Single phase Bi0.80La0.15A0.05FeO3-δ (A = Ca, Sr,Ba) dense ceramics were synthesized via solid
s... more Single phase Bi0.80La0.15A0.05FeO3-δ (A = Ca, Sr,Ba) dense ceramics were synthesized via solid state reaction method. Structural studies through X-ray diffraction shows that all prepared ceramics crystallized in a rhombohedrally (R3C) distorted BiFeO3 structure with compressive lattice distortion induced by the rare earth (La3+) ion and divalent co-doping at the Bi-site for the Raman study. Scanning electron micrograph of the compounds showed the uniform distribution of grains on the sample surface with high density. A large ferromagnetic hysteresis loop is observed for La/Ba co-doped BiFeO3 as compared with BiFeO3 prepared under similar conditions, with saturation magnetization of 6.85 emu/g and remnant magnetization of 2.72 emu/g at 300K. Clear ferromagnetic ground state was observed in Bi0.80La0.15Ba0.05FeO3 and weak ferromagnetism in BLCFO and BLSFO samples. Dielectric constant and dielectric loss were found to decrease with increase in frequency for all the compounds. These improved properties of La/Ba co-doped BFO demonstrate the possibility of enhancing the magnetic applicability and makes very promising for industrial applications such as new devices in information storage.
We report the phonon structure of Bi2Fe4O9 ceramics as synthesized by solid-state reaction route.... more We report the phonon structure of Bi2Fe4O9 ceramics as synthesized by solid-state reaction route. Rietveld refined X-ray diffraction patterns confirmed the formation of single-phase perovskite structure and all the peaks of Bi2Fe4O9 perfectly indexed to the orthorhombic (space group Pbam). Raman scattering measurements identifies 12Ag+1B2g+1B3g Raman active optical phonon modes. Apart from phonon scattering, mode at 470 cm−1 is observed which is due to magnon scattering. The P-E loop infers paraelectric nature of Bi2Fe4O9.
Raman scattering measurements were made on polycrystalline CoFe2O4 and Co0.5Ni0.5Fe2O4 ferrites a... more Raman scattering measurements were made on polycrystalline CoFe2O4 and Co0.5Ni0.5Fe2O4 ferrites as prepared by solid-state reaction route. Rietveld refined X-ray diffraction pattern confirmed the formation of single-phase and both of the samples perfectly indexed in cubic spinel structure with Fd3m space group. Slight reduction in the lattice parameter of Co0.5Ni0.5Fe2O4 has been observed as compared to CoFe2O4. From Raman scattering spectra, a shoulder like feature has been observed in both of the compounds reveals that octahedral site is occupied by Co, Ni and Fe ions and tetrahedral site is occupied by only Fe ion.
Single-phase polycrystalline samples of Bi0.8Nd0.2-xCaxFeO3 (x = 0.0, 0.1) were synthesized by ch... more Single-phase polycrystalline samples of Bi0.8Nd0.2-xCaxFeO3 (x = 0.0, 0.1) were synthesized by chemical coprecipitation method. X-ray diffraction patterns accompanied by Rietveld–refined crystal structure parameters reveal the phase transition of Bi0.8Nd0.1Ca0.1FeO3 with rhombohedral R3c symmetry to triclinic structure of Bi0.8Nd0.2FeO3 sample. Frequency dependence of dielectric constant (e’) and dielectric loss (tand), infers enhancement of both e’ (tand) in narrow band gap of Nd/Ca co-doped BFO as compare to wide band pristine BFO.
