To explore the mechanism of carbonyl iron flake composites for microwave complex permeability, this paper investigates the feature of the flakes. The shape anisotropy was certified by the results of the magnetization ...To explore the mechanism of carbonyl iron flake composites for microwave complex permeability, this paper investigates the feature of the flakes. The shape anisotropy was certified by the results of the magnetization hysteresis loops and the Mossbauer spectra. Furthermore, the shape anisotropy was used to explain the origin of composite microwave performance, and the calculated results agree with the experiment. It is believed that the shape anisotropy dominates microwave complex permeability, and the natural resonance plays main role in flake.展开更多
CIP （complex initial permeability） spectra of PF （polycrystalline ferrite） are studied both as intrinsic and extrinsic properties. In the former case, main steps of modeling, based on effects coming from polycryst...CIP （complex initial permeability） spectra of PF （polycrystalline ferrite） are studied both as intrinsic and extrinsic properties. In the former case, main steps of modeling, based on effects coming from polycrystal grain sizes distribution and defects, are described. The obtained relations work well in practice for PF with more or less normal MS （microstructure） and no size effects. Besides, fundamental connection between parameters of CIP and MS is found. Another case--PF with possible size effects （MnZn-ferrites） are studied experimentally for different sizes of cores, unveiling the dependence of phenomena on： dimensions of cross-section, number of turns, width of nonmagnetic gap.展开更多
Soft magnetic composites made from metallic magnetic particles with an easy magnetization plane(referred to as easy-plane metallic soft magnetic composites(SMC))are considered ideal materials for the next generation o...Soft magnetic composites made from metallic magnetic particles with an easy magnetization plane(referred to as easy-plane metallic soft magnetic composites(SMC))are considered ideal materials for the next generation of power electronic devices.This advantage is attributed to their ability to maintain high permeability at elevated frequencies.Despite these advantages,a definitive mathematical model that connects the high-frequency magnetic properties(e.g.,effective permeability)of easy-plane metallic SMCs to the intrinsic properties of the particles is still lacking.In this work,a theoretical calculation model for the effective permeability of easy-plane metallic SMCs was formulated.This model was derived from a skin effect-corrected Landau-Lifshitz-Gilbert(LLG)equation and integrated with effective medium theory incorporating inter-particle interaction.To validate the model,we prepared samples of easy-plane Y_(2)Co_(17)particle/PU SMCs with varying particle sizes and volume fractions.The experimental results showed a strong agreement with the calculated values.This research offers critical theoretical backing for the design and optimization of soft magnetic materials intended for high-frequency applications.展开更多
Ni0.4Zn0.6Fe2-xNdxO4（x = 0-0.07） ferrites doped with different amounts of Nd2O3 were prepared using standard ceramic technique. The samples were uniaxially pressed and sintered at 1250℃ for 4 h in air. The phase st...Ni0.4Zn0.6Fe2-xNdxO4（x = 0-0.07） ferrites doped with different amounts of Nd2O3 were prepared using standard ceramic technique. The samples were uniaxially pressed and sintered at 1250℃ for 4 h in air. The phase structure and microstructure of the samples were investigated using X-ray diffraction and scanning electron microscope, respectively. The complex permeability was measured using the impedance analyzer in the range of 1-100 MHz. The results indicate that with increasing Nd^3＋ content, the relative density and lattice parameter a of the sintered samples increase, whereas the real part of permeability （μ′） and the magnetic loss tangent （tan δ） decrease. The substitution of Nd^3＋ for Fe^3＋ forms a secondary phase on the grain boundary of the matrix, which strongly restrains the grain growth of the matrix.展开更多
NiZn ferrite thin fihns were performed on glass substrates of 85 ℃ by spin spray plating method. X-ray diffraction patterns of the films show that the samples have a cubic spinel structure with no extra lines corresp...NiZn ferrite thin fihns were performed on glass substrates of 85 ℃ by spin spray plating method. X-ray diffraction patterns of the films show that the samples have a cubic spinel structure with no extra lines corresponding to any other phases between 75 ℃ and 85 ℃. As the pH value of oxidizing solution increases to 8.3, the saturation magnetization increases to 3.13 × 10^5 A/m and resistivity to 127 m Ω ·cm. Film deposited at pH 7.8 has a smooth surface and definite columnar structure. The large wavy flakes were observed at pH 8.3. The high real part of complex permeability μ′ up to 36.1 and the imaginary part μ″ up to 53.2 were observed at 0.5 GHz by short microstrip line perturbation method. The μ″ of thin film has values higher than 20 at the frequencies between 0.5 GHz and 2 GHz, the film is a promising anti-noise material for high frequency applications,展开更多
