Synthesis and Characterization of Ni0.7Zn0.3Fe2O4 and Mn0.7Zn0.3Fe2O4 Nanoparticles by Water-in-oil Microemulsion

Ferrite is an important ceramic material with magnetic properties that are useful in many types of electronic devices. In this paper we synthesized nanostructured Ni_0.7Zn_0.3Fe₂O₄ and Mn_0.7Zn_0.3Fe₂O₄ with spinel structure in the system of water-in-oil microemulsion of water/Triton X–100/n-hexanol/cyclohexane. The result showed that nanoparticles with size in the range of 50–80 nm could be obtained by microemulsion method. FT-IR spectrum, XRD patterns and DTA curves revealed that the nanoparticles could be obtained via calcining its precursor at 500°C. The VSM plots showed that the ferrimagnetic behavior was expected for this type of magnetic material.     

Synthesis of monodispersed pH-sensitive Ni0.5Zn0.5Fe2O4 magnetic nanoparticles and the potential medical application of adsorption for bovine serum album

We synthesized Ni_0.5Zn_0.5Fe₂O₄ magnetic nanoparticles (MNPs) by co-precipitation method and performed its adsorption of bovine serum albumin V(BSA (V)). The Ni_0.5Zn_0.5Fe₂O₄ MNPs in nitrogen atmosphere annealed at 400, 500, 600, 700 and 800°C, respectively. X-ray diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometer(VSM) were used to characterize the resulting powders of the structure and properties. XRD results show that the Ni_0.5Zn_0.5Fe₂O₄ powder is a typical single-phase cubic spinel structure, and has no impurity phases. TEM results show that the Ni_0.5Zn_0.5Fe₂O₄ crystalline size is approximately 30–50 nm, which is similar with the XRD estimate results. The magnetic measurements show that Ni_0.5Zn_0.5Fe₂O₄ samples, super paramagnetic material, have high saturation magnetization and small coercivity properties. Moreover, We adopted ultraviolet spectrophotometer to analysis adsorption of BSA(V) on the Ni_0.5Zn_0.5Fe₂O₄ MNPs at room temperature, which show that annealed temperatures, pH, and stirring time can affect BSA(V) adsorption on the Ni_0.5Zn_0.5Fe₂O₄ MNPs. Most importantly, when ultrasonic stirring 2 hours in the liquor BSA(V) at pH = 7.0, the Ni_0.5Zn_0.5Fe₂O₄ samples annealed at 600°C has a highest value of 39.81mgg^?1. From above these results, Ni_0.5Zn_0.5Fe₂O₄ MNPs reveals a great adsorbing ability for BSA(V) that probable are a potential BSA-carrier candidate.     

Magnetic properties of Ni-Zn ferrites prepared by microwave sintering method

The effect of zinc ion substitution for nickel on structural and magnetic properties of NiZn ferrites is reported. The spinel ferrite system Ni_1-xZn_xFe₂O₄ with x = 0.2, 0.3, 0.4 and 0.5 was prepared by microwave sintering method. The uniaxially pressed samples were sintered at various temperatures such as 900°C, 1000°C and 1100°C for 30 min. X-ray diffraction patterns of the samples indicate the formation of single-phase cubic spinel structure. SEM micrographs show that grain size increases with increasing zinc content and sintering temperature. The elemental composition of these ferrites was analyzed by EDS. Lattice constant increases with increase in zinc content, obeying Vegard’s law. The effect of composition and sintering temperature on initial permeability as the function of frequency and temperature was studied. The initial permeability of NiZn ferrite increases greatly with increasing Zn content and sintering temperature. The dependence of initial permeability with respect to temperature shows the decrease in the Curie point with increase in zinc content, is the normal behavior of ferrites. The relative loss factor (tand

Cation distribution and magnetic behavior of Mg1 − x Zn x Fe2O4 ceramics monitored by Mössbauer Spectroscopy

