Fe2O4 Ferrite Powders Research Articles

Magnetic and electrical transport properties of Cu0.5Ni0.5Fe2O4 ferrite synthesized by plasma arc discharge process

In this study, the plasma arc discharge process was employed to synthesize nanocrystalline Cu0.5Ni0.5Fe2O4 ferrite powders. A spinel-type ferrite structure has been formed successfully, exhibiting a saturation magnetization of 87 emu g−1 and a coercivity of 26 Oe. The investigation involved studying the frequency and temperature dependence of dielectric permittivity, dielectric loss, and DC/AC conductivity over a broad frequency range (1 kHz–1 MHz) in a temperature range of 298 K–403 K. The highest value of the dielectric contestant (4746) is observed at a frequency of 1 kHz and temperature of 313 K. A maximum in the DC conductivity is observed at 403 K, which can be ascribed to the combined effects of thermally activated hopping and an increase in the concentration of both n-type and p-type charge carriers at higher temperatures.

The effect of plasma arc discharge process parameters on the properties of nanocrystalline (Ni, Fe)Fe2O4 ferrite: Structural, magnetic, and dielectric studies

In this work, an attempt is made on optimization process parameters of the plasma arc discharge technique, including electrical current, atmosphere, and chamber pressure to synthesize nanocrystalline (Fe, Ni)Fe2O4 ferrite powders. The process was performed at the air and oxygen atmosphere with the applied arc current varying from 300 to 500 A and the chamber pressure of 1 and 2 atm. After establishing an arc between the electrodes, the as-synthesized powders were collected, and structure, magnetic, electromagnetic, and dielectric properties were examined in detail. The results show the highest value of the magnetic spinel phase (38.32 wt%) and saturation magnetization (35.1 emu/g) is obtained at the air atmosphere using an applied electrical current and chamber pressure of 400 A and 1 atm, respectively. The powders prepared in these processing conditions also exhibit the highest dielectric constant value over all the frequency ranges. Nevertheless, the powder synthesized at oxygen atmosphere in the applied electrical current of 400 A and chamber pressure of 1 atm shows the highest value of magnetic permeability over a wide range of frequency which is almost two times higher than that of the powders synthesized at the air atmosphere.

Microwave absorption properties of porous NiZn ferrite powders synthesized by solution combustion method: Effect of fuel contents

Hierarchical porous Ni0.5Zn0.5Fe2O4 ferrite powders were prepared by using metal nitrates as oxidants and glycine as fuel. The fuel contents were used for tuning the microstructure, magnetic, permittivity, and permeability properties to obtain a high microwave absorption performance. The pure NiZn ferrite powders were directly crystallized at lower fuel contents, while about 2 wt% intermetallic FeNi3 phase appeared at fuel to total metal nitrates molar ratio of 2. The combusted powders with high specific surface areas of 51 m2/g showed porous and foamy microstructure. The saturation magnetization of the combusted powders increased from 36.5 to 78.5 emu/g by the formation of FeNi3 phase at the higher fuel contents. With the increase of glycine fuel to total metal nitrates molar ratio from 1 to 2, the real and imaginary parts of permittivity increased from 4.5 to 6 and from 0.8 to 1.1, respectively, while the values of real and imaginary permeability slightly increased. The high microwave absorption performance, including reflection loss of −48 dB with effective bandwidth of 2.9 GHz in Ku band at the matching thickness of 4.5 mm, was obtained at the fuel to total metal nitrates ratio of 2.

The Use of Co-Precipitation to Produce Nano-Mn–Zn Ferrite ([MnxZn1−x]Fe2O4) from Waste Batteries

This study uses pure materials or waste batteries to produce a nanoscale Mn–Zn ferrite. Acid is used to dissolve the battery into solution and then co-precipitation is used to produce nanoscale ferrite. When the calcination temperature in an air atmosphere exceeds 600 °C, α-Fe2O3 is generated and there is a decrease in the saturated magnetization. Using waste batteries to produce [Mn0.54Zn0.46]Fe2O4 at a pH of 10, the saturated magnetization is 62.85 M (emu/g), which is optimal. At a pH of 10, the particulate diameter is largest, at about 40 nm. The stronger the crystal phase of Mn–Zn ferrite, the greater is the saturated magnetization. The ferrite crystal phase is analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM) and a vibrating sample magnetometer (VSM). The stronger the crystal phase, the larger is the average particulate diameter. The magnetic properties, the particulate diameter and the magnetic flux density of ferrite powders that are prepared under different conditions are studied. [MnxZn1−x]Fe2O4 ferrite powders can be used as an iron core and as resonance imaging materials.