FeSiAl alloys ribbons synthesized by melt-quench were annealed in vacuum at 873 K for 60 rain. The flaky powders were prepared by milling the annealed ribbons for 70 h. After milling, the powders were heat treated at ...FeSiAl alloys ribbons synthesized by melt-quench were annealed in vacuum at 873 K for 60 rain. The flaky powders were prepared by milling the annealed ribbons for 70 h. After milling, the powders were heat treated at 573 K for 90 rain. The ordering degree of the powders lattice structure was analyzed by X-ray diffraction （XRD）. The measurement of specific saturation magnetization was carried out by vibrating samples magnetometer （VSM）. Complex permittivity and complex permeability in the frequency band of 0.5-18 GHz were measured with the vector network analyzer. The ordering degree of the superlattice structure increased from 0.2＇7 to 0.49. Complex permittivity and complex permeability decreased with increasing Si content. After ordering, the specific saturation magnetization decreased from 134.2 to 85.0 A.m2.kg-1. For use in anti-EMI material, the total contents of Si and Al in FeSiAl alloys should be controlled at a low level.展开更多
The main focus of the research was to correlate the microstructure with dielectric and magnetic properties of Bi1-xBaxFeO3 samples. Bi1-xBaxFeO3 samples（x = 0.1, 0.2 and 0.3） were synthesized by the conventional sol...The main focus of the research was to correlate the microstructure with dielectric and magnetic properties of Bi1-xBaxFeO3 samples. Bi1-xBaxFeO3 samples（x = 0.1, 0.2 and 0.3） were synthesized by the conventional solid-state reaction method using nano-powders of Bi2O3, Fe2O3, and BaCO3. Thereafter, field emission scanning electron microscope and X-ray diffraction（XRD） techniques were used to examine the structure and phase of the samples. Phase analysis by XRD indicated that the single-phase perovskite structure was formed with possible increment in lattice parameter with increasing Ba doping. Complex permeability（u＇iand u＇＇i） measured using impedance analyzer confirmed the increase in magnetic property with increasing Ba doping. Finally, dielectric constant（k） was analyzed as a function of temperature at different frequencies. Dielectric constant as high as 2900 was attained in this research for Bi0.8Ba0.2FeO3 sample due to reduction in leakage current at this composition.展开更多
Spinel NiZn ferrite thin films were prepared on glass substrates by spray plating method. Adding cetyltrimethylammoniumchloride （CTAC）, adsorptive energy of substrate surface increased, and smooth surface and unifor...Spinel NiZn ferrite thin films were prepared on glass substrates by spray plating method. Adding cetyltrimethylammoniumchloride （CTAC）, adsorptive energy of substrate surface increased, and smooth surface and uniform columnar film structures were observed. The optimum reaction temperature up to 85℃ and pH up to 7.5 were obtained. As the solution pH value increases from 6.5 to 7.5, the film saturation magnetization increases to 36.1 and the imaginary part μ″ up to 53.2 for NiZn ferrite film at 500 MHz were achieved, and higher magnetic resonance at 508 MHz was observed. As the ferrite plate thickness is 50 μm, the attenuating characteristics for reflection loss ≤-0.8 dB can be obtained in the wide frequency ranging from 0.5 to 2.7 GHz. Theμ″ of thin film has values higher than 20 at the frequencies between 0.5 and 2 GHz, and the thin film can be applied as shielding material in GHz range.展开更多
The reflection properties of planar anisotropy FesoNiso powder/paraffin composites have been studied in the microwave frequency range. The permeability of Fe50Ni50 powder/paraffin composites is greatly enhanced by int...The reflection properties of planar anisotropy FesoNiso powder/paraffin composites have been studied in the microwave frequency range. The permeability of Fe50Ni50 powder/paraffin composites is greatly enhanced by introducing the planar anisotropy, and can be further enhanced by using a rotational orientation method. The complex permeability can be considered as the superposition of two types of magnetic resonance. The resonance peak at high frequency is attributed to the natural resonance, while the peak at low frequency is attributed to the domain-wall resonance. The simulated results of the microwave reflectivity show that the matching thickness, peak frequency, permeability, and permittivity are closely related to the quarter wavelength matching condition. The Fe50Ni50 powder/paraffin composites can be attractive candidates for thinner microwave absorbers in the L-band （1-2 GHz）.展开更多
The reflection properties of planar anisotropy Fe50Ni50 powder/paraffin composites have been studied in the microwave frequency range.The permeability of Fe50Ni50 powder/paraffin composites is greatly enhanced by intr...The reflection properties of planar anisotropy Fe50Ni50 powder/paraffin composites have been studied in the microwave frequency range.The permeability of Fe50Ni50 powder/paraffin composites is greatly enhanced by introducing the planar anisotropy,and can be further enhanced by using a rotational orientation method.The complex permeability can be considered as the superposition of two types of magnetic resonance.The resonance peak at high frequency is attributed to the natural resonance,while the peak at low frequency is attributed to the domain-wall resonance.The simulated results of the microwave reflectivity show that the matching thickness,peak frequency,permeability,and permittivity are closely related to the quarter wavelength matching condition.The Fe50Ni50 powder/paraffin composites can be attractive candidates for thinner microwave absorbers in the L-band(1-2 GHz).展开更多
