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
Nanocrystalline Ni0.5Zn0.5 ferrite with average grain sizes ranging from 10 to 100 nm is prepared by using a spraying-coprecipitation method. The results indicate that the nanocrystalline Ni0.5Zn0.5 ferrite is ferroma...Nanocrystalline Ni0.5Zn0.5 ferrite with average grain sizes ranging from 10 to 100 nm is prepared by using a spraying-coprecipitation method. The results indicate that the nanocrystalline Ni0.5Zn0.5 ferrite is ferromagnetic without the superparamagnetic phenomenon observed at room temperature. Specific saturation magnetization of nanocrystalline Nio.sZno.5 ferrite increases from 40.2 to 75.6 emu/g as grain size increases from 11 to 94nm. Coercivity of nanocrystalline Ni0.5Zn0.5 ferrite increases monotonically when d 〈 62 nm.The relationship between the coercivity and the mean grain size is well fitted into a relation Hc - d^3. A theoretically evaluated value of the critical grain size is 141nm larger than the experimental value 62nm for nanocrystalline Ni0.5Zn0.5 ferrite. The magnetic behaviour of nanocrystalline Ni0.5Zn0.5 ferrite may be explained by using the random anisotropy theory.展开更多
Ultrafine Ni0.5Zn0.5 Fe2O4 powder was prepared by PVA aided chemical method. The powder and sintered pellets were characterised by X-ray diffraction (XRD), vibrating sample magnetometry (VSM), thermogravimetric analys...Ultrafine Ni0.5Zn0.5 Fe2O4 powder was prepared by PVA aided chemical method. The powder and sintered pellets were characterised by X-ray diffraction (XRD), vibrating sample magnetometry (VSM), thermogravimetric analysis (TGA) and complex impedance (Cl) analysis. The particles are found to be in the size range of 15 to 26 nm for various annealing temperatures. The coercivity, saturation magnetisation, Neel temperature and electrical conductivity are found to vary with sintering time at 800℃ for the pellet samples. The variations in the above intrinsic properties are explained qualitatively展开更多
Powder mixtures of Zn, NiO, and Fe2O3 are mechanically alloyed by high energy ball milling to produce Ni-Zn ferrite with a nominal composition of Ni0.36Zn0.64Fe2O4. The effects of milling atmospheres （argon, air, and...Powder mixtures of Zn, NiO, and Fe2O3 are mechanically alloyed by high energy ball milling to produce Ni-Zn ferrite with a nominal composition of Ni0.36Zn0.64Fe2O4. The effects of milling atmospheres （argon, air, and oxygen）, milling time （from 0 to 30 h） and heat treatment are studied. The products are characterized using x-ray diffractometry, field emission scanning electron microscopy equipped with energy-dispersive x-ray spectroscopy, and transmitted electron microscopy. The results indicate that the desired ferrite is not produced during the milling in the samples milled under either air or oxygen atmospheres. In those samples milled under argon, however, Zn/NiO/Fe2O3 reacts with a solid-state diffusion mode to produce Ni-Zn ferrite nanocrystalline in a size of 8 nm after 30-h-milling. The average crystallite sizes decrease to 9 nm and 10 nm in 30-h-milling samples under air and oxygen atmospheres, respectively. Annealing the 30-h-milling samples at 600℃ for 2 h leads to the formation of a single phase of Ni-Zn ferrite, an increase of crystallite size, and a reduction of internal lattice strain. Finally, the effects of the milling atmosphere and heating temperature on the magnetic properties of the 30-h-milling samples are investigated.展开更多
Nanocrystalline Ni1-xZnxFe2O4 ferrites with 0≤x≤1 were successfully prepared by a spraying-coprecipitation method.The microstructure was investigated by using XRD and TEM.Magnetic properties were measured with vibra...Nanocrystalline Ni1-xZnxFe2O4 ferrites with 0≤x≤1 were successfully prepared by a spraying-coprecipitation method.The microstructure was investigated by using XRD and TEM.Magnetic properties were measured with vibrating sample magnetometer（VSM） at room temperature.The results show that the grain size of nanocrystalline Ni1-xZnxFe2O4 ferrite calcined at 600 ℃ for 1.5 h is about 30 nm.Lattice parameter and specific saturation magnetization Ms of nanocrystalline Ni1-xZnxFe2O4 ferrite increase with the Zn^2＋ ions content at room temperature,and maximum Ms is 66.8 A·m^2·kg^-1 as the Zn^2＋ ions content is around 0.5,and coercivity Hc of the nanocrystalline Ni1-xZnxFe2O4 ferrite decreases with Zn^2＋ ions content.展开更多