Bulk samples of spinel ferrites with the compositional formula, Co1xNixFe2O4 (x¼0.0, 0.5, 1.0) w... more Bulk samples of spinel ferrites with the compositional formula, Co1xNixFe2O4 (x¼0.0, 0.5, 1.0) were synthesized by a solid-state reaction route to discuss doping effect on the structural, vibrational and dielectric properties. The crystal structure and cell parameters were refined by the Rietveld analysis, infers that ceramics crystallized in single-phase cubic structure with Fd-3m space group. The variation in cell parameters with Ni substitution confirmed the partial substitution of the Co3þ by Ni3þ into the spinel CoFe2O4 structure. A blue shift in Ni doped CoFe2O4 ferrite has been observed as compared to parent CoFe2O4 from Raman scattering measurements. The dielectric constant (ε0) and loss tangent (tan δ) have been investigated as a function of composition and frequency in the frequency range 10 Hz–1 MHz. Porous ceramics are useful for microelectronics with lower value of dielectric constant.
The effect of Nd doping on Bi1−xNdxFeO3 (x = 0.0, 0.175, 0.20) multiferroics synthesized by chemi... more The effect of Nd doping on Bi1−xNdxFeO3 (x = 0.0, 0.175, 0.20) multiferroics synthesized by chemical co-precipitation method has been investigated by Rietveld analysis of X-ray powder diffraction (XRD) data. The formations of the single-phase compounds were confirmed by XRD. X-ray diffraction along with the Rietveld-refinement showed a gradual change in crystal structure from rhombohedral to triclinic with increasing Nd doping concentration. The bond distances along with bond angles between atoms for all the compounds were calculated which supports the structural results. Raman spectroscopy also recommends a structural change and is accompanied by the weakening of long-range ferroelectric order with increasing doping concentration (x). The results of Raman spectra for BiFeO3 (BFO) match well with the earlier reported bulk ceramic and epitaxially grown thin film of BFO. The ferroelectric-paraelectric transition in 20% Nd BFO substituted was explained according to the change of Bi–O covalent bond as a result of decline of stereochemical activity of Bi lone pair electron and is further confirmed through ferroelectric polarization (P–E) hysteresis loop.
In this paper, we report the variations in the crystal structure, average crystallite size, Raman... more In this paper, we report the variations in the crystal structure, average crystallite size, Raman spectra and magnetic properties of ZnxMn1−xFe2O4 (x = 0.0, 0.25, 0.5, 0.75, 1.0) mixed ferrite samples synthesized by chemical co-precipitation method. The X-ray diffraction pattern confirms that the mixed ferrite samples are in cubic inverse spinel structure, which is further validated by Rietveld refinement. The oxygen position, the lattice parameter, and the cation distribution have been determined by means of Rietveld analysis, indicating the existence of mixed ferrites in all samples. The final structure was refined in space group Fd3m. The structural studies identify the decrease of lattice parameter, whereas the crystallite size increases and porosity decreases on increasing the Zn concentration. IR spectra confirm vibration of Fe2+–O2− bond at tetrahedral (A) site. The Raman spectrum reveals active phonon modes at room temperature and shifting of modes toward the higher frequency side on moving from MnFe2O4 to ZnFe2O4. The transmission Mössbauer spectroscopy determines the site preference of the substituted ions and their effect on the hyperfine magnetic fields. The results showed that all the samples are superparamagnetic in nature.
The influence of the Zn and Mg content on the structural and magnetic properties of cubic cobalt ... more The influence of the Zn and Mg content on the structural and magnetic properties of cubic cobalt ferrites (CoFe2O4) synthesized by chemical co-precipitation method was investigated using X-ray powder diffraction
(XRD), Raman spectroscopy and vibrating sample magnetometer (VSM). Rietveld – refined X-ray powder diffraction patterns at room temperature confirmed the formation of single-phase cubic (FCC) structure with Fd3m space group for all prepared samples. Slight variation in the lattice parameter of Mg doped CoFe2O4 has been observed. Raman analysis reveals the doublet like nature of A1g mode for all synthesized samples. Small shift in Raman modes and increment in the linewidth has been observed with the doping ions. The magnetic measurement explored that the saturation value (Ms) is maximum for CoFe2O4 as compared to Zn and Mg doped cobalt ferrites samples.