Polycrystalline xBa<sub>0.95</sub>Sr<sub>0.05</sub>TiO<sub>3</sub>-(1 - x)BiFe<sub>0.90</sub>Gd<sub>0.10</sub>O<sub>3</sub> ceramics were prepare...Polycrystalline xBa<sub>0.95</sub>Sr<sub>0.05</sub>TiO<sub>3</sub>-(1 - x)BiFe<sub>0.90</sub>Gd<sub>0.10</sub>O<sub>3</sub> ceramics were prepared by standard solid state reaction technique using the solid solution of BaCO<sub>3</sub>, SrCO<sub>3</sub>, TiO<sub>2</sub>, Bi<sub>2</sub>O<sub>3</sub>, Fe<sub>2</sub>O<sub>3</sub> and Gd<sub>2</sub>O<sub>3</sub>. The compound is a BiFeO<sub>3</sub> based multiferroic material which contains both magnetic and electric properties. The synthesized ceramics noticed better properties than xBaTiO<sub>3</sub>-(1 - x)BiFeO<sub>3</sub> because of adding rare earth element Gd which have higher magnetic moment than Fe. The prepared samples were sintered at 900<span style="font-size:12px;white-space:nowrap;"><span style="font-size:12px;white-space:nowrap;">˚</span></span>C, 950<span style="font-size:12px;white-space:nowrap;"><span style="font-size:12px;white-space:nowrap;">˚</span></span>C and 1000<span style="font-size:12px;white-space:nowrap;"><span style="font-size:12px;white-space:nowrap;">˚</span></span>C for 1 h. The effect of sintering temperature on density of the compound, complex initial permeability, dielectric properties and complex impedance analysis was reported in this article. Density of the ceramics was found to be enhanced with the rise in sintering temperature which implied porosity of the compound decreased when sintering temperature was increased. Enhanced complex initial permeability was noticed for the samples up to 950<span style="font-size:12px;white-space:nowrap;"><span style="font-size:12px;white-space:nowrap;">˚</span></span>C and this might be attributed to reducing the motion of domain wall when the ceramics were sintered above 950<span style="font-size:12px;white-space:nowrap;"><span style="font-size:12px;white-space:nowrap;">˚</span></span>C. Value of dielectric constant increased whereas dielectric loss decreased and these modifications might be expected because of changing density and grain size due to the variation of sintering temperature. Grain resistance (resistance due to grains) was determined from complex impedance analysis and it reduced with the rise in sintering temperature. The studied multiferroic material exhibited weak ferromagnetism but is an alternative product of environmental hazard lead (Pb) based multiferroic material and it is expected to be environment friendly.展开更多
The polycrystalline Li<em><sub>x</sub></em>Ni<sub>0.2</sub>Zn<sub>0.8-2</sub><em><sub>x</sub></em>Fe<em><sub>x</sub></em>...The polycrystalline Li<em><sub>x</sub></em>Ni<sub>0.2</sub>Zn<sub>0.8-2</sub><em><sub>x</sub></em>Fe<em><sub>x</sub></em><sub>+2</sub>O<sub>4</sub> and Li<em><sub>x</sub></em>Ni<sub>0.1</sub>Cu<sub>0.1</sub>Zn<sub>0.8-2</sub><em><sub>x</sub></em>Fe<em><sub>x</sub></em><sub>+2</sub>O<sub>4</sub> (<em>x</em> = 0.0, 0.1, 0.2, and 0.3) ferrites were synthesized by the standard solid-state reaction method. The compound was sintered at 1150<span style="font-size:12px;white-space:nowrap;">˚</span>C for 5 hours. The effect of Cu substitution and its impact on the crystal structure, microstructure, complex initial permeability and magnetization of the Ni-Zn ferrites were studied. The effect of Li<sup>+</sup> incorporation on the properties mentioned above was also investigated. X-ray diffraction patterns of the samples indicated a single cubic spinel structure for both the compound. No effect of Cu addition on crystal structure was observed. The density of the ferrites was found to be enhanced because of adding Li whereas the porosity of the samples decreased with the content of Li ions. The average value of grain size increased with the addition of Li content. The samples having Cu ions formed bigger size grains. Frequency-dependent complex initial permeability, loss tangent, and relative quality factor were studied at room temperature using an Impedance analyzer in the range of 100 Hz - 120 MHz regions. In the low-frequency region, the prepared samples exhibited a high value of permeability and after a certain frequency, the permeability falls. The value of permeability enhanced with the increase in Li whereas loss tangent was found to be reduced. The relative quality factor graphs described that the compound has excellent frequency stability up to a certain frequency which is suitable to be used in inductors, resistors, capacitors, etc. Initial permeability for Li<em><sub>x</sub></em>Ni<sub>0.1</sub>Cu<sub>0.1</sub>Zn<sub>0.8-2</sub><em><sub>x</sub></em>Fe<em><sub>x</sub></em><sub>+2</sub>O<sub>4</sub> ferrites was found high than Li<em><sub>x</sub></em>Ni<sub>0.2</sub>Zn<sub>0.8-2</sub><em><sub>x</sub></em>Fe<em><sub>x</sub></em><sub>+2</sub>O<sub>4</sub> which might be attributed to having bigger size grains of Cu containing samples because of easy movement of domain wall in bigger size grains. The values of saturation magnetization (<em>M</em><sub>s</sub>) were calculated for both compounds from M-H hysteresis loops and it enhanced with the increase in Li content which might be related to the modification of predominant exchange interactions between the cations. The Cu-containing compound exhibited higher values of saturation magnetization. The cation distribution reflects this increment because ferromagnetic Ni<sup>2+</sup> and paramagnetic Cu<sup>2+</sup> ions occupied in the B-sites and the diamagnetic Zn and paramagnetic Li occupied in the A-sites;therefore, net magnetic moments increased gradually. The studied materials might be used as an alternative to Pb-based compounds and would be environment friendly.展开更多
