C O Ehi-Eromosele
Articles written in Bulletin of Materials Science
Volume 38 Issue 5 September 2015 pp 1465-1472
Using nickel, zinc and ferric nitrates, and glycine in a fuel-rich composition, Ni1–𝑥Zn𝑥Fe2O4 nanoparticles were prepared by a simple low-temperature auto-combustion method without further sintering at high temperatures. The auto-combusted powders obtained were characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy, energy-dispersive X-ray (EDAX) analysis and vibrating scanning magnetometer measurements. XRD confirms the formation of pure nanocrystalline spinel phases with an average diameter of about 55 nm. Raman spectra show tetrahedral and octahedral sites in the structure of Ni1–𝑥Zn𝑥Fe2O4 and also imply the doping of Zn2+ and displacement of Fe3+ ions from the tetrahedral site. EDAX showed that the samples were close to the nominal compositions. The magnetic measurement shows that the saturation magnetization and remanence magnetization decreases with the increase in the zinc content.
Volume 38 Issue 7 December 2015 pp 1749-1755
The rapid solution combustion synthesis and characterization of sodium (Na)-substituted LaMnO3 phases at relatively low temperature using polyvinyl alcohol (PVA) as fuel were reported. The thermal decomposition process investigated by means of differential and thermal gravimetric analysis (TG–DTA) showed that the use of PVA as a fuel was satisfactory in the synthesis of the perovskite manganite compound. Structural study using X-ray diffraction showed that all the samples were single phasic without any detectable impurities within the measurement range. Also, the Na-substituted compounds crystallize with rhombohedral symmetry (space group R-3c, no. 167) with La0.80Na0.15MnO3 manganite sample giving the highest crystallinity. Microstructural features observed by field-emission scanning electron microscopy demonstrated that most of the grains were nearly spherical in shape with fairly uniform distribution and all the observed particles connect with each other. Energy-dispersive X-ray analyses confirm the homogeneity of the samples. Increase in magnetic moment was observed with the increase in sodium doping. Room-temperature vibrating sample magnetometer measurements showed that the samples were ferromagnetic with compositions 𝑦=0.10, 0.15 and 0.20 showing relatively high magnetic moments of 33, 34 and 36 emu 𝑔−1, respectively.
Volume 42 | Issue 6
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