Polycrystalline Bi0.95Pr0.05FeO3 was synthesized by conventional two-step sintering method to stu... more Polycrystalline Bi0.95Pr0.05FeO3 was synthesized by conventional two-step sintering method to study the structural properties. X-ray diffraction patterns confirmed the formation of single-phase perovskite structure. Rietveld–refined crystal structure parameters revealed the existence of rhombohedral R3c symmetry in the prepared sample. Raman spectrum identifies the eleven active optical phonon modes. The doped sample shows a blue shift in Raman modes as compared to pure BiFeO3. The shifting towards higher energy frequencies or blue shift is due to the doping of light mass Pr3+ ion for Bi3+
Multiferroic Bi0.9Ca0.1Fe0.9Co0.1O3 [BCFCO] nanoparticles of 23 nm were successfully prepared by ... more Multiferroic Bi0.9Ca0.1Fe0.9Co0.1O3 [BCFCO] nanoparticles of 23 nm were successfully prepared by chemical co-precipitation method. The x-ray diffraction patterns confirmed the formation of single-phase perovskite structure. Rietveld–refinement of crystal structure parameters revealed the existence of rhombohedral R3c symmetry. Raman spectrum identifies the five active optical phonon modes (A1-2, E-2, A1-4, E-8, E-9). The BCFCO nanomaterials sample shows the lower frequency shift in Raman modes as compared to pure BiFeO3and is attributed to the structural distortion
at Fe site
Journal of Moleculer Structure (Elsevier), Feb 2013
The effect of Sr2+ doping on Bi1-xSrxFeO3 (x = 0.0, 0.15, 0.175, 0.25) multiferroic ceramics synt... more The effect of Sr2+ doping on Bi1-xSrxFeO3 (x = 0.0, 0.15, 0.175, 0.25) multiferroic ceramics synthesized by citrate sol-gel method has been investigated by Rietveld analysis of X-ray powder diffraction data, Raman spectroscopy and dielectric measurement. X-ray diffraction along with the Rietveld–refinement showed a gradual change in crystal structure from rhombohedral (R3c) to pseudotetragonal (P4/mmm) with enhanced divalent Sr2+ ion concentration. All the 13 Raman modes predicted by group theory (ΓR3c = 4 A1 + 9 E) for R3c structure of Bi1-xSrxFeO3 (x = 0.0, 0.15, 0.175, 0.25) were observed in the present study. The A1-2 and E-4 modes are completely suppressed, while to that A1-3, E-8 mode in Bi1-xSrxFeO3 (x = 0.175, 0.25) and E-2, E-5, and E-8 modes (x = 0.25) disappear completely as compared to parent BFO. The structural phase transition and weakening of long-range ferroelectric order with increasing doping concentration are thus further confirmed from Raman scattering spectra. The dielectric anomaly has been occurred in dielectric constant and dielectric loss near 325 °C, 305 °C, 270 °C and 250 °C (f = 10 kHz) in BiFeO3, Bi0.85Sr0.15FeO3, Bi0.825Sr0.175FeO3 and Bi0.75Sr0.25FeO3, respectively.
Polycrystalline Bi1−xBaxFe1−yMyO3 (M = Co and Mn; x = 0.1, y = 0.1) were synthesized by solid-sta... more Polycrystalline Bi1−xBaxFe1−yMyO3 (M = Co and Mn; x = 0.1, y = 0.1) were synthesized by solid-state route method to study the compositional driven structural transformations in multiferroics. Room temperature X-ray diffraction patterns confirmed the formation of perovskite structure. Rietveld-refined crystal structure parameters revealed the existence of rhombohedral R3c symmetry for both the samples. The samples were found to be nearly free from any other secondary phases. Raman analysis reveals that Ba atom substitutes Bi site and Mn and Co atom substitutes Fe site into the BiFeO3 with the shifting of phonon modes. The red shift is attributed to Co or Mn doping where as blue shift occurs from Ba doping. The differential scanning calorimetry reveals the corresponding Neel temperature 370 °C and 326 °C for Co and Mn doped samples. Ba and Co substitution with x = 0.1 and y = 0.1 has not affected the Neel temperature of the parent BiFeO3 as well of Ba and Mn substitution. The variation of frequency dispersion in permittivity and loss pattern due to A-site and B-site substitution in BiFeO3 was observed in the dielectric response curve.
