Synthesis of a high-entropy orthoferrite containing 16-rare-earth elements via glycine-nitrate combustion and ammonium nitrate modification

Abstract

In this study, a high-entropy orthoferrite containing sixteen rare-earth elements, denoted as (RE)_1/16FeO₃, was prepared via glycine-nitrate solution combustion, followed by calcination at 800°C for 6 h. The effect of the fuel-to-oxidizer ratio (F/O) on phase formation and microstructural characteristics was investigated. The results revealed that all synthesised samples crystallised as a single-phase orthorhombic orthoferrite with the Pbnm space group. Among the investigated compositions, the sample prepared at F/O=2.0 exhibited the smallest crystallite size (~31 nm) and the highest BET specific surface area (~13.7 m²/g). Furthermore, the introduction of NH4NO3 into the combustion system reduced the crystallite size by approximately 30%, while increasing the specific surface area by about 50% and the total pore volume by nearly three times. These findings demonstrate that the proposed synthesis approach provides an effective route for tailoring the microstructure and surface properties of high-entropy orthoferrites, highlighting their potential for catalytic and energy-related applications.