Aluminium doped Ni-Zn ferrite nanoparticles of general formula of Ni0.5Zn0.5AlxFe2-xO4 (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, 2.0) have been synthesized by sol-gel auto combustion method and characteri...Aluminium doped Ni-Zn ferrite nanoparticles of general formula of Ni0.5Zn0.5AlxFe2-xO4 (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, 2.0) have been synthesized by sol-gel auto combustion method and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dis-persive X-ray (EDX), Fourier transform spectroscopy (FTIR) and vibrating sample magneto meter (VSM). XRD studies confirm that all compositions show single phase cubic spinel structure. The crystallite size was calculated using the Debye-Scherrer formula and found in the range of 17 - 52 nm. The lattice parameter “a” is found to decrease with increasing Al3+ content. The SEM images clearly show the crystalline structure and EDX patterns confirm the compositional formation of the synthesized compositions. The results of FTIR analysis indicated that the functional groups of Ni-Zn spinel ferrite were formed during the sol-gel synthesis process. The IR spectra showed two main absorption bands, the high frequency band ν1 around 600 cm-1 and the low frequency band ν2 around 400 cm-1 arising from tetrahedral (A) and octahedral (B) interstitial sites in the spinel lattice. As doping is increased the magnetic behavior is found to decrease and the composition x = 2.0 ferrite appears to be exhibiting superparamagnetism as the coercive field and retentivity are found near zero.展开更多
Ni-Zn ferrite with a nominal composition of Ni1-xZnxFe2O4 (x = 0, 0.2, 0.6, 0.8, 0.9) are prepared by citrate gel method and characterized by X-ray diffraction. Magnetic properties of all samples are obtained by using...Ni-Zn ferrite with a nominal composition of Ni1-xZnxFe2O4 (x = 0, 0.2, 0.6, 0.8, 0.9) are prepared by citrate gel method and characterized by X-ray diffraction. Magnetic properties of all samples are obtained by using VSM (Vibrating Sample Magnetometer) in the range of 10 Koe. The saturation magnetization values of the samples are carried out from the B-H loop. The effect of composition on saturation magnetization and magnetic moment are studied in this paper. The results showed that Saturation magnetization and magnetic moment values increases gradually as Zn2+ composition increases, it reaches maximum value 70.28 emu/gm for (x = 0.6) and decreases further with increasing Zn2+ composition.展开更多
The optimum ferrite can be obtained through free-microstructural defects where such defects are always encountered in the conventional ferrites often caused by chemical inhomogeneity. In this study, Ni-Zn ferrite was ...The optimum ferrite can be obtained through free-microstructural defects where such defects are always encountered in the conventional ferrites often caused by chemical inhomogeneity. In this study, Ni-Zn ferrite was synthesized and fabricated by means of a sol-gel route. Thermal gravimetric analysis (TGA) was used to study the thermal transforma-tion of the ferrite in air. Parts of the sol-gel powder heated at elevated temperatures were characterized by X-ray dif-fraction (XRD) method and Scanning Electron Microscopy (SEM) to reveal the crystallized single-phase and the struc-ture of the obtained ferrite. Fourier transform infrared spectroscopy (FT-IR) was assisted to investigate the structure. The microstructures of the toroidal cores were obtained at two different sintering temperatures and compared with those obtained via the classic method. In addition to that, the magnetic properties were measured. The initial magnetic permeability was found to increase with the increasing of the frequency as a result of the domain wall motions and the corresponding loss was small. Therefore, a well defined polycrystalline microstructure ferrite via an easier preparation methodology as compared to the classic method is obtained.展开更多
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.
文摘Nanocrystalline Ni0.5Zn0.5 ferrite with average grain sizes ranging from 10 to 100 nm is prepared by using a spraying-coprecipitation method. The results indicate that the nanocrystalline Ni0.5Zn0.5 ferrite is ferromagnetic without the superparamagnetic phenomenon observed at room temperature. Specific saturation magnetization of nanocrystalline Nio.sZno.5 ferrite increases from 40.2 to 75.6 emu/g as grain size increases from 11 to 94nm. Coercivity of nanocrystalline Ni0.5Zn0.5 ferrite increases monotonically when d 〈 62 nm.The relationship between the coercivity and the mean grain size is well fitted into a relation Hc - d^3. A theoretically evaluated value of the critical grain size is 141nm larger than the experimental value 62nm for nanocrystalline Ni0.5Zn0.5 ferrite. The magnetic behaviour of nanocrystalline Ni0.5Zn0.5 ferrite may be explained by using the random anisotropy theory.