The properties of magnesium ferrites, Mg_{1 ? x} Zn _x Fe₂O₄ with 0.0 ≤ x ≤ 0.5, were investigated by means of powder X-ray diffraction, magnetization, Mössbauer spectroscopy, and scanning electron microscopy. The ferrites were prepared by conventional solid-state reaction using a mixed oxide method. All XRD patterns revealed only the monophasic spinel characteristic structure of MgFe₂O₄. The lattice parameters increased with the increasing of Zn content. Saturation magnetization (M _S ) of the ferrites was discussed with respect to Zn substitution. M _S values increased with Zn content up to x = 0.35 and then decreased thereafter. Mössbauer results showed Fe^{3 +} ion distribution between tetrahedral and octahedral sites and the effect of Zn ions on ferrimagnetic order. The line-broadening of the Mössbauer spectra increased with substituting Mg with Zn ions due to disruption of the local magnetic order. The SEM micrographs of the sintered bodies showed irregular shape in the order of ～5–6 μm.     

The effect of Sb on the electrical and magnetic properties of Ni-Zn ferrites prepared by sol–gel autocombustion method

Polycrystalline Ni-Zn ferrites with a well-defined composition of Ni_0.4Zn_0.6Fe_2-xSb_xO₄ synthesized using sol–gel method. Morphological characterizations on the prepared samples were performed by high resolution transmission electron and field emission scanning electron microscopy. The powders were densified using microwave sintering method. The room temperature complex permittivity (ε′ and ε″) and permeability (μ′ and μ″) were measured over a wide frequency range from 1 MHz–1.8 GHz. The real part of permittivity varies as ‘x’ concentration increases and the resonance frequency was observed at much higher frequencies and there is a significant decrease in the loss factor (tanδ). The electrical resistivity and permeability of NiZn ferrites increased with an increase of Sb content. As the concentration of ‘x’ increases from 0 to 0.08 the saturation magnetisation decreases. The saturation magnetization (M_s)?≈?52.211 A.m²/Kg for x?=?0 at room temperature. The room temperature electro paramagnetic resonance (EPR) were studied.     

Effect of Co-substitution on the structure and magnetic properties of MnZn power ferrite

MnZn power ferrites with a composition of Mn_0.681-xZn_0.246Fe_2.073Co_xO₄ were prepared by conventional ceramic technique. The samples were sintered in a computer-driven furnace at 1320 °C for 4 h. Then the influences of Co-substitution on the crystalline structure, microstructure and the magnetic properties of MnZn power ferrite were studied. It shows that Co-substitution has not changed the structure of MnZn ferrite, but improved the crystallization. With the increase of Co substitution content, Co²⁺ ions firstly replace Mn²⁺ ions and then replace Fe³⁺ ions. And at room temperature, the initial permeability increases with the increase of Co-substitution content. Co-substitution can also reduce the porosity and the power loss. In addition, the corresponding temperature of the minimum power loss shifts to a lower temperature.     

Ni-Zn ferrite films synthesized from aqueous solution usable for sheet-type conducted noise suppressors in GHz range

Ni_0.2Zn_0.3Fe_2.5O₄ films (1–5 μm thick) were deposited by spin spray ferrite plating from an aqueous solutions onto polyimide sheets at 90^∘C. Their peel test and high-frequency permeability as well as noise suppression effects were investigated. The oxygen plasma treatment on polyimide sheet surface improved the film adhesion. There was not visible crack on the bended film surface for the Ni-Zn ferrite film thinner than 2 μm and was not peeled off even after the bending test of a million times. The films exhibited excellent high-frequency permeability profile and a natural resonance frequency (where the imaginary permeability reaches a maximum) f _r was 370 ± 30 MHz. The transmission loss increased with the film thickness, reaching the maximum Δ P _loss = 70% at 8 GHz for the 5 μm-thick film. The reflection loss in the measured frequency range was S ₁₁ < 10 % which is small enough for films to be used as the conducted noise suppressors. The value of Δ P _loss obtained for the 5-μm thick film was about 15% higher than that (Δ P _loss = 55 %) attained by the commercialized 50-μm thick noise suppressing sheet.     

