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, microstr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, microstr