Soft magnetic composites(SMCs)play an indispensable role in electromagnetic conversion,transmission,and storage.However,achieving high-frequency,low-loss soft magnetic materials compatible with third-generation wide b...Soft magnetic composites(SMCs)play an indispensable role in electromagnetic conversion,transmission,and storage.However,achieving high-frequency,low-loss soft magnetic materials compatible with third-generation wide bandgap semiconductor devices remains a significant challenge.In this study,we report a novel strategy to fabricate Fe-based amorphous SMCs through a precisely controlled phosphating process.As the phosphoric acid content increases,the thickness of the insulating layer increases,resulting in higher resistivity.At the same time,the contribution of spin rotation to magnetization increases gradually and dominates throughout the magnetization.Compared with the untreated SMCs,the core loss(P_(cv))of the SMCs treated with 1.0 wt.%phosphoric acid at 0.1 T/1 MHz was reduced by 11.6%,primarily due to the reduction of excess losses resulting from the different magnetization mechanisms.The optimized SMCs demonstrate outstanding overall magnetic performance,including ultra-low P_(cv)of 14.35 W/cm^(3)at 0.1 T/1 MHz,excellent DC-bias stability(69.4%at 100 Oe),relatively high saturation magnetic flux density(B_(s)=0.84 T),and ultra-stable permeability(μ_(e)=32.7)up to 20 MHz.These findings offer a promising pathway for designing high-performance SMCs tailored for high-frequency and high-power electronic applications.展开更多
To address the lack of voltage ratio standards for accuracy testing of low-frequency voltage transformers,it is necessary to develop a 3 kV low-frequency induction voltage divider.Firstly,based on the analysis of the ...To address the lack of voltage ratio standards for accuracy testing of low-frequency voltage transformers,it is necessary to develop a 3 kV low-frequency induction voltage divider.Firstly,based on the analysis of the error sources of the induction voltage divider,a method was proposed to calculate the excitation impedance of the induction voltage divider using complex magnetic permeability.A measurement circuit based on the lock-in principle was set up to measure the complex magnetic permeability of grained-oriented silicon steel 30P100 and permalloy 1J85 at different frequencies.Secondly,a 3 kV low-frequency induction voltage divider with a two-stage excitation and a series-wound ra-tio winding in 10 sections was designed.The errors of the two stages of the instrument transformers were calculated at 20 and 50 Hz,respectively.Finally,the divider's errors were calibrated at 20 and 50 Hz using the reference potential method.The results showed that,compared to 50 Hz,the excitation impedance of the two stages decreased and the errors increased at 20 Hz,with the overall error of the induction voltage divider being better at 50 Hz than at 20 Hz.Experimental measurements indicated that at 20 Hz,the ratio error and phase error of the 3 kV two-stage excitation induction voltage divider were better than 110-5,whereas at 50 Hz,the errors were better than 110-6.This study provides support for the accuracy testing of voltage transformers used in low-frequency flexible AC transmission projects.展开更多
Magnetic,dielectric and DC conductive properties of Ni_(0.95-x)Zn_(x)Co_(0.05)Fe_(1.90)Mn_(0.02)O_(4)(with x=0-0.20 at an interval of 0.05)ferrite ceramics were studied,in order to develop magneto-dielectric materials...Magnetic,dielectric and DC conductive properties of Ni_(0.95-x)Zn_(x)Co_(0.05)Fe_(1.90)Mn_(0.02)O_(4)(with x=0-0.20 at an interval of 0.05)ferrite ceramics were studied,in order to develop magneto-dielectric materials with almost equal values of relative permeability and permittivity,for the miniaturization of HF(3-30 MHz)and VHF(30-90MHz and 100-300 MHz)antennas.The ferrite ceramics were prepared by using the conventional two-step sintering process.The real part of relative permeability is increased almost linearly with increasing concentration of Zn,while that of relative permittivity keeps nearly unchanged.It is found that promising magneto-dielectric materials,with close values of real permeability and permittivity over 30-90 MHz(VHF),can be obtained for the samples at Zn concentrations between x=0.05 and x=0.10.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant Nos 90505007 and 10774061)
文摘To explore the mechanism of carbonyl iron flake composites for microwave complex permeability, this paper investigates the feature of the flakes. The shape anisotropy was certified by the results of the magnetization hysteresis loops and the Mossbauer spectra. Furthermore, the shape anisotropy was used to explain the origin of composite microwave performance, and the calculated results agree with the experiment. It is believed that the shape anisotropy dominates microwave complex permeability, and the natural resonance plays main role in flake.