Single phase Bi0.80La0.15A0.05FeO3-δ (A = Ca, Sr,Ba) dense ceramics were synthesized via solid
s... more Single phase Bi0.80La0.15A0.05FeO3-δ (A = Ca, Sr,Ba) dense ceramics were synthesized via solid state reaction method. Structural studies through X-ray diffraction shows that all prepared ceramics crystallized in a rhombohedrally (R3C) distorted BiFeO3 structure with compressive lattice distortion induced by the rare earth (La3+) ion and divalent co-doping at the Bi-site for the Raman study. Scanning electron micrograph of the compounds showed the uniform distribution of grains on the sample surface with high density. A large ferromagnetic hysteresis loop is observed for La/Ba co-doped BiFeO3 as compared with BiFeO3 prepared under similar conditions, with saturation magnetization of 6.85 emu/g and remnant magnetization of 2.72 emu/g at 300K. Clear ferromagnetic ground state was observed in Bi0.80La0.15Ba0.05FeO3 and weak ferromagnetism in BLCFO and BLSFO samples. Dielectric constant and dielectric loss were found to decrease with increase in frequency for all the compounds. These improved properties of La/Ba co-doped BFO demonstrate the possibility of enhancing the magnetic applicability and makes very promising for industrial applications such as new devices in information storage.
We report the phonon structure of Bi2Fe4O9 ceramics as synthesized by solid-state reaction route.... more We report the phonon structure of Bi2Fe4O9 ceramics as synthesized by solid-state reaction route. Rietveld refined X-ray diffraction patterns confirmed the formation of single-phase perovskite structure and all the peaks of Bi2Fe4O9 perfectly indexed to the orthorhombic (space group Pbam). Raman scattering measurements identifies 12Ag+1B2g+1B3g Raman active optical phonon modes. Apart from phonon scattering, mode at 470 cm−1 is observed which is due to magnon scattering. The P-E loop infers paraelectric nature of Bi2Fe4O9.
Raman scattering measurements were made on polycrystalline CoFe2O4 and Co0.5Ni0.5Fe2O4 ferrites a... more Raman scattering measurements were made on polycrystalline CoFe2O4 and Co0.5Ni0.5Fe2O4 ferrites as prepared by solid-state reaction route. Rietveld refined X-ray diffraction pattern confirmed the formation of single-phase and both of the samples perfectly indexed in cubic spinel structure with Fd3m space group. Slight reduction in the lattice parameter of Co0.5Ni0.5Fe2O4 has been observed as compared to CoFe2O4. From Raman scattering spectra, a shoulder like feature has been observed in both of the compounds reveals that octahedral site is occupied by Co, Ni and Fe ions and tetrahedral site is occupied by only Fe ion.
Single-phase polycrystalline samples of Bi0.8Nd0.2-xCaxFeO3 (x = 0.0, 0.1) were synthesized by ch... more Single-phase polycrystalline samples of Bi0.8Nd0.2-xCaxFeO3 (x = 0.0, 0.1) were synthesized by chemical coprecipitation method. X-ray diffraction patterns accompanied by Rietveld–refined crystal structure parameters reveal the phase transition of Bi0.8Nd0.1Ca0.1FeO3 with rhombohedral R3c symmetry to triclinic structure of Bi0.8Nd0.2FeO3 sample. Frequency dependence of dielectric constant (e’) and dielectric loss (tand), infers enhancement of both e’ (tand) in narrow band gap of Nd/Ca co-doped BFO as compare to wide band pristine BFO.
