The novel polycrystalline Bi<sub>0.85</sub>Gd<sub>0.15</sub>Cu<sub>x</sub>Fe<sub>1-x</sub>O<sub>3</sub> (x = 0, 0.025, 0.05, 0.075, 0.10) multiferroics are s...The novel polycrystalline Bi<sub>0.85</sub>Gd<sub>0.15</sub>Cu<sub>x</sub>Fe<sub>1-x</sub>O<sub>3</sub> (x = 0, 0.025, 0.05, 0.075, 0.10) multiferroics are synthesized by the usual solid-state reaction route. The synthesis of the desired phase has been verified by the X-ray Diffraction (XRD) patterns. With major structural phases, few traces of secondary phases of Bi<sub>2</sub>Fe<sub>4</sub>O<sub>9</sub> and Bi<sub>25</sub>FeO<sub>40</sub> appear for all the compositions. A discontinuous series of structural changes with varying compositions are observed for the doped samples. The bulk density (ρ<sub>B</sub>) increases with Cu content reaches the highest at x = 0.05 and then declines. The complex initial permeability and dielectric characterizations are performed by Wayne Kerr Impedance Analyzer. The x = 0.05 samples having maximum density exhibit the highest permeability (μ<sub>i</sub>’) implying a close relation between μ<sub>i</sub>’ and the density. The reduction of μ<sub>i</sub>’ at higher Cu concentration is due to the low density of the samples associated with the increased intragranular pores. The dielectric constant (ε’) is measured against frequency in the range 1 kHz - 10 MHz. It is perceived that ε’ falls with the rise in frequency up to 100 kHz. This dielectric dispersion is observed at a lower frequency as a result of interfacial polarization outlined by Maxwell-Wagner. The maximum ε’ is obtained for x = 0.025 composition. In the low-frequency range, the AC conductivity σ<sub>AC</sub> is practically independent of frequency and resembles the DC conductivity (σ<sub>DC</sub>). In the vicinity of high frequency recognized as the hopping region, σ<sub>AC</sub> rises since the conductive grains are more active at high frequencies. The co-doping with Gd and Cu in BiFeO<sub>3</sub> ceramics enhances the magnetic and dielectric properties of the ceramics and hence can be utilized for fabricating multifunctional devices.展开更多
Mn0.50-xZn0.50CuxFe2O4 (where x = 0.0 - 0.3) ferrites have been synthesized by auto combustion method. X-ray diffraction patterns reveal that all compositions are of single phase cubic spinel structure. The lattice pa...Mn0.50-xZn0.50CuxFe2O4 (where x = 0.0 - 0.3) ferrites have been synthesized by auto combustion method. X-ray diffraction patterns reveal that all compositions are of single phase cubic spinel structure. The lattice parameter decreases with the increase in Cu2+ content obeying the Vegard’s law. The bulk density, average grain size, initial permeability, Néel temperature and saturation magnetic induction of Mn0.50-xZn0.50CuxFe2O4 increased with increasing Cu2+content. It is observed that both density and initial permeability increase with increasing sintering temperature. The maximum initial permeability is found to be 1061 which is almost four times greater than that of the parent composition. The resonance frequency of all the samples shifts towards the lower frequency as the permeability increases with Cu2+ content. It is observed from B-H loops of Mn0.50-xZn0.50CuxFe2O4 that coercivity decreases and retentivity increases with Cu2+ content. Possible explanations for the observed magnetic properties with various Cu2+ contents are discussed.展开更多
Ti4+ doped Ni0.4Cu0.2Zn0.4Fe2-xTixO4 (x = 0.0, 0.02, 0.05, 0.07, 0.10) chemical compositions are prepared by conventional solid state reaction technique. The ferrite phase formation has been confirmed from the pattern...Ti4+ doped Ni0.4Cu0.2Zn0.4Fe2-xTixO4 (x = 0.0, 0.02, 0.05, 0.07, 0.10) chemical compositions are prepared by conventional solid state reaction technique. The ferrite phase formation has been confirmed from the pattern of XRD. The theoretical density (ρth), bulk density (ρB), and porosity are calculated from the XRD data and using approximate formulas. Value of ρth is found to be greater than the value of ρB indicating the formation of pores inside the bulk specimens. The micro-structural investigation has been done using Field Emission Scanning Electron Microscope and it is found that the average grain size reduces with the increase of Ti content. Saturation magnetization (Ms) also reduces with the increase of Ti content, contrarily remanent magnetization (Mr) and coercivity (Hc) increases with the concentration of Ti in the composition due to the pinning effect. The real part of the initial permeability is found to be maximum for the x = 0.02 sample which could be due to the homogeneity and high density of the sample. For increasing frequency, the dielectric constant and dielectric loss are observed to decrease.展开更多
