCFO) and Sr 0.5 Pb 0.5 Fe 12 O 19 (SPFO) hexaferrites have been synthesized by a conventional solid state reaction technique. Powder X-ray diffraction and Rietveld refinement confirm the presence of M-type hexagonal phase in prepared samples. However in SCFO, secondary phase was also present with main phase. Analysis of Nyquist's plots of SFO hexaferrite revealed the contribution of many electrically active regions corresponding to bulk mechanism, distribution of grain boundaries and electrode processes also. Both conductivity and electric modulus formalisms have been employed to study the relaxation dynamics of charge carriers. A perfect overlapping of the normalized plots of modulus isotherms on a single 'super curve' for all the studied temperatures reveals a temperature independence of dynamic processes involved in conduction and for relaxation. In SPFO sample coercivity is reduced effectively but accompanied with increase in magnetization, which is requirement for hexaferrites to be used as magnetic recording media.