Features of Nanostructured M_x−Pt_1−x (M = Fe, Co, Ni) Solid Solutions Obtained by Precursor Reduction in Aqua Solutions

It is shown that there was a preferential formation of nanocrystals of solid solutions M–Pt of face-centered cubic structure when co-reduction of metal precursors (M²⁺ (M = Fe, Co, Ni) and [PtCl₆]²⁻) by alkaline hydrazine hydrate solution was. It was demonstrated by methods of elemental analysis, X-ray diffraction, and high-resolution transmission electron microscopy. Content of Fe and Co in the phase of solid solutions was ≈ 11.5 ± 0.5 and ≈ 16.9 ± 1 at. %, respectively. By comparing the results of high-resolution transmission electron microscopy, elemental analysis, X-ray phase analysis, and X-ray structural analysis, it was established that in the Fe—Pt and Co—Pt systems, in addition to the M—Pt solid solutions with a face-centered cubic structure revealed by X-ray diffraction methods, nanodispersed metallic phases, practically inaccessible for registration, are formed in the regions above and below the limiting Fe and Co contents. However, as for nanostructured Ni—Pt system, there was not upper limit of Ni content in the solid solutions of face-centered cubic structure, up to 40 at. %. Therefore, the phase compositions were represented by two types of face-centered cubic structures, i.e. pure Ni phase and solid solution phases, with Ni content of 10–12 and 40 at. %. The key points about the nature of these structure-phase features reviewed in the article.