Synthesis of nanocrystalline Mg0.6Cd0.4Fe2O4 ferrite by glycine-nitrate auto-combustion method and investigation of its microstructure and magnetic properties

Nanocrystalline Mg0.6Cd0.4Fe2O4 ferrite powders were produced by the glycine-nitrate auto-combustion method for the first time. The influence of the different molar ratios of glycine-to-nitrate G.N−1) on the characteristics of the prepared powders was systematically investigated by X-ray diffraction (XRD), inductively coupled plasma optical emission spectroscopy (ICP-OES), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), field-emission scanning electron microscopy (FE-SEM) and vibrating sample magnetometry (VSM). Thermodynamic calculations revealed that the adiabatic flame temperature changes from 598.79K to 1757.97K by increasing the G.N−1 ratios from 0.30 to 0.85. The results confirmed that under fuel-lean combustion (G.N−1 = 0.30), Mg0.6Cd0.4Fe2O4 nanoparticles can be obtained at a significantly lower temperature and shorter synthesis time, compared to other preparation methods like standard ceramic and co-precipitation. The XRD and ICP results showed that the crystallite size of the powders changes in the range of 8–43nm, and their Cd content notably decreases with increasing the G.N−1 values. The FE-SEM results proved that the porosity and size of the as-prepared ferrite nanoparticles drastically change with variations in the G.N−1 ratio. The evolution of phase, crystallite/particle size, and magnetic properties after annealing was discussed in detail. At the optimized annealing condition, the synthesized Mg0.6Cd0.4Fe2O4 ferrite offered a high saturation magnetization of 41.70Am2kg−1 and a coercivity of 1.92kAm−1, indicating noticeably better soft magnetic properties compared to the same ferrite produced by the other wet chemical methods.

Crystallographic and Magnetic Properties of Co, Zn, Ni-Zn Substituted Nano-size Manganese Ferrites Synthesized by Sol-gel Method

Cobalt-, zinc-, and nickel-zinc-substituted nano-size manganese ferrite powders, MnFe₂O₄, Mn 0.8 Co 0.2 Fe₂O₄, Mn 0.8 Zn 0.2 Fe₂O₄ and Mn 0.8 Ni 0.1 Zn 0.1 Fe₂O₄, were fabricated using a sol-gel method, and their crystallographic and magnetic properties were subsequently studied. The MnFe₂O₄ ferrite powder annealed at temperatures above 523 K exhibited a spinel structure, and the particle size increased as the annealing temperature increased. All ferrites annealed at 773 K showed a single spinel structure, and the lattice constants and particle size decreased with the substitution of Co, Zn, and Ni-Zn. The Mossbauer spectrum of the MnFe₂O₄ ferrite powder annealed at 523 K only showed a doublet due to its superparamagnetic phase, and the Mossbauer spectra of the MnFe₂O₄, Mn 0.8 Co 0.2 Fe₂O₄, and Mn 0.8 Zn 0.2 Fe₂O₄ ferrite powders annealed at 773 K could be fitted as the superposition of two Zeeman sextets due to the tetrahedral and octahedral sites of the Fe 3+ ions. However, the Mossbauer spectrum of the Mn 0.8 Ni 0.1 Zn 0.1 Fe₂O₄ ferrite powder annealed at 773 K consisted of two Zeeman sextets and one quadrupole doublet due to its ferrimagnetic and paramagnetic behavior. The area ratio of the Mossbauer spectra could be used to determine the cation distribution equation, and we also explained the variation in the Mossbauer parameters by using this cation distribution equation, the superexchange interaction and the particle size. Relative to pure MnFe₂O₄, the saturation magnetizations and coercivities were larger in Mn 0.8 Co 0.2 Fe₂O₄ and smaller in Mn 0.8 Zn 0.2 Fe₂O₄, and Mn 0.8 Ni 0.1 Zn 0.1 Fe₂O₄. These variations could be explained using the site distribution equations, particle sizes and magnetic moments of the substituted ions.

