Al Ferrite Research Articles

“Investigating impact of Ni-Cd substitution on structural magnetic and optical properties of nanosize Al ferrites”

Ferrites are among the most extensively studied materials, specifically due to their amazing and diverse characteristics. Therefore, we synthesized NixCd1-xAlyFe2-yO4 (NCAF) ferrites using a microwave auto-combustion process, with x varying from 0.0 to 1.0 and y set at 0.1. We conducted a meticulous characterization of their structural, surface morphological, magnetic, molecular vibrational and optical properties. X-ray diffraction confirms the lattice parameter and a single-phase spinel structure. Rietveld refined XRD patterns identified the Fd-3m space group cubic spinel phase. HR-TEM examination shows pseudo-spherical particles with an average size of 40–45 nm. Surface topography exhibits tiny, spherical microstructures. The lognormal histogram showed an average particle size of 56.6 nm–124.8 nm, decreasing with nickel concentration. At a nickel concentration (x) of 0.6, saturation magnetization (Ms) increases and then decreases at 1.0. FTIR confirms no organic phase and spinel development. Absorption measurements determined the band gap energy, which Tauc plot revealed to be 2.5870–2.1657 eV. We used the Kubelka-Munk function to find the band gap energy in the UV–Vis diffuse reflectance spectra (DRS), which was between 2.0027 and 1.6817 eV.

Nanoparticle synthesis and characterization of Li–Mg–Al ferrites: Potential applications in capacitor and magnetic storage media

Nanoparticle synthesis and characterization of Li–Mg–Al ferrites: Potential applications in capacitor and magnetic storage media

Creep in high Al ferrite based low density steel

Low density steels have attracted the attention of researchers across the globe as substitute alloys in structural and locomotive applications with promising mechanical properties and reduced density. Most of the research in low density steels is concentrated on room temperature properties after the thermomechanical processing of the same. In the present study, a high Al Fe-11Al-5Mn-0.1C low density steel was melted by vacuum arc melting in argon atmosphere. The as cast alloy was homogenized at 1200 °C and then hot rolled from 20 mm to 2 mm at 1100 °C. Hot rolled strips were annealed at 1000 °C for 1 h followed by furnace cooling. After thermomechanical processing, creep testing of alloy samples was carried out at 600 °C for 50 MPa and 100 MPa stress. The processed alloy has shown a total creep life of 6.21 h and minimum creep rate of 8.5 × 10 −1 h −1 for 100 MPa stress and for a stress of 50 MPa, creep life of 1005.1 h with minimum creep rate of 1.4 × 10 −3 h −1 . A dominating tertiary creep with appreciable secondary and negligible primary creep regime was observed. Fracture occurred due to cavitation at ferrite-kappa carbide interface. Ductile mode of fracture with fine dimples was observed.

Substitution effects on magnetic properties of Mg1.3-xMnxAlyFe1.8-yO4 ferrite

Mg1.3-xMnxAlyFe1.8-yO4 (x = 0.1–0.2, y = 0.15–0.3) spinel ferrites were prepared using conventional ceramic technique. Highly densified Mg–Mn–Al ferrites (with 99% theoretical density) were obtained, and the influence of Mn and Al substitution on the characteristics of these ferrites has been systematically studied. The microstructure, magnetic properties, and ferromagnetic resonance linewidth (ΔH) of the Mg–Mn–Al ferrites have been analyzed by X-ray diffraction, B-H analyzer, and ferromagnetic resonance (FMR) spectrometer. The results showed that all of the samples were single spinel phase. As Mn content increases and Al content decreases, both saturation magnetization (4πMs) and squareness ratio increase, while the coercivity (Hc) first increases and then decreases. In addition, good ferromagnetic resonance linewidth properties were also obtained as 143.8 Oe at 9.3 GHz for the sample with x = 0.17 and y = 0.20. The results imply that Mg1.3-xMnxAlyFe1.8-yO4 ferrites may be applicable for X-band (8–12 GHz) microwave devices.