文摘CIP （complex initial permeability） spectra of PF （polycrystalline ferrite） are studied both as intrinsic and extrinsic properties. In the former case, main steps of modeling, based on effects coming from polycrystal grain sizes distribution and defects, are described. The obtained relations work well in practice for PF with more or less normal MS （microstructure） and no size effects. Besides, fundamental connection between parameters of CIP and MS is found. Another case--PF with possible size effects （MnZn-ferrites） are studied experimentally for different sizes of cores, unveiling the dependence of phenomena on： dimensions of cross-section, number of turns, width of nonmagnetic gap.
基金supported by the National Key R&D Program of China(Grant No.2021YFB3501300)the 9th Research Institute of China Electronics Technology Group Corporation’s open projects(Grant No.2024SK-002-01)the Science and Technology Project of Gansu Province(Grant No.22YF7GA001).
文摘Soft magnetic composites made from metallic magnetic particles with an easy magnetization plane(referred to as easy-plane metallic soft magnetic composites(SMC))are considered ideal materials for the next generation of power electronic devices.This advantage is attributed to their ability to maintain high permeability at elevated frequencies.Despite these advantages,a definitive mathematical model that connects the high-frequency magnetic properties(e.g.,effective permeability)of easy-plane metallic SMCs to the intrinsic properties of the particles is still lacking.In this work,a theoretical calculation model for the effective permeability of easy-plane metallic SMCs was formulated.This model was derived from a skin effect-corrected Landau-Lifshitz-Gilbert(LLG)equation and integrated with effective medium theory incorporating inter-particle interaction.To validate the model,we prepared samples of easy-plane Y_(2)Co_(17)particle/PU SMCs with varying particle sizes and volume fractions.The experimental results showed a strong agreement with the calculated values.This research offers critical theoretical backing for the design and optimization of soft magnetic materials intended for high-frequency applications.
文摘Ni0.4Zn0.6Fe2-xNdxO4（x = 0-0.07） ferrites doped with different amounts of Nd2O3 were prepared using standard ceramic technique. The samples were uniaxially pressed and sintered at 1250℃ for 4 h in air. The phase structure and microstructure of the samples were investigated using X-ray diffraction and scanning electron microscope, respectively. The complex permeability was measured using the impedance analyzer in the range of 1-100 MHz. The results indicate that with increasing Nd^3＋ content, the relative density and lattice parameter a of the sintered samples increase, whereas the real part of permeability （μ′） and the magnetic loss tangent （tan δ） decrease. The substitution of Nd^3＋ for Fe^3＋ forms a secondary phase on the grain boundary of the matrix, which strongly restrains the grain growth of the matrix.