文摘Ultrafine Ni0.5Zn0.5 Fe2O4 powder was prepared by PVA aided chemical method. The powder and sintered pellets were characterised by X-ray diffraction (XRD), vibrating sample magnetometry (VSM), thermogravimetric analysis (TGA) and complex impedance (Cl) analysis. The particles are found to be in the size range of 15 to 26 nm for various annealing temperatures. The coercivity, saturation magnetisation, Neel temperature and electrical conductivity are found to vary with sintering time at 800℃ for the pellet samples. The variations in the above intrinsic properties are explained qualitatively
基金Project supported by the University Putra Malaysia Graduate Research Fellowship Section
文摘Powder mixtures of Zn, NiO, and Fe2O3 are mechanically alloyed by high energy ball milling to produce Ni-Zn ferrite with a nominal composition of Ni0.36Zn0.64Fe2O4. The effects of milling atmospheres （argon, air, and oxygen）, milling time （from 0 to 30 h） and heat treatment are studied. The products are characterized using x-ray diffractometry, field emission scanning electron microscopy equipped with energy-dispersive x-ray spectroscopy, and transmitted electron microscopy. The results indicate that the desired ferrite is not produced during the milling in the samples milled under either air or oxygen atmospheres. In those samples milled under argon, however, Zn/NiO/Fe2O3 reacts with a solid-state diffusion mode to produce Ni-Zn ferrite nanocrystalline in a size of 8 nm after 30-h-milling. The average crystallite sizes decrease to 9 nm and 10 nm in 30-h-milling samples under air and oxygen atmospheres, respectively. Annealing the 30-h-milling samples at 600℃ for 2 h leads to the formation of a single phase of Ni-Zn ferrite, an increase of crystallite size, and a reduction of internal lattice strain. Finally, the effects of the milling atmosphere and heating temperature on the magnetic properties of the 30-h-milling samples are investigated.
基金Funded by the Natural Science Foundation of High Education School ofAnhui Province,China (Nos:KJ2007B0271 and KJ2010A095)
文摘Nanocrystalline Ni1-xZnxFe2O4 ferrites with 0≤x≤1 were successfully prepared by a spraying-coprecipitation method.The microstructure was investigated by using XRD and TEM.Magnetic properties were measured with vibrating sample magnetometer（VSM） at room temperature.The results show that the grain size of nanocrystalline Ni1-xZnxFe2O4 ferrite calcined at 600 ℃ for 1.5 h is about 30 nm.Lattice parameter and specific saturation magnetization Ms of nanocrystalline Ni1-xZnxFe2O4 ferrite increase with the Zn^2＋ ions content at room temperature,and maximum Ms is 66.8 A·m^2·kg^-1 as the Zn^2＋ ions content is around 0.5,and coercivity Hc of the nanocrystalline Ni1-xZnxFe2O4 ferrite decreases with Zn^2＋ ions content.
文摘Aluminium doped Ni-Zn ferrite nanoparticles of general formula of Ni0.5Zn0.5AlxFe2-xO4 (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, 2.0) have been synthesized by sol-gel auto combustion method and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dis-persive X-ray (EDX), Fourier transform spectroscopy (FTIR) and vibrating sample magneto meter (VSM). XRD studies confirm that all compositions show single phase cubic spinel structure. The crystallite size was calculated using the Debye-Scherrer formula and found in the range of 17 - 52 nm. The lattice parameter “a” is found to decrease with increasing Al3+ content. The SEM images clearly show the crystalline structure and EDX patterns confirm the compositional formation of the synthesized compositions. The results of FTIR analysis indicated that the functional groups of Ni-Zn spinel ferrite were formed during the sol-gel synthesis process. The IR spectra showed two main absorption bands, the high frequency band ν1 around 600 cm-1 and the low frequency band ν2 around 400 cm-1 arising from tetrahedral (A) and octahedral (B) interstitial sites in the spinel lattice. As doping is increased the magnetic behavior is found to decrease and the composition x = 2.0 ferrite appears to be exhibiting superparamagnetism as the coercive field and retentivity are found near zero.
文摘Ni-Zn ferrite with a nominal composition of Ni1-xZnxFe2O4 (x = 0, 0.2, 0.6, 0.8, 0.9) are prepared by citrate gel method and characterized by X-ray diffraction. Magnetic properties of all samples are obtained by using VSM (Vibrating Sample Magnetometer) in the range of 10 Koe. The saturation magnetization values of the samples are carried out from the B-H loop. The effect of composition on saturation magnetization and magnetic moment are studied in this paper. The results showed that Saturation magnetization and magnetic moment values increases gradually as Zn2+ composition increases, it reaches maximum value 70.28 emu/gm for (x = 0.6) and decreases further with increasing Zn2+ composition.
文摘The optimum ferrite can be obtained through free-microstructural defects where such defects are always encountered in the conventional ferrites often caused by chemical inhomogeneity. In this study, Ni-Zn ferrite was synthesized and fabricated by means of a sol-gel route. Thermal gravimetric analysis (TGA) was used to study the thermal transforma-tion of the ferrite in air. Parts of the sol-gel powder heated at elevated temperatures were characterized by X-ray dif-fraction (XRD) method and Scanning Electron Microscopy (SEM) to reveal the crystallized single-phase and the struc-ture of the obtained ferrite. Fourier transform infrared spectroscopy (FT-IR) was assisted to investigate the structure. The microstructures of the toroidal cores were obtained at two different sintering temperatures and compared with those obtained via the classic method. In addition to that, the magnetic properties were measured. The initial magnetic permeability was found to increase with the increasing of the frequency as a result of the domain wall motions and the corresponding loss was small. Therefore, a well defined polycrystalline microstructure ferrite via an easier preparation methodology as compared to the classic method is obtained.