Effect of NaCl diluent content on phase, size and magnetic properties of Ni0.4Zn0.6Fe2O4 powders prepared by combustion synthesis

Ni0.4Zn0.6Fe2O4 ferrite powders were synthesized by Combustion synthesis (CS) with different NaCl diluent content. The powders were annealed at 1323K for 2h. Phases, size and magnetic properties of the powders with and without annealing were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectrometer (EDS) and vibrating sample magnetism (VSM). It shows that the impurity phases of the ferrite powders vanish after annealing, the size increases, and their shape becomes spherical and the distribution turns to narrower, but the saturation magnetization (Ms) of the annealed powders shows a maximum of 63.07emu/g when w is 6wt% in the reported data of ferrite prepared by other methods in literature. The powders size decreases with the NaCl content increasing. The maximum average size of the powders is 600nm and the minimum average size is 400nm.

Nickel Substitution Effects on Nano-sized Co, Mn and MnZn Ferrites Synthesized by Sol-gel Method

Nickel substituted nano-sized ferrite powders, Co 1-x Ni x Fe₂O₄, Mn 1-x Ni x Fe₂O₄ and Mn 1-2x Zn x Ni x Fe₂O₄ (0.0 ≤ x ≤ 0.2), were fabricated using a sol-gel method, and their crystallographic and magnetic properties were subsequently compared. The lattice constants decreased as quantity of nickel substitution increased, while the particle size decreased in Co 1-x Ni x Fe₂O₄ ferrite but increased for the Mn 1-x Ni x Fe₂O₄ and Mn 1-2x Zn x Ni x Fe₂O₄ ferrites. For the Co 1-x Ni x Fe₂O₄ and Mn 1-x Ni x Fe₂O₄ (0.0 ≤ x ≤ 0.2) ferrite powders, the Mossbauer spectra could be fitted as the superposition of two Zeeman sextets due to the tetrahedral and octahedral sites of the Fe 3+ ions. However, the Mossbauer spectrum of Mn 0.8 Zn 0.1 Ni 0.1 Fe₂O₄ consisted of two Zeeman sextets and one single quadrupole doublet due to the ferrimagnetic and paramagnetic behavior. The area ratio of the Mossbauer spectra could be used to determine the cation distribution equation, and we also explain the variation in the Mossbauer parameters by using this cation distribution equation, the superexchange interaction and the particle size. The saturation magnetization decreased in the Co 1-x Ni x Fe₂O₄ and Mn 1-2x Zn x Ni x Fe₂O₄ ferrites but increased in the Mn 1-x Ni x Fe₂O₄ ferrite with nickel substitution. The coercivity decreased in the Co 1-x Ni x Fe₂O₄ and Mn 1-2x Zn x Ni x Fe₂O₄ ferrites but increased in the Mn 1-x Ni x Fe₂O₄ ferrite with nickel substitution. These variations could thus be explained by using the site distribution equations, particle sizes and spin magnetic moments of the substituted ions.

Improved Magnetic Softness for NiCuZn Ferrite by Two-Step Sintering Method

The Ni0.2Cu0.3Zn0.5Fe2O4 ferrite powders with calcining temperatures Ta of 500°C, 600°C, 650°C, 700°C and 800°C were prepared by sol-gel auto-combustion method. The 650°C-calcined sample has the highest saturation magnetic induction Bs and initial permeability μi. Then the 650°C-calcined powder was made into bulk samples and sintered by the two-step sintering method. The samples were first heated to a higher temperature,TH = 1000 ~1100°C, then immediately cooled to a lower temperature,TL = 950°C, for isothermal sintering with a dwelling time of 2 h. It was found that the two-step sintering method could significantly enhance the μi of the bulk Ni0.2Cu0.3Zn0.5Fe2O4 samples, and keep an excellent temperature stability μi of in the range of 70 ~ 230°C. The ΔT(TH - TL) has a great influence on μi, and the larger ΔT is required for improving magnetic softness of the bulk samples.

Electrical and magnetic transport properties of Ni–Cu–Mg ferrite nanoparticles prepared by sol–gel method

Nanoscale Ni0.7−xMgxCu0.3Fe2O4 (0.0⩽x⩽0.5) ferrite powders were prepared by sol–gel method and obtained as dried gel after successful reaction between respective metal nitrates. X-ray diffraction (XRD) confirmed the successful synthesis of materials, and the formation of single-phase cubic spinel structure. The average particle sizes of these materials were found between 40 to 50nm and confirmed by TEM (±1). Dielectric constant (ε′) measured in the frequency range (42Hz to 5MHz) was found to decrease with increasing frequency of the applied field, which shows normal behavior, and has been explained in the light of Maxwell–Wagner interfacial polarization. Debye relaxation peaks were observed for lower concentration of Mg in frequency dependent dielectric loss tangent curves. Real and imaginary parts of impedance (Z′ and Z″) suggest existence of one relaxation mechanism which is attributed to the co-effect of grains and grain boundaries. The room temperature dc magnetization studies infer magnetic moment of Ni–Cu–Mg nanoparticles decreases with increasing Mg2+ doping content.

