Microspheres of Ni_(0.5)Co_(0.5)Ga_(x)Fe_(2-x)O_(4)(x≤1.0)microsphere spinel ferrites(NiCoGaFe-MSFs)and carbon spheres were prepared via a hydrothermal technique.The micro structure of microspheres was investigated t...Microspheres of Ni_(0.5)Co_(0.5)Ga_(x)Fe_(2-x)O_(4)(x≤1.0)microsphere spinel ferrites(NiCoGaFe-MSFs)and carbon spheres were prepared via a hydrothermal technique.The micro structure of microspheres was investigated through scanning and transmission electron microscopy(SEM and TEM),respectively,and X-ray diffraction(XRD).The electrical and dielectric properties of NiCoGaFe-MSF at temperatures ranging from20 to 120℃(between 293,1×10^(3)and 393.1×10^(3))for f≤3.0 MHz were systematically studied as a result of 3D graphical drawing of the data obtained from an impedance analyzer.Relevant parameters such as ac/dc conductivity,dielectric loss,dielectric constant,activation energy,dissipation factor and Cole-Cole impedance spectra were extensively evaluated for various Ga ion mole ratios in the substitution where x≤1.0.We notice that the ac conductivity mostly obeys exponential power law rules,which vary significantly with the substitution ratios of Ga ions.Impedance analyses confirm that differences in conduction mechanisms in NiCoGaFe-MSFs are mainly due to grain-to-grain boundaries related to Ga ion substitution ratios.The change in dielectric constant of NiCoGaFe-MSFs is strongly dependent on the substitution rates and results in a normal dielectric distribution with frequency.The tangential loss for all micro spheres is observed to vary with measured temperatures and their frequency dependencies can be attributed to the conduction mechanism similar to Koop’s phenomenological model.It is clearly seen that the formation of semicircles is dominated by all the NiCoGaFe-MSFs and the diameter of the semicircles mostly decreases with increasing temperature,as evidence of a temperaturedependent relaxation mechanism.展开更多
The impact of Ga^(3+)and Gd^(3+)co-substitution on different types of behavior of Ni-Co nanospinel ferrites(NSFs),(Ni_(0.5)Co_(0.5))[Ga_(x)Gd_(x)Fe_(2-2x)]O_(4)(0.000≤x≤0.025),was investigated.NSFs were fabricated t...The impact of Ga^(3+)and Gd^(3+)co-substitution on different types of behavior of Ni-Co nanospinel ferrites(NSFs),(Ni_(0.5)Co_(0.5))[Ga_(x)Gd_(x)Fe_(2-2x)]O_(4)(0.000≤x≤0.025),was investigated.NSFs were fabricated through ultrasound irradiation.The structure,composition,and spherical morphology of all products were verified by numerous characterization techniques such as X-ray diffraction(XRD),scanning and transmission electron microscopes(SEM and TEM),and selected area electron diffraction(SAED).Mossbauer spectra are composed of two ferromagnetic sextets and one paramagnetic doublet.These spectra were fitted to extract hyperfine parameters of the doped samples.Both sublattices'hyperfine magnetic field decreases with substitution.The isomer shift values show that the Mossbauer spectra are composed of magnetic Fe^(3+)sextets.The magnetization measurements at variable magnetic field(M-H)were investigated via a vibrating sample magnetometer(VSM)at temperatures(T)from 300 to 10 K.All NSFs disclose ferrimagnetic behavior at both 300 and 10 K at which they are soft and hard,respectively.We determined that the remanence magnetization(M_(r)),saturation magnetization(M_(s)),and magneton number(n_(B))decrease with increasing Ga^(3+)and Gd^(3+)ions contents.The reduction in these values is predominantly recognized to be the impact of cation redistribution and surface spins on tetrahedral(T_(d))and octahedral(O_(h))sites.As the Ga^(3+)and Gd^(3+)contents increase,the coercivity(H_(c))is also found to decrease.展开更多
文摘Microspheres of Ni_(0.5)Co_(0.5)Ga_(x)Fe_(2-x)O_(4)(x≤1.0)microsphere spinel ferrites(NiCoGaFe-MSFs)and carbon spheres were prepared via a hydrothermal technique.The micro structure of microspheres was investigated through scanning and transmission electron microscopy(SEM and TEM),respectively,and X-ray diffraction(XRD).The electrical and dielectric properties of NiCoGaFe-MSF at temperatures ranging from20 to 120℃(between 293,1×10^(3)and 393.1×10^(3))for f≤3.0 MHz were systematically studied as a result of 3D graphical drawing of the data obtained from an impedance analyzer.Relevant parameters such as ac/dc conductivity,dielectric loss,dielectric constant,activation energy,dissipation factor and Cole-Cole impedance spectra were extensively evaluated for various Ga ion mole ratios in the substitution where x≤1.0.We notice that the ac conductivity mostly obeys exponential power law rules,which vary significantly with the substitution ratios of Ga ions.Impedance analyses confirm that differences in conduction mechanisms in NiCoGaFe-MSFs are mainly due to grain-to-grain boundaries related to Ga ion substitution ratios.The change in dielectric constant of NiCoGaFe-MSFs is strongly dependent on the substitution rates and results in a normal dielectric distribution with frequency.The tangential loss for all micro spheres is observed to vary with measured temperatures and their frequency dependencies can be attributed to the conduction mechanism similar to Koop’s phenomenological model.It is clearly seen that the formation of semicircles is dominated by all the NiCoGaFe-MSFs and the diameter of the semicircles mostly decreases with increasing temperature,as evidence of a temperaturedependent relaxation mechanism.
文摘The impact of Ga^(3+)and Gd^(3+)co-substitution on different types of behavior of Ni-Co nanospinel ferrites(NSFs),(Ni_(0.5)Co_(0.5))[Ga_(x)Gd_(x)Fe_(2-2x)]O_(4)(0.000≤x≤0.025),was investigated.NSFs were fabricated through ultrasound irradiation.The structure,composition,and spherical morphology of all products were verified by numerous characterization techniques such as X-ray diffraction(XRD),scanning and transmission electron microscopes(SEM and TEM),and selected area electron diffraction(SAED).Mossbauer spectra are composed of two ferromagnetic sextets and one paramagnetic doublet.These spectra were fitted to extract hyperfine parameters of the doped samples.Both sublattices'hyperfine magnetic field decreases with substitution.The isomer shift values show that the Mossbauer spectra are composed of magnetic Fe^(3+)sextets.The magnetization measurements at variable magnetic field(M-H)were investigated via a vibrating sample magnetometer(VSM)at temperatures(T)from 300 to 10 K.All NSFs disclose ferrimagnetic behavior at both 300 and 10 K at which they are soft and hard,respectively.We determined that the remanence magnetization(M_(r)),saturation magnetization(M_(s)),and magneton number(n_(B))decrease with increasing Ga^(3+)and Gd^(3+)ions contents.The reduction in these values is predominantly recognized to be the impact of cation redistribution and surface spins on tetrahedral(T_(d))and octahedral(O_(h))sites.As the Ga^(3+)and Gd^(3+)contents increase,the coercivity(H_(c))is also found to decrease.