文摘The novel polycrystalline Bi<sub>0.85</sub>Gd<sub>0.15</sub>Cu<sub>x</sub>Fe<sub>1-x</sub>O<sub>3</sub> (x = 0, 0.025, 0.05, 0.075, 0.10) multiferroics are synthesized by the usual solid-state reaction route. The synthesis of the desired phase has been verified by the X-ray Diffraction (XRD) patterns. With major structural phases, few traces of secondary phases of Bi<sub>2</sub>Fe<sub>4</sub>O<sub>9</sub> and Bi<sub>25</sub>FeO<sub>40</sub> appear for all the compositions. A discontinuous series of structural changes with varying compositions are observed for the doped samples. The bulk density (ρ<sub>B</sub>) increases with Cu content reaches the highest at x = 0.05 and then declines. The complex initial permeability and dielectric characterizations are performed by Wayne Kerr Impedance Analyzer. The x = 0.05 samples having maximum density exhibit the highest permeability (μ<sub>i</sub>’) implying a close relation between μ<sub>i</sub>’ and the density. The reduction of μ<sub>i</sub>’ at higher Cu concentration is due to the low density of the samples associated with the increased intragranular pores. The dielectric constant (ε’) is measured against frequency in the range 1 kHz - 10 MHz. It is perceived that ε’ falls with the rise in frequency up to 100 kHz. This dielectric dispersion is observed at a lower frequency as a result of interfacial polarization outlined by Maxwell-Wagner. The maximum ε’ is obtained for x = 0.025 composition. In the low-frequency range, the AC conductivity σ<sub>AC</sub> is practically independent of frequency and resembles the DC conductivity (σ<sub>DC</sub>). In the vicinity of high frequency recognized as the hopping region, σ<sub>AC</sub> rises since the conductive grains are more active at high frequencies. The co-doping with Gd and Cu in BiFeO<sub>3</sub> ceramics enhances the magnetic and dielectric properties of the ceramics and hence can be utilized for fabricating multifunctional devices.
文摘Mn0.50-xZn0.50CuxFe2O4 (where x = 0.0 - 0.3) ferrites have been synthesized by auto combustion method. X-ray diffraction patterns reveal that all compositions are of single phase cubic spinel structure. The lattice parameter decreases with the increase in Cu2+ content obeying the Vegard’s law. The bulk density, average grain size, initial permeability, Néel temperature and saturation magnetic induction of Mn0.50-xZn0.50CuxFe2O4 increased with increasing Cu2+content. It is observed that both density and initial permeability increase with increasing sintering temperature. The maximum initial permeability is found to be 1061 which is almost four times greater than that of the parent composition. The resonance frequency of all the samples shifts towards the lower frequency as the permeability increases with Cu2+ content. It is observed from B-H loops of Mn0.50-xZn0.50CuxFe2O4 that coercivity decreases and retentivity increases with Cu2+ content. Possible explanations for the observed magnetic properties with various Cu2+ contents are discussed.
文摘Ti4+ doped Ni0.4Cu0.2Zn0.4Fe2-xTixO4 (x = 0.0, 0.02, 0.05, 0.07, 0.10) chemical compositions are prepared by conventional solid state reaction technique. The ferrite phase formation has been confirmed from the pattern of XRD. The theoretical density (ρth), bulk density (ρB), and porosity are calculated from the XRD data and using approximate formulas. Value of ρth is found to be greater than the value of ρB indicating the formation of pores inside the bulk specimens. The micro-structural investigation has been done using Field Emission Scanning Electron Microscope and it is found that the average grain size reduces with the increase of Ti content. Saturation magnetization (Ms) also reduces with the increase of Ti content, contrarily remanent magnetization (Mr) and coercivity (Hc) increases with the concentration of Ti in the composition due to the pinning effect. The real part of the initial permeability is found to be maximum for the x = 0.02 sample which could be due to the homogeneity and high density of the sample. For increasing frequency, the dielectric constant and dielectric loss are observed to decrease.