Preparation of nanocrystalline-coated carbon nanotube/Ni0.5Zn0.5Fe2O4 composite with excellent electromagnetic property as microwave absorber

A combined precipitation-hydrothermal method was used to fabricate carbon nanotube/Ni0.5Zn0.5Fe2O4 ferrite composite powders. The phase, microstructure and electromagnetic properties of CNT/Ni0.5Zn0.5Fe2O4 composites were investigated. After surface modification, The zeta potential value of CNTs could maintain at about −50 mV when pH is higher than 8, which affords a suitable surface environment for in situ coating of Ni0.5Zn0.5Fe2O4 nanocrystallines. With increasing CNTs content, the saturation magnetization of the composites is gradually reduced, while the complex magnetic permeability changes little. The complex dielectric constant of the composites is significantly increased when the concentration of CNTs approaches the percolation threshold value of 2 wt%. When CNTs content is 5 wt%, the reflection ratios are less than −10 dB within the frequency range 2–9 GHz, and the reflection ratios reach a minimum −32.5 dB at a frequency of about 3.9 GHz.

Synthesis and Characterization of Cu<sub>0.5</sub>Zn<sub>0.5</sub>Fe<sub>2</sub>O<sub>4</sub> Ferrite for Application as a Soft Magnetic Material

This work involved the synthesis and characterization of Cu0.5Zn0.5Fe2O4ferrite powders prepared by combustion reaction for use as soft magnetic materials. The powders were characterized by nitrogen adsorption (BET), XRD, Rietveld refinement, SEM, TEM and magnetic measures. The results indicate that the combustion reaction yielded crystalline powders containing spinel ferrite as the primary phase and traces of Fe2O3as secondary phase. The crystallite size and lattice microdeformation calculated from Rietveld refinements were 36 and 0.24 nm, respectively. The micrographic analysis revealed particles smaller than 100 nm and fine particle agglomerates. The particles were approximately spherical and their size, calculated by TEM, was 29 nm. The magnetic parameters indicated that the Cu-Zn ferrite powders presented closed hysteresis loops and soft magnetic properties.

Magnetic, Electric and Structural Properties of Ni Substituted Co-Zn Ferrite Nanoparticles Synthesized by Sol-Gel Method

Nickel substituted CoxZn0.8-x Fe2O4 (x=0.2,0.5 and 0.6) ferrite were synthesized by Sol-gel auto combustion method. The powders were sintering at 400 o c and 700 o c for 2hrs to densify properly. The samples were characterized by XRD, SEM and FTIR and Magnetic properties. The XRD used to analyze phase structure and lattice parameters. The FTIR spectra confirmed that synthesis material is ferrite. Morphology of ferrite powders were investigated by using SEM. Porosity of synthesis ferrite is measured. The saturation magnetization increases with increasing Co-Zn concentration. Resistivity of ferrite material is may be decreases due to vary concentration of Co and Zn. this paper we present a study of the magnetic and structural properties of Ni0.2CO0.2Zn0.6Fe2O4, Ni0.2CO0.5Zn0.3Fe2O4 and Ni0.2CO0.6Zn0.2Fe2O4 nanocomposites of different composition. The composition, crystal structure, morphology, and size distribution of Ni-Co-Zn ferrite nanocrystals can be controlled by adjusting the synthesis route and molar ratio of materials in the initial mixtures. The synthesized nano crystals have been characterized by XRD, SEM, FTIR, and Magnetic Properties presented below are the details of investigation. II. Experimental: The Ni0.2CO0.2Zn0.6Fe2O4, Ni0.2CO0.5Zn0.3Fe2O4 and Ni0.2CO0.6Zn0.2Fe2O4 ferrite powders were prepared by co-precipitation and hydro thermal technique using iron nitrate, zinc nitrate, cobalt nitrate, and nickel nitrate as reaction agent. To obtain Ni0.2CO0.2Zn0.6Fe2O4, Ni0.2CO0.5Zn0.3Fe2O4 and Ni0.2CO0.6Zn0.2Fe2O4 ferrite powders we have mixed AR grade iron nitrate, zinc nitrate, cobalt nitrate, and nickel nitrate with double distilled water. Citric acid was used as a chelating agent because it plays an important role in homogeneous mixture formation of metal cations. Reaction procedure was carried out in air atmosphere at room temperature. The composition was well shake and pH of solution is maintained as 7 by adding ammonia. The prepared solution was stirred on magnetic stirrer at low temperature 80 0 C to form a gel. The prepared ferrite samples were annealed for 400 0 C and 700 0