Ni–Mn–Fe–Cr–O negative temperature coefficient thermistor compositions: Correlation between processing conditions and electrical characteristics

A study has been carried out to correlate the effect of sintering temperature on the microstructural, electrical and reliability aspects of Ni_0.75Mn_{(2.25−x−y)}Cr _x Fe _y O₄ (x = 0 to 0.3 and y = 0 to 0.3) negative temperature coefficient thermistor compositions prepared by solid-state route. The calcined and sintered compositions were characterized by X-ray diffraction and Scanning Electron Microscopy. The existence of cubic spinel single-phase region was determined by sintering Ni_0.75Mn_{(2.25−x−y)}Cr _x Fe _y O₄ samples in air at temperatures 1150 to 1250 °C. X-ray diffraction patterns of samples sintered above 1200 °C shows additional Bragg reflections of a rock salt structured NiO phase besides normal cubic spinel. A maximum B-value of 4044 K was obtained for Ni_0.75Mn_1.95Cr_0.25Fe_0.05O₄ composition at a sintering temperature 1250 °C/3 h. The reliability of the thermistor compositions were evaluated by performing accelerated ageing based on thermal cycling test. We found that chromium enhances the reliability of Ni_0.75Mn_{(2.25−x−y)}Cr _x Fe _y O₄ (x = 0 to 0.3 and y = 0 to 0.3) based NTC thermistor compositions. A maximum reliability of +0.25% resistance drift was observed at sintering temperature 1200 °C for 0.25 mol% chromium content. Excellent reliability of Ni_0.75Mn_{(2.25−x−y)}Cr _x Fe _y O₄ NTC thermistor compositions makes it ideal candidates for high-performance thermal sensor applications.     

Investigations of lanthanum doping on magnetic properties of nano cobalt ferrites

The magnetic properties of nano-crystallite cobalt lanthanum ferrite (CoLa_xFe_2-x O₄) with varied quantities of lanthanum (x = 0, 0.1, 0.15, 0.2, 0.25, 0.3) prepared by co-precipitation method have been studied by vibrating sample magnetometer (VSM) and LCR meter. X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed the size, structure, and morphology of the ferrite samples. The average crystallite size varied from 17.83 nm to 49.99 nm. All the samples, although, in nano range, show significant hysteresis. The saturation magnetization (M_s) values decreased from 60.57 emu/g to 30.15 emu/g. The remanence (M_R) fell from 10.85 emu/g to 6.39 emu/g. Doping with lanthanum La³⁺ ions modulates significantly the magnetic properties of cobalt spinel ferrites without sacrificing the ferromagnetic character.     

Thermal Conductivity of Nano ZnO Doped CaFe2O4

The research objective of this study was to examine whether Zn was an effective doping element for thermal conductivity. Ca_1-xZn_xFe₂O₄ (x = 0.0–0.5) were synthesized by solid state reaction method. The XRD results showed that all samples were mixed phase of CaFe₂O₄ and ZnFe₂O₄. The structure of Ca_1-xZn_xFe₂O₄ (x = 0.0–0.5) belonged to a group of an orthorhombic system (space group: Pbnm). It was observed that all the samples of Ca_1-xZn_xFe₂O₄ (x = 0.0–0.5) had positive Seebeck coefficient as shown on p-type semiconductor behavior. Thus thermal conductivity tended to decrease with increasing x value. The Ca_0.6Zn_0.4Fe₂O₄ showed lowest thermal conductivity of 6.52 W m^?1 K^?1 at 473 K, which was lower than 50.81% of CaFe₂O₄. These results suggested that Zn was an effective doping element for improving the thermal conductivity of Ca_1-xZn_xFe₂O₄.     