基金the Advanced Research Project of the General Armament De-partment of China
文摘NiZn ferrite thin fihns were performed on glass substrates of 85 ℃ by spin spray plating method. X-ray diffraction patterns of the films show that the samples have a cubic spinel structure with no extra lines corresponding to any other phases between 75 ℃ and 85 ℃. As the pH value of oxidizing solution increases to 8.3, the saturation magnetization increases to 3.13 × 10^5 A/m and resistivity to 127 m Ω ·cm. Film deposited at pH 7.8 has a smooth surface and definite columnar structure. The large wavy flakes were observed at pH 8.3. The high real part of complex permeability μ′ up to 36.1 and the imaginary part μ″ up to 53.2 were observed at 0.5 GHz by short microstrip line perturbation method. The μ″ of thin film has values higher than 20 at the frequencies between 0.5 GHz and 2 GHz, the film is a promising anti-noise material for high frequency applications,
文摘FeSiAl alloys ribbons synthesized by melt-quench were annealed in vacuum at 873 K for 60 rain. The flaky powders were prepared by milling the annealed ribbons for 70 h. After milling, the powders were heat treated at 573 K for 90 rain. The ordering degree of the powders lattice structure was analyzed by X-ray diffraction （XRD）. The measurement of specific saturation magnetization was carried out by vibrating samples magnetometer （VSM）. Complex permittivity and complex permeability in the frequency band of 0.5-18 GHz were measured with the vector network analyzer. The ordering degree of the superlattice structure increased from 0.2＇7 to 0.49. Complex permittivity and complex permeability decreased with increasing Si content. After ordering, the specific saturation magnetization decreased from 134.2 to 85.0 A.m2.kg-1. For use in anti-EMI material, the total contents of Si and Al in FeSiAl alloys should be controlled at a low level.
文摘The main focus of the research was to correlate the microstructure with dielectric and magnetic properties of Bi1-xBaxFeO3 samples. Bi1-xBaxFeO3 samples（x = 0.1, 0.2 and 0.3） were synthesized by the conventional solid-state reaction method using nano-powders of Bi2O3, Fe2O3, and BaCO3. Thereafter, field emission scanning electron microscope and X-ray diffraction（XRD） techniques were used to examine the structure and phase of the samples. Phase analysis by XRD indicated that the single-phase perovskite structure was formed with possible increment in lattice parameter with increasing Ba doping. Complex permeability（u＇iand u＇＇i） measured using impedance analyzer confirmed the increase in magnetic property with increasing Ba doping. Finally, dielectric constant（k） was analyzed as a function of temperature at different frequencies. Dielectric constant as high as 2900 was attained in this research for Bi0.8Ba0.2FeO3 sample due to reduction in leakage current at this composition.
文摘Spinel NiZn ferrite thin films were prepared on glass substrates by spray plating method. Adding cetyltrimethylammoniumchloride （CTAC）, adsorptive energy of substrate surface increased, and smooth surface and uniform columnar film structures were observed. The optimum reaction temperature up to 85℃ and pH up to 7.5 were obtained. As the solution pH value increases from 6.5 to 7.5, the film saturation magnetization increases to 36.1 and the imaginary part μ″ up to 53.2 for NiZn ferrite film at 500 MHz were achieved, and higher magnetic resonance at 508 MHz was observed. As the ferrite plate thickness is 50 μm, the attenuating characteristics for reflection loss ≤-0.8 dB can be obtained in the wide frequency ranging from 0.5 to 2.7 GHz. Theμ″ of thin film has values higher than 20 at the frequencies between 0.5 and 2 GHz, and the thin film can be applied as shielding material in GHz range.
基金Project supported by the National Natural Science Foundation of China （Grant No. 10774061）, the Defense Industrial Technology Development Program, China （Grant No. A1420080174）, and the Fundamental Research Funds for the Central Universities.
文摘The reflection properties of planar anisotropy FesoNiso powder/paraffin composites have been studied in the microwave frequency range. The permeability of Fe50Ni50 powder/paraffin composites is greatly enhanced by introducing the planar anisotropy, and can be further enhanced by using a rotational orientation method. The complex permeability can be considered as the superposition of two types of magnetic resonance. The resonance peak at high frequency is attributed to the natural resonance, while the peak at low frequency is attributed to the domain-wall resonance. The simulated results of the microwave reflectivity show that the matching thickness, peak frequency, permeability, and permittivity are closely related to the quarter wavelength matching condition. The Fe50Ni50 powder/paraffin composites can be attractive candidates for thinner microwave absorbers in the L-band （1-2 GHz）.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10774061)the Defense Industrial Technology Development Program,China (Grant No. A1420080174)the Fundamental Research Funds for the Central Universities
文摘The reflection properties of planar anisotropy Fe50Ni50 powder/paraffin composites have been studied in the microwave frequency range.The permeability of Fe50Ni50 powder/paraffin composites is greatly enhanced by introducing the planar anisotropy,and can be further enhanced by using a rotational orientation method.The complex permeability can be considered as the superposition of two types of magnetic resonance.The resonance peak at high frequency is attributed to the natural resonance,while the peak at low frequency is attributed to the domain-wall resonance.The simulated results of the microwave reflectivity show that the matching thickness,peak frequency,permeability,and permittivity are closely related to the quarter wavelength matching condition.The Fe50Ni50 powder/paraffin composites can be attractive candidates for thinner microwave absorbers in the L-band(1-2 GHz).