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Nanocrystalline Mg0.6Cd0.4Fe2O4 ferrite powders were produced by the glycine-nitrate auto-combustion method for the first time. The influence of the different molar ratios of glycine-to-nitrate G.N−1) on the characteristics of the prepared powders was systematically investigated by X-ray diffraction (XRD), inductively coupled plasma optical emission spectroscopy (ICP-OES), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), field-emission scanning electron microscopy (FE-SEM) and vibrating sample magnetometry (VSM). Thermodynamic calculations revealed that the adiabatic flame temperature changes from 598.79 K to 1757.97 K by increasing the G.N−1 ratios from 0.30 to 0.85. The results confirmed that under fuel-lean combustion (G.N−1 = 0.30), Mg0.6Cd0.4Fe2O4 nanoparticles can be obtained at a significantly lower temperature and shorter synthesis time, compared to other preparation methods like standard ceramic and co-precipitation. The XRD and ICP results showed that the crystallite size of the powders changes in the range of 8–43 nm, and their Cd content notably decreases with increasing the G.N−1 values. The FE-SEM results proved that the porosity and size of the as-prepared ferrite nanoparticles drastically change with variations in the G.N−1 ratio. The evolution of phase, crystallite/particle size, and magnetic properties after annealing was discussed in detail. At the optimized annealing condition, the synthesized Mg0.6Cd0.4Fe2O4 ferrite offered a high saturation magnetization of 41.70 Am2 kg−1 and a coercivity of 1.92 kA m−1, indicating noticeably better soft magnetic properties compared to the same ferrite produced by the other wet chemical methods.

Molten Salt Synthesis of Ni0.5Zn0.5Fe2O4 Powders

In this article, Ni0.5Zn0.5Fe2O4 ferrite powders were prepared by a reaction between Fe2O3, NiO, and ZnO powders in a molten salt. This article investigated the effects of firing temperature and holding time on the properties and microstructure of Ni-Zn ferrite powder via X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and thermal analysis. The synthesis mechanism is discussed. At 900°C, the grain contained pure spinel Ni0.5Zn0.5Fe2O4 and the grain size was smaller, so that Ni0.5Zn0.5Fe2O4 ferrite ceramic was easier to sinter. FESEM images illustrate that the average grain size increased as the sintereing temperature increased from 900 to 1050°C. The grain shapes changed from triangular patterns to cubic structures with the increase of temperature. The respective solubilities of NiO, ZnO, and Fe2O3 in flux controlled the synthesis mechanism.

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Nanocrystalline Mg0.6Cd0.4Fe2O4 ferrite powders were produced by the glycine-nitrate auto-combustion method for the first time. The influence of the different molar ratios of glycine-to-nitrate G.N−1) on the characteristics of the prepared powders was systematically investigated by X-ray diffraction (XRD), inductively coupled plasma optical emission spectroscopy (ICP-OES), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), field-emission scanning electron microscopy (FE-SEM) and vibrating sample magnetometry (VSM). Thermodynamic calculations revealed that the adiabatic flame temperature changes from 598.79 K to 1757.97 K by increasing the G.N−1 ratios from 0.30 to 0.85. The results confirmed that under fuel-lean combustion (G.N−1 = 0.30), Mg0.6Cd0.4Fe2O4 nanoparticles can be obtained at a significantly lower temperature and shorter synthesis time, compared to other preparation methods like standard ceramic and co-precipitation. The XRD and ICP results showed that the crystallite size of the powders changes in the range of 8–43 nm, and their Cd content notably decreases with increasing the G.N−1 values. The FE-SEM results proved that the porosity and size of the as-prepared ferrite nanoparticles drastically change with variations in the G.N−1 ratio. The evolution of phase, crystallite/particle size, and magnetic properties after annealing was discussed in detail. At the optimized annealing condition, the synthesized Mg0.6Cd0.4Fe2O4 ferrite offered a high saturation magnetization of 41.70 Am2 kg−1 and a coercivity of 1.92 kA m−1, indicating noticeably better soft magnetic properties compared to the same ferrite produced by the other wet chemical methods.