Magnetic properties of ZnO-doped cobalt ferrite

The cobalt ferrites with chemical composition Co_1+x Zn _x Fe_2?2x O₄ (x?=?0.0, 0.1, 0.2, 0.4) were obtained with conventional solid reaction. The ZnO-doped samples have lower lattice constant than CoFe₂O₄ by adjusting Co ions to the octahedral sites. The results show that doping ZnO could extremely improve the magnetic properties. In comparison with pure CoFe₂O₄, the little ZnO-doped sample has higher permeability and much lower coercivity at the condition of a little decrease of magnetization saturation. Sample with x?=?0.1 shows evident magnetostrictive effect at the magnetic field of 30–60 mT while pure cobalt ferrite sample does not, though the saturation magnetostriction decreases. These indicate that ZnO-doping improves the magnetostrictive sensitivity of the cobalt ferrites and have potential applications in magnetoelectric devices and magnetic detector.     

Dielectric,ferroelectric and ferromagnetic properties of x Ni0.8Zn0.2Fe2O4-(1-x) Pb0.99La0.02Zr0.65Ti0.35O3 composites

For the present study, two phase ceramic (ferroelectric-ferrite) composites using La substituted lead zirconate titanate (PLZT) and Ni-Zn ferrite (NZF) with compositional formula x Ni_0.8Zn_0.2Fe₂O₄-(1-x) Pb_0.99La_0.02Zr_0.65Ti_0.35O₃ (x?=?0, 0.05, 0.10 and 0.15) were synthesized by conventional solid state reaction route. From X-ray analysis, it was confirmed that no chemical reaction took place between individual phases. Dielectric properties were studied as a function of temperature and frequency. Decrease in dielectric constant and increase in dielectric loss was observed with increasing ferrite content. Anomalous behavior in paraelectric region was observed for all the composite samples (x?=?0.05, 0.10 and 0.15) at low frequencies. To study ferroelectric and ferromagnetic properties, P-E and M-H hysteresis loops were recorded respectively. Effect of electric field on magnetization was studied for all composite samples to confirm magnetoelectric coupling.     

Ni-Cu-Zn Ferrites for Low Temperature Firing: I. Ferrite Composition and its Effect on Sintering Behavior and Permeability

Ni-Cu-Zn ferrites of composition Ni_{1 − x − y}Cu_yZn_xFe₂O₄ with 0.4 ≰ x ≰ 0.6 and 0 ≰ y ≰ 0.25 were prepared by standard ceramic processing routes. The density of samples sintered at 900^∘C increases with copper concentration y. Dilatometry reveals a significant decrease of the temperature of maximum shrinkage with y. The permeability has maximum values of μ = 500–1000 for x = 0.6. The Curie temperature is sensitive to composition and changes form about 150^∘C for x = 0.6 to T_c > 250^∘C for x = 0.4, almost independent on the Cu-content. A small iron deficiency in Ni_0.20Cu_0.20Zn_{0.60 + z}Fe_{2 − z}O_{4 − (z/2)} with 0 ≰ z ≰ 0.06 significantly enhances the density of samples sintered at 900^∘C. The maximum shrinkage rate is shifted to T < 900^∘C. These compositions are therefore appropriate for application in low temperature co-firing processes. The permeability is reduced with z, hence a small z = 0.02 seems to be the optimum ferrite composition for high sintering activity and permeability.     