文摘Polycrystalline xBa<sub>0.95</sub>Sr<sub>0.05</sub>TiO<sub>3</sub>-(1 - x)BiFe<sub>0.90</sub>Gd<sub>0.10</sub>O<sub>3</sub> ceramics were prepared by standard solid state reaction technique using the solid solution of BaCO<sub>3</sub>, SrCO<sub>3</sub>, TiO<sub>2</sub>, Bi<sub>2</sub>O<sub>3</sub>, Fe<sub>2</sub>O<sub>3</sub> and Gd<sub>2</sub>O<sub>3</sub>. The compound is a BiFeO<sub>3</sub> based multiferroic material which contains both magnetic and electric properties. The synthesized ceramics noticed better properties than xBaTiO<sub>3</sub>-(1 - x)BiFeO<sub>3</sub> because of adding rare earth element Gd which have higher magnetic moment than Fe. The prepared samples were sintered at 900<span style="font-size:12px;white-space:nowrap;"><span style="font-size:12px;white-space:nowrap;">˚</span></span>C, 950<span style="font-size:12px;white-space:nowrap;"><span style="font-size:12px;white-space:nowrap;">˚</span></span>C and 1000<span style="font-size:12px;white-space:nowrap;"><span style="font-size:12px;white-space:nowrap;">˚</span></span>C for 1 h. The effect of sintering temperature on density of the compound, complex initial permeability, dielectric properties and complex impedance analysis was reported in this article. Density of the ceramics was found to be enhanced with the rise in sintering temperature which implied porosity of the compound decreased when sintering temperature was increased. Enhanced complex initial permeability was noticed for the samples up to 950<span style="font-size:12px;white-space:nowrap;"><span style="font-size:12px;white-space:nowrap;">˚</span></span>C and this might be attributed to reducing the motion of domain wall when the ceramics were sintered above 950<span style="font-size:12px;white-space:nowrap;"><span style="font-size:12px;white-space:nowrap;">˚</span></span>C. Value of dielectric constant increased whereas dielectric loss decreased and these modifications might be expected because of changing density and grain size due to the variation of sintering temperature. Grain resistance (resistance due to grains) was determined from complex impedance analysis and it reduced with the rise in sintering temperature. The studied multiferroic material exhibited weak ferromagnetism but is an alternative product of environmental hazard lead (Pb) based multiferroic material and it is expected to be environment friendly.
文摘The polycrystalline Li<em><sub>x</sub></em>Ni<sub>0.2</sub>Zn<sub>0.8-2</sub><em><sub>x</sub></em>Fe<em><sub>x</sub></em><sub>+2</sub>O<sub>4</sub> and Li<em><sub>x</sub></em>Ni<sub>0.1</sub>Cu<sub>0.1</sub>Zn<sub>0.8-2</sub><em><sub>x</sub></em>Fe<em><sub>x</sub></em><sub>+2</sub>O<sub>4</sub> (<em>x</em> = 0.0, 0.1, 0.2, and 0.3) ferrites were synthesized by the standard solid-state reaction method. The compound was sintered at 1150<span style="font-size:12px;white-space:nowrap;">˚</span>C for 5 hours. The effect of Cu substitution and its impact on the crystal structure, microstructure, complex initial permeability and magnetization of the Ni-Zn ferrites were studied. The effect of Li<sup>+</sup> incorporation on the properties mentioned above was also investigated. X-ray diffraction patterns of the samples indicated a single cubic spinel structure for both the compound. No effect of Cu addition on crystal structure was observed. The density of the ferrites was found to be enhanced because of adding Li whereas the porosity of the samples decreased with the content of Li ions. The average value of grain size increased with the addition of Li content. The samples having Cu ions formed bigger size grains. Frequency-dependent complex initial permeability, loss tangent, and relative quality factor were studied at room temperature using an Impedance analyzer in the range of 100 Hz - 120 MHz regions. In the low-frequency region, the prepared samples exhibited a high value of permeability and after a certain frequency, the permeability falls. The value of permeability enhanced with the increase in Li whereas loss tangent was found to be reduced. The relative quality factor graphs described that the compound has excellent frequency stability up to a certain frequency which is suitable to be used in inductors, resistors, capacitors, etc. Initial permeability for Li<em><sub>x</sub></em>Ni<sub>0.1</sub>Cu<sub>0.1</sub>Zn<sub>0.8-2</sub><em><sub>x</sub></em>Fe<em><sub>x</sub></em><sub>+2</sub>O<sub>4</sub> ferrites was found high than Li<em><sub>x</sub></em>Ni<sub>0.2</sub>Zn<sub>0.8-2</sub><em><sub>x</sub></em>Fe<em><sub>x</sub></em><sub>+2</sub>O<sub>4</sub> which might be attributed to having bigger size grains of Cu containing samples because of easy movement of domain wall in bigger size grains. The values of saturation magnetization (<em>M</em><sub>s</sub>) were calculated for both compounds from M-H hysteresis loops and it enhanced with the increase in Li content which might be related to the modification of predominant exchange interactions between the cations. The Cu-containing compound exhibited higher values of saturation magnetization. The cation distribution reflects this increment because ferromagnetic Ni<sup>2+</sup> and paramagnetic Cu<sup>2+</sup> ions occupied in the B-sites and the diamagnetic Zn and paramagnetic Li occupied in the A-sites;therefore, net magnetic moments increased gradually. The studied materials might be used as an alternative to Pb-based compounds and would be environment friendly.