Bulk samples of spinel ferrites with the compositional formula, Co1xNixFe2O4 (x¼0.0, 0.5, 1.0) w... more Bulk samples of spinel ferrites with the compositional formula, Co1xNixFe2O4 (x¼0.0, 0.5, 1.0) were synthesized by a solid-state reaction route to discuss doping effect on the structural, vibrational and dielectric properties. The crystal structure and cell parameters were refined by the Rietveld analysis, infers that ceramics crystallized in single-phase cubic structure with Fd-3m space group. The variation in cell parameters with Ni substitution confirmed the partial substitution of the Co3þ by Ni3þ into the spinel CoFe2O4 structure. A blue shift in Ni doped CoFe2O4 ferrite has been observed as compared to parent CoFe2O4 from Raman scattering measurements. The dielectric constant (ε0) and loss tangent (tan δ) have been investigated as a function of composition and frequency in the frequency range 10 Hz–1 MHz. Porous ceramics are useful for microelectronics with lower value of dielectric constant.
The effect of Nd doping on Bi1−xNdxFeO3 (x = 0.0, 0.175, 0.20) multiferroics synthesized by chemi... more The effect of Nd doping on Bi1−xNdxFeO3 (x = 0.0, 0.175, 0.20) multiferroics synthesized by chemical co-precipitation method has been investigated by Rietveld analysis of X-ray powder diffraction (XRD) data. The formations of the single-phase compounds were confirmed by XRD. X-ray diffraction along with the Rietveld-refinement showed a gradual change in crystal structure from rhombohedral to triclinic with increasing Nd doping concentration. The bond distances along with bond angles between atoms for all the compounds were calculated which supports the structural results. Raman spectroscopy also recommends a structural change and is accompanied by the weakening of long-range ferroelectric order with increasing doping concentration (x). The results of Raman spectra for BiFeO3 (BFO) match well with the earlier reported bulk ceramic and epitaxially grown thin film of BFO. The ferroelectric-paraelectric transition in 20% Nd BFO substituted was explained according to the change of Bi–O covalent bond as a result of decline of stereochemical activity of Bi lone pair electron and is further confirmed through ferroelectric polarization (P–E) hysteresis loop.
In this paper, we report the variations in the crystal structure, average crystallite size, Raman... more In this paper, we report the variations in the crystal structure, average crystallite size, Raman spectra and magnetic properties of ZnxMn1−xFe2O4 (x = 0.0, 0.25, 0.5, 0.75, 1.0) mixed ferrite samples synthesized by chemical co-precipitation method. The X-ray diffraction pattern confirms that the mixed ferrite samples are in cubic inverse spinel structure, which is further validated by Rietveld refinement. The oxygen position, the lattice parameter, and the cation distribution have been determined by means of Rietveld analysis, indicating the existence of mixed ferrites in all samples. The final structure was refined in space group Fd3m. The structural studies identify the decrease of lattice parameter, whereas the crystallite size increases and porosity decreases on increasing the Zn concentration. IR spectra confirm vibration of Fe2+–O2− bond at tetrahedral (A) site. The Raman spectrum reveals active phonon modes at room temperature and shifting of modes toward the higher frequency side on moving from MnFe2O4 to ZnFe2O4. The transmission Mössbauer spectroscopy determines the site preference of the substituted ions and their effect on the hyperfine magnetic fields. The results showed that all the samples are superparamagnetic in nature.
The influence of the Zn and Mg content on the structural and magnetic properties of cubic cobalt ... more The influence of the Zn and Mg content on the structural and magnetic properties of cubic cobalt ferrites (CoFe2O4) synthesized by chemical co-precipitation method was investigated using X-ray powder diffraction
(XRD), Raman spectroscopy and vibrating sample magnetometer (VSM). Rietveld – refined X-ray powder diffraction patterns at room temperature confirmed the formation of single-phase cubic (FCC) structure with Fd3m space group for all prepared samples. Slight variation in the lattice parameter of Mg doped CoFe2O4 has been observed. Raman analysis reveals the doublet like nature of A1g mode for all synthesized samples. Small shift in Raman modes and increment in the linewidth has been observed with the doping ions. The magnetic measurement explored that the saturation value (Ms) is maximum for CoFe2O4 as compared to Zn and Mg doped cobalt ferrites samples.