Structural and magnetic properties of cadmium substituted Ni–Al ferrites

Nickel Cadmium Aluminum Ferrites with the general formula Ni1−xCdxAl0.6Fe1.4O4 where x=0, 0.25, 0.50 and 0.75 were prepared through standard double sintering reaction method. The crystallography, surface morphology and magnetic properties were studied by X-ray diffractometer (XRD), Scanning Electron Microscope (SEM) and Vibrating Sample Magnetometer (VSM), respectively. The expected single phase spinel structure was confirmed by XRD analysis. Lattice parameter and X-ray density were increased monotonically by increasing Cd concentration due to the larger ionic radii of the cadmium ion. Surface topography of the samples consists of fine cubical shape microstructures. The average grain size increased with increase in cadmium concentration. The saturation magnetization was found to be increased with increase in cadmium content up to x=0.50 and then decreased with further increasing cadmium concentration for x=0.75.

Electrical conduction in Ni–Al ferrites

The electrical resistivity of Ni–Al ferrite samples has been studied as a function of temperature. The completion of solid state reaction and the confirmation of single phase formation were confirmed by X-ray diffraction and therefore the lattice constant of the phases has been evaluated. The thermoelectric power measurement indicates that the samples are n- and p-type semiconductors and from dielectric studies, electrical conduction is interpreted in terms of polaron hopping model. To date, there is no paper that reported on the electrical properties of Al substituted Ni-ferrite.

Phase analysis study of copper ferrite aluminates by X-ray diffraction and Mössbauer spectroscopy

Abstract CuFe 2− x Al x O 4 (where x =0.0–0.6) have been synthesized at 950°C, 1000°C, 1050°C and 1100°C using the usual ceramic method. The Mossbauer measurements show reasonable values of magnetic as well as electric hyperfine interactions. At higher sintering temperatures, the spinel ferrite phase is partially dissociated forming delafossite phase in addition to the main matrix. The delafossite phase manifested itself as paramagnetic doublet overlapping the main Mossbauer spectra measured at room temperature. Furthermore, X-ray diffraction studies confirmed the presence of the CuFeO 2 (delafossite) phase of Cu–Al ferrite.

Mössbauer and Neutron Diffraction Studies on Co–Al Ferrite

Mössbauer and Neutron Diffraction Studies on Co–Al Ferrite

On the instability threshold of cobalt substituted Ni–Al ferrite at high-microwave-power levels

Parallel-pump spin-wave instability in polycrystalline Ni–Al ferrite has been measured at 9.384 GHz. The ground degeneracy of Co 2+ ions with concentration between 0.01 and 0.025 ions/f.u. added stoichiometrically, gives minimum losses and high-instability threshold values. Generalized instability theory for oblique pumping is used to reproduce the experimental butterfly curves. Results show a strong dependence of spin-wave linewidth on wave vector and crystalline anisotropy of cobalt.

Effect of Cu substitution on conductivity of Ni–Al ferrite

Electrical properties of Cu substituted Ni–Al ferrite Ni 1− x Cu x Al y Fe 2− y O 4, with (0.0< x<1.0 and y=1.0) are investigated by a.c. conductivity measurements in the frequency range (10 2–10 5 Hz) and over the temperature range (300–600 K). The obtained results of these materials reveal a semiconducting behavior at low concentration of Cu. A semiconducting-to-metallic transition has been observed with increasing Cu content in these compounds. All studied compositions exhibit a transition with change in the slope of conductivity versus temperature curve. This transition temperature is found to decrease linearly with increasing Cu concentration x. The results of conductivity measurements are explained in the light of the cation–anion–cation and cation–cation interactions at the octahedral B-sites.

