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
A series of Cr<sup>3+</sup>-substituted Mn-Ni–Zn ferrites;Mn<sub>0.5</sub>Ni<sub>0.1</sub>Zn<sub>0.4</sub>Fe<sub>2-x</sub>Cr<sub>x</sub>O<sub...A series of Cr<sup>3+</sup>-substituted Mn-Ni–Zn ferrites;Mn<sub>0.5</sub>Ni<sub>0.1</sub>Zn<sub>0.4</sub>Fe<sub>2-x</sub>Cr<sub>x</sub>O<sub>4</sub> (<em>x</em> = 0.0 - 0.4 in a step of 0.1) were prepared by traditional solid-state reaction route. The structural, magnetic, dielectric properties and impedance spectroscopy of these compositions were studied. Phase identification and lattice constant (a<sub>0</sub>) determination were carried out by X-ray diffraction (XRD). The XRD patterns established the fabrication of a single-phase spinel structure. The FESEM micrographs exposed that the average grain size (<img src="Edit_da92e8c9-165d-4d71-aaf5-717db2aa65e1.png" alt="" />) increased slightly with chromium (Cr) substitution and then decreased for a higher concentration of chromium in the composition. The real part of initial permeability (<img src="Edit_1d356971-e483-44dc-875c-698f938e7d9f.png" alt="" />) diminished owing to the enhanced porosity of the compositions with the increase of Cr<sup>3+</sup> content in the composition. The highest relative quality factor (RQF) was attained for the samples with x = 0.1. The magnetic hysteresis was investigated to know the effect of Cr<sup>3+</sup> substitution in the composition of the magnetic properties. The decrease of saturation magnetization (<em>M<sub>s</sub></em>) with an enhancement in Cr<sup>3+</sup> might be triggered by switching of Fe<sup>3+</sup> ions from octahedral to tetrahedral site. The samples with x = 0.1 exhibited the highest anisotropy constant (<em>K</em>). Curie temperatures of the investigated samples were significantly modified to lower temperatures with the Cr<sup>3+</sup> content. The frequency characteristics of dielectric properties and impedance spectroscopy had been investigated. The highest dielectric constant (<em><span style="white-space:nowrap;">ε</span>'</em>) and resistivity were observed for x = 0.1 and x = 0.2 samples. The complex impedance spectra analysis reveals in-depth information about the conduction mechanism, microstructure, and orientation of the grains in the samples.展开更多
Y-type hexagonal ferrites with the nominal chemical composition Ba2Ni2-xZnxFe12O22 (0.0 ≤ x ≤ 0.6 with a step of 0.1) have been synthesized by the conventional solid state reaction method and sintered in the tempera...Y-type hexagonal ferrites with the nominal chemical composition Ba2Ni2-xZnxFe12O22 (0.0 ≤ x ≤ 0.6 with a step of 0.1) have been synthesized by the conventional solid state reaction method and sintered in the temperature range 1150℃-1250℃ to study their structural and magnetic properties. The aim of the present work is to increase the magnetic properties of Y-type hexaferrites by Zn substitution. X-ray diffraction analysis confirms the formation of the hexagonal phase. The effect of chemical composition on the lattice parameter, density and porosity is studied. The lattice parameter increases with Zn substitution. The density increases with Zn substitution up to a certain level and after that density decreases. The ac magnetic properties of the hexaferrites sintered at temperature 1200℃ are characterized within the frequency range 100 kHz -120 MHz. The real part (μi') of the complex initial permeability for different compositions indicates that μi' decreases with increase in frequency. The permeability increases with the increase in Zn content, reaches a maximum value and then decreases with further increase in Zn content. Magnetization has been measured using the Superconducting Quantum Interference Device (SQUID) magnetometer. The saturation magnetization is observed to be maximum at x = 0.1 and then decreases with Zn content for x > 0.1. From the M-H curve it is clear that at room temperature the polycrystalline Ba2Ni2-xZnxFe12O22 compositions are in ferrimagnetic state.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A series of Cr<sup>3+</sup>-substituted Mn-Ni–Zn ferrites;Mn<sub>0.5</sub>Ni<sub>0.1</sub>Zn<sub>0.4</sub>Fe<sub>2-x</sub>Cr<sub>x</sub>O<sub>4</sub> (<em>x</em> = 0.0 - 0.4 in a step of 0.1) were prepared by traditional solid-state reaction route. The structural, magnetic, dielectric properties and impedance spectroscopy of these compositions were studied. Phase identification and lattice constant (a<sub>0</sub>) determination were carried out by X-ray diffraction (XRD). The XRD patterns established the fabrication of a single-phase spinel structure. The FESEM micrographs exposed that the average grain size (<img src="Edit_da92e8c9-165d-4d71-aaf5-717db2aa65e1.png" alt="" />) increased slightly with chromium (Cr) substitution and then decreased for a higher concentration of chromium in the composition. The real part of initial permeability (<img src="Edit_1d356971-e483-44dc-875c-698f938e7d9f.png" alt="" />) diminished owing to the enhanced porosity of the compositions with the increase of Cr<sup>3+</sup> content in the composition. The highest relative quality factor (RQF) was attained for the samples with x = 0.1. The magnetic hysteresis was investigated to know the effect of Cr<sup>3+</sup> substitution in the composition of the magnetic properties. The decrease of saturation magnetization (<em>M<sub>s</sub></em>) with an enhancement in Cr<sup>3+</sup> might be triggered by switching of Fe<sup>3+</sup> ions from octahedral to tetrahedral site. The samples with x = 0.1 exhibited the highest anisotropy constant (<em>K</em>). Curie temperatures of the investigated samples were significantly modified to lower temperatures with the Cr<sup>3+</sup> content. The frequency characteristics of dielectric properties and impedance spectroscopy had been investigated. The highest dielectric constant (<em><span style="white-space:nowrap;">ε</span>'</em>) and resistivity were observed for x = 0.1 and x = 0.2 samples. The complex impedance spectra analysis reveals in-depth information about the conduction mechanism, microstructure, and orientation of the grains in the samples.
文摘Y-type hexagonal ferrites with the nominal chemical composition Ba2Ni2-xZnxFe12O22 (0.0 ≤ x ≤ 0.6 with a step of 0.1) have been synthesized by the conventional solid state reaction method and sintered in the temperature range 1150℃-1250℃ to study their structural and magnetic properties. The aim of the present work is to increase the magnetic properties of Y-type hexaferrites by Zn substitution. X-ray diffraction analysis confirms the formation of the hexagonal phase. The effect of chemical composition on the lattice parameter, density and porosity is studied. The lattice parameter increases with Zn substitution. The density increases with Zn substitution up to a certain level and after that density decreases. The ac magnetic properties of the hexaferrites sintered at temperature 1200℃ are characterized within the frequency range 100 kHz -120 MHz. The real part (μi') of the complex initial permeability for different compositions indicates that μi' decreases with increase in frequency. The permeability increases with the increase in Zn content, reaches a maximum value and then decreases with further increase in Zn content. Magnetization has been measured using the Superconducting Quantum Interference Device (SQUID) magnetometer. The saturation magnetization is observed to be maximum at x = 0.1 and then decreases with Zn content for x > 0.1. From the M-H curve it is clear that at room temperature the polycrystalline Ba2Ni2-xZnxFe12O22 compositions are in ferrimagnetic state.
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.
