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
The paper presents the results of studies surface microrelief, frequency-temperature characteristics of the imaginary part of the dielectric permittivity and dielectric loss of PE+TlInSe2 composite materials in 25。C ...The paper presents the results of studies surface microrelief, frequency-temperature characteristics of the imaginary part of the dielectric permittivity and dielectric loss of PE+TlInSe2 composite materials in 25。C - 150。C temperature and 25 Hz - 1 MHz frequency range before and after application of the aluminum nano-particles with a size of 50 nm. The change in the amount of semicon-ductor filler TlInSe2 and aluminum nano-particles changes the state of the surface and the frequency-temperature characteristics of composite materials PE+xvol.%TlInSe2, which allows to obtain composites with the desired dielectric permittivity and dielectric loss.展开更多
Co-SiC core-shell powders were prepared by electroless plating. Scanning electron microscopy （SEM） revealed that Co-SiC core-shell powders were of nearly sphere-like shape and were about 0.3 pan. X-ray powder diffra...Co-SiC core-shell powders were prepared by electroless plating. Scanning electron microscopy （SEM） revealed that Co-SiC core-shell powders were of nearly sphere-like shape and were about 0.3 pan. X-ray powder diffraction （XRD） patterns showed that the cobalt powder was hexagonal crystallite. The complex dielectric constant and the complex permeability of Co-SiC core-shell powders-paraffin wax composite were measured by the rectangle wavegnide method. It showed that the dielectric loss was less than 0.1 and the magnetic loss was about 0.2 in 8.2-12.4 GHz for prepared Co-SiC core-shell comoosite oowders.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
In the paper, the results of investigations of temperature and frequency dependences of dielectric permeability and dielectric loss of compositions LDPE + xvol%Bi<sub>2</sub>Te<sub>3</sub> are ...In the paper, the results of investigations of temperature and frequency dependences of dielectric permeability and dielectric loss of compositions LDPE + xvol%Bi<sub>2</sub>Te<sub>3</sub> are stated. The investigations were carried out at frequency 10 – 10<sup>5</sup> Hz and temperature 20°C - 150°C intervals, respectively. It was revealed that increase of percentage of the filler Bi<sub>2</sub>Te<sub>3</sub> in the matrix, reduces to increase of dielectric permeability and dielectric loss of composites LDPE + xvol%Bi<sub>2</sub>Te<sub>3</sub> in connection with the change reducing to Maxwell-Wagner’s volume polarization and emergence of comparative strong inner field in semiconductor clusters.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The paper presents the results of studies surface microrelief, frequency-temperature characteristics of the imaginary part of the dielectric permittivity and dielectric loss of PE+TlInSe2 composite materials in 25。C - 150。C temperature and 25 Hz - 1 MHz frequency range before and after application of the aluminum nano-particles with a size of 50 nm. The change in the amount of semicon-ductor filler TlInSe2 and aluminum nano-particles changes the state of the surface and the frequency-temperature characteristics of composite materials PE+xvol.%TlInSe2, which allows to obtain composites with the desired dielectric permittivity and dielectric loss.
基金This work was financially supported by the Science Fund for Distinguished Young Scholars of Henan Province, China (No. 0512002400)
文摘Co-SiC core-shell powders were prepared by electroless plating. Scanning electron microscopy （SEM） revealed that Co-SiC core-shell powders were of nearly sphere-like shape and were about 0.3 pan. X-ray powder diffraction （XRD） patterns showed that the cobalt powder was hexagonal crystallite. The complex dielectric constant and the complex permeability of Co-SiC core-shell powders-paraffin wax composite were measured by the rectangle wavegnide method. It showed that the dielectric loss was less than 0.1 and the magnetic loss was about 0.2 in 8.2-12.4 GHz for prepared Co-SiC core-shell comoosite oowders.
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
文摘In the paper, the results of investigations of temperature and frequency dependences of dielectric permeability and dielectric loss of compositions LDPE + xvol%Bi<sub>2</sub>Te<sub>3</sub> are stated. The investigations were carried out at frequency 10 – 10<sup>5</sup> Hz and temperature 20°C - 150°C intervals, respectively. It was revealed that increase of percentage of the filler Bi<sub>2</sub>Te<sub>3</sub> in the matrix, reduces to increase of dielectric permeability and dielectric loss of composites LDPE + xvol%Bi<sub>2</sub>Te<sub>3</sub> in connection with the change reducing to Maxwell-Wagner’s volume polarization and emergence of comparative strong inner field in semiconductor clusters.