Oxidative dehydrogenation of 1-butene over ZnAl ferrites

The aluminum introduction into the zinc ferrite ZnFe 2− x Al x O 4 in the range 0.0 ≤ x ≤ 1.0 was studied. These ferrites were calcined at two temperatures, 550°C and 750°C. X-ray diffraction (XRD) patterns showed that they have a spinel structure with Al 3+ replacing Fe 3+ in octahedral sites. The crystallite size decreased as the aluminum introduction increased. At high calcination temperature, sintering and segregation processes occur. Linear correlations were found between XRD and Mössbauer parameters. Mössbauer spectra showed that the symmetry of the electron distribution decreased around the nucleus of Fe 3+, as the aluminum content increased. Such asymmetrical distribution of the electron density may be associated to the spatial accommodation of aluminum in the neighboring octahedral sites. Oxygen atoms turn out to be more basic due to the charge transfer from Fe 3+ to O 2− in the FeO bond. Hence the acid-base type dissociation of the CH bond for the n-butenes activation is favored. The highest yield of butadiene was obtained for the samples treated at 750°C whereas for the samples calcined at 550°C, double bond isomerization of 1-butene occurs in competition with the oxidative dehydrogenation.

Resistivity and thermoelectric power of Ni—Al ferrites

The thermoelectronic power (α) of the system NiAlxFe2−xO4 and dc electrical resistivity (ϱ) are studied as a function of temperature and composition (x = 0, 0.2, 0.4, 0.6, 0.8, and 1). The single phase spinel structure is verified by X-ray analysis. The conductivity in these compounds is explained in the light of the hopping mechanism. The results show that the resistivity increases with increasing aluminium content and the activation energy of conductivity in the paramagnetic region is higher than that in the ferrimagnetic region. The transition temperature (Tc) shifts to lower temperatures with increasing aluminium content. The thermoelectric power measurements indicated that the conductivity is due to compensation of electrons and holes. The majority of carriers are holes when the Al3+ replaces 50% of Fe3+ in the samples. The drift mobility μn for electrons is calculated at different temperatures. It increases exponentially with temperature as expected in case of ferrites and the values ranged between 10−4 and 10−6 cm2/Vs at room temperature. Die Thermospannung (α) des Systems NiAlxFe2−xO4 und der elektrische Gleichstromwiderstand (ϱ) werden in Abhangigkeit von Temperatur und Zusammensetzung (x = 0; 0,2; 0,4; 0,6; 0,8 und 1) untersucht. Die einphasige Spinelstruktur wird durch Rontgenanalyse bestatigt. Die Leitfahigkeit in diesen Verbindungen wird mit dem Hoppingmechanismus erklart. Die Ergebnisse zeigen, das der Widerstand mit wachsendem Aluminiumgehalt ansteigt und das die Aktivierungsenergie der Leitfahigkeit im paramagnetischen Bereich hoher ist als im ferrimagnetischen Bereich. Die ubergangstemperatur (Tc) verschiebt sich mit wachsendem Aluminiumgehalt zu niedrigeren Temperaturen. Die Thermospannungsmessungen zeigen, das die Leitfahigkeit durch Kompensation von Elektronen und Lochern hervorgerufen wird. Die Mehrheit der Trager sind Locher, wenn Al3+ 50% des Fe3+ in den Proben ersetzt. Die Driftbeweglichkeit μn fur Elektronen wird fur verschiedene Temperaturen berechnet. Sie nimmt exponentiell mit der Temperature zu, wie im Fall der Ferrite erwartet, und die Werte liegen zwischen 10−4 und 10−6 cm2/Vs bei Zimmertemperatur.

Complex susceptibility of high-resistivity ferrites

A new method of presentation of the variation with frequency of the complex susceptibility of ferrites brings out clearly its behaviour at high frequencies. This method is applied to results of measurements made at very close frequency intervals on Mg–Al and Ni–Zn ferrites. The susceptibility of some of these ferrites presents several anomalies which appear on the curves as sinuosities or loops. The possible causes of these anomalies are discussed with the help of a comparison of results obtained on the same samples with and without superimposed d.c. magnetic fields. The influence of Al2O3 content on permeability and losses of Mg–Al ferrites is also examined.