A sol-gel method was applied to prepare precursors for NdBa 2 Cu 3 O 7-x (Nd-123) and SmBa 2 Cu 3 O 7-x (Sm-123) superconducting compounds. The sintered products were examined by X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). The powders sintered at 950 and 1000 °C showed the formation of monophasic Nd-123 and Sm-123 superconductors. The formation of Nd-123 and Sm-123 phases from the sol-gel derived precursors at higher temperatures (1050 and 1100 °C), however, did not proceed due to the melting process. The correlation between the T C for different lanthanides (Ln -Ho, Nd and Sm) in the Ln-123 compound and orthorhombicity and oxygen stoichiometry were also estimated.
Structural changes in the Fe-Al system modified by high-energy ball milling were studied using Mössbauer spectroscopy and X-ray diffraction. Pure Fe and Al powders were mixed in compositions with 0.5, 1.5, and 5 at.% Fe and milled for various times using the Fritsch Pulverisette planetary mill. The formation of iron clusters was observed when the percentage of paramagnetic iron was higher than 0.5 at.%. It was found that the arrangement of Fe atoms in iron clusters is similar to that observed in FeAl n (n≥2) intermetallic compounds.
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