Synthesis of L10 alloy nanoparticles. Potential and versatility of the pre-ordered Precursor Reduction strategy

Abstract

A smart synthesis strategy exploiting the use of crystalline precursor salts, which until now has only been applied to the FePt system, was here extended to other binary alloys (CoPt, NiPt) with the aim of demonstrating the high potential of such a method and formulating a comprehensive explanation of the underlying process. Indeed, by exploiting the natural order of M(H2O)6PtCl6 (M = Fe, Co, Ni) crystalline precursor salts, consisting of M and Pt atoms on alternating planes that mimic the atomic arrangement of the L10 structure, highly ordered MPt alloy nanoparticles were obtained at lower processing temperatures and shorter reaction times than ordinary thermal processes, thus demonstrating the effectiveness and versatility of such an approach for the synthesis of L10 alloys. Comparing the results from the three different systems allowed a better comprehension of the underlying process, which involves the simultaneous occurring of the salt decomposition and the L10 ordering process. Indeed, differently to all the other existing approaches where thermal treatments are exploited to induce the disorder/order transition, the proposed strategy, which here we call Pre-ordered Precursor Reduction, is based on the opposite paradigm that is the preservation during the thermo-chemical treatment of the chemical order provided by the crystal. Thus, by properly choosing the starting salt, the proposed method can be used to synthesize a wide class of alloys, including those systems whose ordering formation is limited by kinetic and thermodynamic constraints.