Polycrystalline Bi0.95Pr0.05FeO3 was synthesized by conventional two-step sintering method to stu... more Polycrystalline Bi0.95Pr0.05FeO3 was synthesized by conventional two-step sintering method to study the structural properties. X-ray diffraction patterns confirmed the formation of single-phase perovskite structure. Rietveld–refined crystal structure parameters revealed the existence of rhombohedral R3c symmetry in the prepared sample. Raman spectrum identifies the eleven active optical phonon modes. The doped sample shows a blue shift in Raman modes as compared to pure BiFeO3. The shifting towards higher energy frequencies or blue shift is due to the doping of light mass Pr3+ ion for Bi3+
Multiferroic Bi0.9Ca0.1Fe0.9Co0.1O3 [BCFCO] nanoparticles of 23 nm were successfully prepared by ... more Multiferroic Bi0.9Ca0.1Fe0.9Co0.1O3 [BCFCO] nanoparticles of 23 nm were successfully prepared by chemical co-precipitation method. The x-ray diffraction patterns confirmed the formation of single-phase perovskite structure. Rietveld–refinement of crystal structure parameters revealed the existence of rhombohedral R3c symmetry. Raman spectrum identifies the five active optical phonon modes (A1-2, E-2, A1-4, E-8, E-9). The BCFCO nanomaterials sample shows the lower frequency shift in Raman modes as compared to pure BiFeO3and is attributed to the structural distortion
at Fe site
Journal of Moleculer Structure (Elsevier), Feb 2013
The effect of Sr2+ doping on Bi1-xSrxFeO3 (x = 0.0, 0.15, 0.175, 0.25) multiferroic ceramics synt... more The effect of Sr2+ doping on Bi1-xSrxFeO3 (x = 0.0, 0.15, 0.175, 0.25) multiferroic ceramics synthesized by citrate sol-gel method has been investigated by Rietveld analysis of X-ray powder diffraction data, Raman spectroscopy and dielectric measurement. X-ray diffraction along with the Rietveld–refinement showed a gradual change in crystal structure from rhombohedral (R3c) to pseudotetragonal (P4/mmm) with enhanced divalent Sr2+ ion concentration. All the 13 Raman modes predicted by group theory (ΓR3c = 4 A1 + 9 E) for R3c structure of Bi1-xSrxFeO3 (x = 0.0, 0.15, 0.175, 0.25) were observed in the present study. The A1-2 and E-4 modes are completely suppressed, while to that A1-3, E-8 mode in Bi1-xSrxFeO3 (x = 0.175, 0.25) and E-2, E-5, and E-8 modes (x = 0.25) disappear completely as compared to parent BFO. The structural phase transition and weakening of long-range ferroelectric order with increasing doping concentration are thus further confirmed from Raman scattering spectra. The dielectric anomaly has been occurred in dielectric constant and dielectric loss near 325 °C, 305 °C, 270 °C and 250 °C (f = 10 kHz) in BiFeO3, Bi0.85Sr0.15FeO3, Bi0.825Sr0.175FeO3 and Bi0.75Sr0.25FeO3, respectively.
Polycrystalline Bi1−xBaxFe1−yMyO3 (M = Co and Mn; x = 0.1, y = 0.1) were synthesized by solid-sta... more Polycrystalline Bi1−xBaxFe1−yMyO3 (M = Co and Mn; x = 0.1, y = 0.1) were synthesized by solid-state route method to study the compositional driven structural transformations in multiferroics. Room temperature X-ray diffraction patterns confirmed the formation of perovskite structure. Rietveld-refined crystal structure parameters revealed the existence of rhombohedral R3c symmetry for both the samples. The samples were found to be nearly free from any other secondary phases. Raman analysis reveals that Ba atom substitutes Bi site and Mn and Co atom substitutes Fe site into the BiFeO3 with the shifting of phonon modes. The red shift is attributed to Co or Mn doping where as blue shift occurs from Ba doping. The differential scanning calorimetry reveals the corresponding Neel temperature 370 °C and 326 °C for Co and Mn doped samples. Ba and Co substitution with x = 0.1 and y = 0.1 has not affected the Neel temperature of the parent BiFeO3 as well of Ba and Mn substitution. The variation of frequency dispersion in permittivity and loss pattern due to A-site and B-site substitution in BiFeO3 was observed in the dielectric response curve.