Spinel-structured Ni-free Zn0.9Cu x Mn2.1-x O4 (0.1 ≤ x ≤ 0.5) thermistors of negative temperature coefficient

Most spinel-structured materials of negative temperature coefficient (NTC) contain Ni, which have high cost. In this work, Ni-free Zn_0.9Cu _x Mn_2.1-x O₄ (0.1?≤?x?≤?0.5) NTC material system is developed. X-ray diffraction (XRD) spectra show that Zn_0.9Cu _x Mn_2.1-x O_\intered at 1100 °C crystallizes in a tetrahedral spinel structure, which is caused by the Jahn-Teller effect of the Mn³⁺ ions at the B sites. Cu2p_3/2 X-ray photoelectron spectra (XPS) demonstrate that most of Cu ions located at B sites are at the valance of 2+. The resistivity of Zn_0.9Cu _x Mn_2.1-x O₄ varies from 1,340 Ω cm to 51,489 Ω cm, and B value from 3,357 K to 4,276 K. The resistivity drift after annealing at 150 °C in air for 1,000 h is less than 3 % which is stable enough for practical application.     

A comparative study of high temperature properties of cobalt-free perovskites

Co-free perovskites with chemical composition Ba_0.5Sr_0.5Fe_0.8M_0.2O_3-δ (M = Ni, Cu, Zn) were synthesized by the modified Pechini method, and their structure and microstructure were characterized by XRD and SEM. Oxygen content, electrical resistivity and Thermal Expansion Coefficient (TEC) were evaluated in air between room temperature and 900 °C. The high-temperature properties of these perovskites were compared with those of Co containing Ba_0.5Sr_0.5Fe_0.8Co_0.2O_3-δ perovskite. The highest electrical conductivity was obtained for Ba_0.5Sr_0.5Fe_0.8Cu_0.2O_3-δ, with values of 47.6 Scm^?1 at 544 °C. This same composition also exhibits the highest oxygen vacancies concentration: 3-δ = 2.61 at room temperature. In contrast, the Ba_0.5Sr_0.5Fe_0.8Zn_0.2O_3-δ, showed lower electrical conductivity suggesting that the Zn⁺² ions block electron transport. Co-free perovskites seem to be stable at high temperatures for long term periods. However, these compounds suffered degradation at room temperature in samples stored in air.     

Structural and improved electrical properties of rare earth (Sm, Tb and Ho) doped BiFe0.975Mn0.025O3 thin films

Pure BiFeO₃ (BFO) and rare earth (RE) ion co-doped (Bi_0.9RE_0.1)(Fe_0.975Mn_0.025)O₃ (RE?=?Sm, Tb and Ho, denoted by BSFM, BTFM and BHFM) thin films were prepared on Pt(111)/Ti/SiO₂/Si(100) substrates by using a chemical solution deposition method. Formations of distorted rhombohedral perovskite structure for the thin films were confirmed by using an X-ray diffraction and a Raman scattering analysis. Microstructural features for the thin films were examined by using a scanning electron microscopic analysis. Among the thin films, the lowest leakage current density of 1.22?×?10^?6 A/cm² (at 100 kV/cm), large remnant polarization (2Pr) of 72.4 μC/cm² and low coercive field (2E _c ) of 689 kV/cm (at 980 kV/cm) were measured for the BTFM thin film.     

Effect of partial substitution of Mg for Co in Mn1.4Ni1.2Co0.4O4 NTC thermistors on electrical stability

Sintered Mn_1.4Ni_1.2Co_{0.4 − x} Mg_xO₄ samples were thermal constrained by heating at 850^∘C followed by air cooling. As-sintered and thermal constraint samples were composed of Mn- and Ni-rich phases with a cubic spinel structure. The substituted Mg suppressed the separation of Ni-rich phase in a Mn_1.4Ni_1.2Co_{0.4 − x} Mg_xO₄ solid solution and resulted in a more stable spinel structure. In particular, the substituted Mg led to a significant decrease in the resistance drift of the Mn_1.4Ni_1.2Co_{0.4 − x} Mg_xO₄ NTC thermistors after thermal constraint. This indicates that the Mg substituted Mn_1.4Ni_1.2Co_{0.4 − x} Mg_xO₄ NTC thermistors have good electrical stability in comparison with the Mg-free Mn_1.4Ni_1.2Co_0.4O₄ thermistors. We strongly recommended the substitution of Mg for Co in Mn-Ni-Co-O NTC thermistors for stabilizing their resistivity drift, i.e., ageing.     