基金supported by the National Key R&D Program of China(Grant No.2022YFB3804100)the National Natural Science Foundation of China(Grant No.52231005)the Science Technology Development Program of Yixing(Grant No.C2024002)。
文摘Soft magnetic composites(SMCs)play an indispensable role in electromagnetic conversion,transmission,and storage.However,achieving high-frequency,low-loss soft magnetic materials compatible with third-generation wide bandgap semiconductor devices remains a significant challenge.In this study,we report a novel strategy to fabricate Fe-based amorphous SMCs through a precisely controlled phosphating process.As the phosphoric acid content increases,the thickness of the insulating layer increases,resulting in higher resistivity.At the same time,the contribution of spin rotation to magnetization increases gradually and dominates throughout the magnetization.Compared with the untreated SMCs,the core loss(P_(cv))of the SMCs treated with 1.0 wt.%phosphoric acid at 0.1 T/1 MHz was reduced by 11.6%,primarily due to the reduction of excess losses resulting from the different magnetization mechanisms.The optimized SMCs demonstrate outstanding overall magnetic performance,including ultra-low P_(cv)of 14.35 W/cm^(3)at 0.1 T/1 MHz,excellent DC-bias stability(69.4%at 100 Oe),relatively high saturation magnetic flux density(B_(s)=0.84 T),and ultra-stable permeability(μ_(e)=32.7)up to 20 MHz.These findings offer a promising pathway for designing high-performance SMCs tailored for high-frequency and high-power electronic applications.
基金The Innovation Fund Project of China Electric Power Research Institute:Research on accuracy test method of voltage transformer for low-frequency transmission and development of test system,Grant/Award Number:GY83-22-005。
文摘To address the lack of voltage ratio standards for accuracy testing of low-frequency voltage transformers,it is necessary to develop a 3 kV low-frequency induction voltage divider.Firstly,based on the analysis of the error sources of the induction voltage divider,a method was proposed to calculate the excitation impedance of the induction voltage divider using complex magnetic permeability.A measurement circuit based on the lock-in principle was set up to measure the complex magnetic permeability of grained-oriented silicon steel 30P100 and permalloy 1J85 at different frequencies.Secondly,a 3 kV low-frequency induction voltage divider with a two-stage excitation and a series-wound ra-tio winding in 10 sections was designed.The errors of the two stages of the instrument transformers were calculated at 20 and 50 Hz,respectively.Finally,the divider's errors were calibrated at 20 and 50 Hz using the reference potential method.The results showed that,compared to 50 Hz,the excitation impedance of the two stages decreased and the errors increased at 20 Hz,with the overall error of the induction voltage divider being better at 50 Hz than at 20 Hz.Experimental measurements indicated that at 20 Hz,the ratio error and phase error of the 3 kV two-stage excitation induction voltage divider were better than 110-5,whereas at 50 Hz,the errors were better than 110-6.This study provides support for the accuracy testing of voltage transformers used in low-frequency flexible AC transmission projects.
基金supported by the Natural Science Fund of China(51762023)the JiangXi Association for Science and Technology,the Jiangxi Provincial Department of Education,and the Training Program of Outstanding Young Scientists in Jiangxi Province(20171BCB23070).
文摘Magnetic,dielectric and DC conductive properties of Ni_(0.95-x)Zn_(x)Co_(0.05)Fe_(1.90)Mn_(0.02)O_(4)(with x=0-0.20 at an interval of 0.05)ferrite ceramics were studied,in order to develop magneto-dielectric materials with almost equal values of relative permeability and permittivity,for the miniaturization of HF(3-30 MHz)and VHF(30-90MHz and 100-300 MHz)antennas.The ferrite ceramics were prepared by using the conventional two-step sintering process.The real part of relative permeability is increased almost linearly with increasing concentration of Zn,while that of relative permittivity keeps nearly unchanged.It is found that promising magneto-dielectric materials,with close values of real permeability and permittivity over 30-90 MHz(VHF),can be obtained for the samples at Zn concentrations between x=0.05 and x=0.10.