Electromagnetic Wave Absorption Behavior of NiZn-Ferrite Prepared via Hydrothermal Method

Ni0.5Zn0.5Fe2O4 ferrite powders were synthesized by a hydrothermal method. The nanoparticles of these materials were mixed with a thermal-plastic polyurethane (TPU)polymer in order to form a suitable composite for electromagnetic wave absorber in a frequency range from 2.0 to 15.0 GHz. The effect of particle size on the reflection loss was investigated by comparing nanosized and microsized powders. The reflection loss as a function of frequency ( f ), thickness of the absorber(d), the real and imaginary part of permittivity (ε’ /ε”) and the real and imaginary part of permeability (μ’/μ”) were obtained by calculation using the Bruggeman effective medium theory. The effect of Co2+, Cu2+, and Mg2+ on the reflection loss was also studied.

Self-propagating high temperature synthesis and magnetic properties of Ni0.35Zn0.65Fe2O4 powders

Ni-Zn ferrite powders were synthesized by self-propagating high temperature synthesis (SHS) method. X-ray diffraction, TEM and vibrating sample magnetometry (VSM) were used to characterize the phase composition, microstructure and magnetic properties of the combustion products. The effect of the combustion temperature (T c), the major parameter of the SHS process, on particle size, phase composition and magnetic properties of the products was also studied. The results showed that particle size grew with the increasing combustion temperature. The maximum saturation magnetization,M s, increased with combustion temperature indicating the growth of grain size and high degree of ferritization, while residual magnetization,M r, and coercive force,H c, decreased. Compared with other methods, Ni0.35Zn0.65Fe2O4 ferrite powders with improved magnetic properties can be obtained by SHS at 1000°C.

Magnetic properties of Zn2+ substituted ultrafine Co-ferrite grown by a sol-gel method

Ultrafine Co1−xZnxFe2O4 (0⩽x⩽1.0) particles are fabricated by a sol-gel method. The magnetic and structural properties of powders were investigated with x-ray diffraction, vibrating samples magnetometer and Mössbauer spectroscopy. The lattice parameter (a0) increases linearly with increasing Zn concentration (x) and follows Vegard’s law approximately. Co0.9Zn0.1Fe2O4 powders that were annealed at and above 673 K have only a single phase spinel structure and behave ferrimagnetically. Powders annealed at 523 K and 573 K have a typical spinel structure and are simultaneously paramagnetic and ferrimagnetic in nature. The magnetic behavior of Co0.9Zn0.1Fe2O4 powders annealed at and above 573 K shows that an increase of the annealing temperature yields a decrease of the coercivity and an increase of the saturation magnetization. The maximum coercivity and the saturation magnetization of Co0.9Zn0.1Fe2O4 ferrite powders are 1328 Oe and 81.1 emu/g, respectively. Mössbauer spectra of Co–Zn ferrite have been taken at various temperatures from 20 to 800 K. The isomer shifts indicate that the iron ions were ferric at the tetrahedral [A] and the octahedral [B]. The Néel temperature of Co0.9Zn0.1Fe2O4 was determined to be TN=790 K and It is found that Debye temperature for the A and B sites of the sample annealed at 1123 K is found to be ΘA=756±5 K and ΘB=199±5 K, respectively. The Néel temperature dramatically decreased with increasing x from about TN=870 K for x=0.0 to TN=35 K for x=1.0.

Self-propagating high temperature synthesis of Ni0.35Zn0.65Fe2O4 ferrite powders

The stoichiometric Ni0.35Zn0.65Fe2O4 ferrite powders were synthesized by SHS method. In the process of SHS, the effects of the molar ratio Fe/Fe2O3 in the starting mixture, oxygen pressure, grain size and relative density of the raw materials on combustion temperature, combustion wave velocity, phase composition and microstructure of the combustion products were investigated. X-ray diffraction, scanning electron microscope, TEM, vibrating sample magnetometry were used to characterize the microstructure and magnetic properties of the products. The results showed that as the molar ratio Fe/Fe2O3 increases, the combustion temperature and combustion wave velocity increased. The same results can be observed when the oxygen pressure increased from 0.1 to 0.9MPa. The increase of grain size and relative density of raw materials resulted in the decrease of combustion temperature and combustion wave velocity. Compared with other methods, SHS process leads to ferrite powders with improved magnetic properties.