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state reaction method. Structural studies through X-ray diffraction shows that all prepared ceramics
crystallized in a rhombohedrally (R3C) distorted BiFeO3 structure with compressive lattice distortion
induced by the rare earth (La3+) ion and divalent co-doping at the Bi-site for the Raman study. Scanning
electron micrograph of the compounds showed the uniform distribution of grains on the sample surface
with high density. A large ferromagnetic hysteresis loop is observed for La/Ba co-doped BiFeO3 as
compared with BiFeO3 prepared under similar conditions, with saturation magnetization of 6.85 emu/g
and remnant magnetization of 2.72 emu/g at 300K. Clear ferromagnetic ground state was observed in
Bi0.80La0.15Ba0.05FeO3 and weak ferromagnetism in BLCFO and BLSFO samples. Dielectric constant and
dielectric loss were found to decrease with increase in frequency for all the compounds. These improved
properties of La/Ba co-doped BFO demonstrate the possibility of enhancing the magnetic applicability
and makes very promising for industrial applications such as new devices in information storage.
refined X-ray diffraction patterns confirmed the formation of single-phase perovskite structure and all the peaks of
Bi2Fe4O9 perfectly indexed to the orthorhombic (space group Pbam). Raman scattering measurements identifies
12Ag+1B2g+1B3g Raman active optical phonon modes. Apart from phonon scattering, mode at 470 cm−1 is observed
which is due to magnon scattering. The P-E loop infers paraelectric nature of Bi2Fe4O9.
prepared by solid-state reaction route. Rietveld refined X-ray diffraction pattern confirmed the formation of single-phase
and both of the samples perfectly indexed in cubic spinel structure with Fd3m space group. Slight reduction in the lattice
parameter of Co0.5Ni0.5Fe2O4 has been observed as compared to CoFe2O4. From Raman scattering spectra, a shoulder like
feature has been observed in both of the compounds reveals that octahedral site is occupied by Co, Ni and Fe ions and
tetrahedral site is occupied by only Fe ion.
method. X-ray diffraction patterns accompanied by Rietveld–refined crystal structure parameters reveal the
phase transition of Bi0.8Nd0.1Ca0.1FeO3 with rhombohedral R3c symmetry to triclinic structure of Bi0.8Nd0.2FeO3 sample.
Frequency dependence of dielectric constant (e’) and dielectric loss (tand), infers enhancement of both e’ (tand) in
narrow band gap of Nd/Ca co-doped BFO as compare to wide band pristine BFO.
route to discuss doping effect on the structural, vibrational and dielectric properties. The crystal structure and cell parameters were refined by the
Rietveld analysis, infers that ceramics crystallized in single-phase cubic structure with Fd-3m space group. The variation in cell parameters with
Ni substitution confirmed the partial substitution of the Co3þ by Ni3þ into the spinel CoFe2O4 structure. A blue shift in Ni doped CoFe2O4
ferrite has been observed as compared to parent CoFe2O4 from Raman scattering measurements. The dielectric constant (ε0) and loss tangent
(tan δ) have been investigated as a function of composition and frequency in the frequency range 10 Hz–1 MHz. Porous ceramics are useful for
microelectronics with lower value of dielectric constant.
