Articles written in Bulletin of Materials Science

• Structural and magnetic properties of Co$_{1+y}$Sn$_y$Fe$_{2–2y–x}$Cr$_x$O4 ferrite system

The samples of the series Co$_{1+y}$Sn$_y$Fe$_{2–2y–x}$Cr$_x$O4 ferrites with 𝑥 = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5 and 𝑦 = 0.05, were prepared by the usual double sintering ceramic technique. The single-phase spinel structure of the samples was confirmed by using X-ray diffractometry technique. The lattice parameter 𝑎’ with an accuracy of ± 0.002 Å were determined using Bragg peaks of XRD pattern. The lattice parameter 𝑎’ decreases with concentration, 𝑥, which is due to the difference in the ionic radii of Cr3+ and Fe3+ ions. The X-ray intensity calculations were carried out in order to determine the possible cation distribution amongst tetrahedral (A) and octahedral [B] sites. The X-ray intensity calculations show Cr3+ ions occupying B site. The saturation magnetization, $\sigma_{s}$, and magneton number, $n_B$ (the saturation magnetization per formula unit), measured at 300 K determined from high field hysteresis loop technique decrease with increase in concentration, 𝑥, suggesting a decrease in ferrimagnetic behaviour. Thermal variation of low field a.c. susceptibility measurements from room temperature to about 800 K exhibits almost normal ferrimagnetic behaviour and the Curie temperature, $T_C$ determined from a.c. susceptibility data decreases with increase in 𝑥.

• Dielectric properties of Al-substituted Co ferrite nanoparticles

A series of polycrystalline spinel ferrites with composition, CoFe2–𝑥Al𝑥O4 (0 ≤ 𝑥 ≤ 1), have been synthesized by sol–gel method. The effect of Al-substitution on structural and dielectric properties is reported in this paper. X-ray diffraction analysis revealed the nanocrystalline nature in the prepared ferrite samples. The particle size, 𝐷, decreases with increase in Al-content. The lattice parameter, 𝑎 and X-ray density, 𝑑x, decreased with increase in Al-content. The dielectric properties for all the samples have been studied as a function of frequency in the range 100 Hz–10 MHz. Dielectric properties such as dielectric constant, 𝜀′, dielectric loss, 𝜀″ and dielectric loss tangent, tan 𝛿, have been studied for nanocrystalline ferrite samples as a function of frequency. The dielectric constant and dielectric loss obtained for the nanocrystalline ferrites proposed by this technique possess lower value than that of the ferrites prepared by other methods for the same composition. The low dielectric behaviour makes ferrite materials useful in high frequency applications.

• # Bulletin of Materials Science

Volume 45, 2022
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Continuous Article Publishing mode

• # Dr Shanti Swarup Bhatnagar for Science and Technology

Posted on October 12, 2020

Prof. Subi Jacob George — Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bengaluru
Chemical Sciences 2020