Complex permittivity and permeability of Co-substituted NiCuZn ferrite at rf and microwave frequencies

NiCuZn ferrite has recently attracted a lot of attention for its application in high frequency (up to a few GHz) multilayer chip inductors (MLCIs) and for other microwave devices owing to their favorable electromagnetic properties and low densification temperature. In order to study the effect of substitution of cations by cobalt in small concentration on the dielectric and magnetic properties at low and high frequencies, bulk polycrystalline ferrite samples of starting composition (Ni_0.2Cu_0.2Zn_0.6)_{1 − x} Co _x Fe₂O₄, having x = 0, 0.01, 0.03 and 0.05, were prepared by citrate precursor method. Pure spinel (cubic) ferrite formation was confirmed by powder X-ray diffraction technique. Complex permittivity and permeability were measured at microwave frequencies (X-band) using the cavity perturbation method, which is a non-contact method. The values of real part of permittivity (ε ′) vary in the range 7–9.6 and of the imaginary part (ε ″) vary from 0.020–0.120, whereas real part of the permeability (μ′) lies in the range 2.6–14.0 and the imaginary part of permeability (μ″) varies from 0.5–6.0. It is observed that there is an increase in μ′ and decrease in the magnetic loss (tan δ _μ) on increasing the cobalt concentration from x = 0 to x = 0.05. The variation of these parameters, both with frequency in X-band and with the cobalt concentration, is discussed in this paper.     

Effect of transition metal substitution on elastoplastic properties of LiMn<Subscript>2</Subscript>O<Subscript>4</Subscript> spinel

LiMn₂O₄ (LMO) derivatives partially substituted with transition metals (e.g., Ni) have received attention for their higher energy density achieved at higher charge voltage than pure LMO, and may be attractive cathode candidates for emerging all solid state batteries. Accurate mechanical properties of these high voltage spinels are required for prediction of electrode and electrolyte fracture that may compromise battery lifetime and performance. Here, we quantified the Young’s elastic modulus E and hardness H for LMO, LiMn_1.5Ni_0.5O₄ (LMNO), and LiMn_1.5Ni_0.42Fe_0.08O₄ (LMNFO) spinel microparticles via instrumented grid nanoindentation. Elastic modulus E and hardness H increased by more than 40% (up to 145 and 11 GPa, respectively) as a result of Ni or Ni/Fe substitution; such substitution also reduces the lattice parameter and increases the oxidization state of Mn. These results demonstrate how changes in transition metal occupancy can significantly affect the mechanical properties of LMO spinel, and provide critical parameters for designing against fracture in all solid state batteries.     

PZN-PFW and PFN-PFW Relaxor Ferroelectric Ceramics by a Reaction-Sintering Process

Pb((Zn_1/3Nb_2/3)_0.6(Fe_2/3W_1/3)_0.4)O₃ and Pb((Fe_1/2Nb_1/2)_0.7(Fe_2/3W_1/3)_0.3)O₃ (PZNFW and PFNW) perovskite ceramics prepared by a reaction-sintering process were investigated. Without any calcination, the mixture of PbO, Zn(NO₃)₂, Fe(NO₃)₃, Nb₂O₅ and WO₃ for stoichiometric PZNFW and PFNW was pressed and sintered directly. Pyrochlore phase more than 25% were formed in PZNFW ceramics after 2 h sintering at 930–980C. PFNW ceramics of 100% perovskite phase were obtained after 4 h sintering at 930–1080C. A density of 8.13 g/cm³ (93.4% of theoretical value) was obtained after sintered at 1080C for 4 h. Dielectric constant at room temperature under 1 kHz reaches 32000 after sintered at 1080C for 4 h.