(XRD), Raman spectroscopy and vibrating sample magnetometer (VSM). Rietveld – refined X-ray powder diffraction patterns at room temperature confirmed the formation of single-phase cubic (FCC) structure with Fd3m space group for all prepared samples. Slight variation in the lattice parameter of Mg doped CoFe2O4 has been observed. Raman analysis reveals the doublet like nature of A1g mode for all synthesized samples. Small shift in Raman modes and increment in the linewidth has been observed with the doping ions. The magnetic measurement explored that the saturation value (Ms) is maximum for CoFe2O4 as compared to Zn and Mg doped cobalt ferrites samples.
at Fe site
Conference Presentations
state reaction method. Structural studies through X-ray diffraction shows that all prepared ceramics
crystallized in a rhombohedrally (R3C) distorted BiFeO3 structure with compressive lattice distortion
induced by the rare earth (La3+) ion and divalent co-doping at the Bi-site for the Raman study. Scanning
electron micrograph of the compounds showed the uniform distribution of grains on the sample surface
with high density. A large ferromagnetic hysteresis loop is observed for La/Ba co-doped BiFeO3 as
compared with BiFeO3 prepared under similar conditions, with saturation magnetization of 6.85 emu/g
and remnant magnetization of 2.72 emu/g at 300K. Clear ferromagnetic ground state was observed in
Bi0.80La0.15Ba0.05FeO3 and weak ferromagnetism in BLCFO and BLSFO samples. Dielectric constant and
dielectric loss were found to decrease with increase in frequency for all the compounds. These improved
properties of La/Ba co-doped BFO demonstrate the possibility of enhancing the magnetic applicability
and makes very promising for industrial applications such as new devices in information storage.
refined X-ray diffraction patterns confirmed the formation of single-phase perovskite structure and all the peaks of
Bi2Fe4O9 perfectly indexed to the orthorhombic (space group Pbam). Raman scattering measurements identifies
12Ag+1B2g+1B3g Raman active optical phonon modes. Apart from phonon scattering, mode at 470 cm−1 is observed
which is due to magnon scattering. The P-E loop infers paraelectric nature of Bi2Fe4O9.
prepared by solid-state reaction route. Rietveld refined X-ray diffraction pattern confirmed the formation of single-phase
and both of the samples perfectly indexed in cubic spinel structure with Fd3m space group. Slight reduction in the lattice
parameter of Co0.5Ni0.5Fe2O4 has been observed as compared to CoFe2O4. From Raman scattering spectra, a shoulder like
feature has been observed in both of the compounds reveals that octahedral site is occupied by Co, Ni and Fe ions and
tetrahedral site is occupied by only Fe ion.
method. X-ray diffraction patterns accompanied by Rietveld–refined crystal structure parameters reveal the
phase transition of Bi0.8Nd0.1Ca0.1FeO3 with rhombohedral R3c symmetry to triclinic structure of Bi0.8Nd0.2FeO3 sample.
Frequency dependence of dielectric constant (e’) and dielectric loss (tand), infers enhancement of both e’ (tand) in
narrow band gap of Nd/Ca co-doped BFO as compare to wide band pristine BFO.
route to discuss doping effect on the structural, vibrational and dielectric properties. The crystal structure and cell parameters were refined by the
Rietveld analysis, infers that ceramics crystallized in single-phase cubic structure with Fd-3m space group. The variation in cell parameters with
Ni substitution confirmed the partial substitution of the Co3þ by Ni3þ into the spinel CoFe2O4 structure. A blue shift in Ni doped CoFe2O4
ferrite has been observed as compared to parent CoFe2O4 from Raman scattering measurements. The dielectric constant (ε0) and loss tangent
(tan δ) have been investigated as a function of composition and frequency in the frequency range 10 Hz–1 MHz. Porous ceramics are useful for
microelectronics with lower value of dielectric constant.
(XRD), Raman spectroscopy and vibrating sample magnetometer (VSM). Rietveld – refined X-ray powder diffraction patterns at room temperature confirmed the formation of single-phase cubic (FCC) structure with Fd3m space group for all prepared samples. Slight variation in the lattice parameter of Mg doped CoFe2O4 has been observed. Raman analysis reveals the doublet like nature of A1g mode for all synthesized samples. Small shift in Raman modes and increment in the linewidth has been observed with the doping ions. The magnetic measurement explored that the saturation value (Ms) is maximum for CoFe2O4 as compared to Zn and Mg doped cobalt ferrites samples.
at Fe site