High-pressure solid-state metathesis synthesis of ternary iron-based metal nitrides

Ternary ε-Fe_3-xM_xN_1+δ (M=Co,Ni) were synthesized as spherical bulk materials with variable components through composite high-pressure solid-state metathesis (HPSSM) reactions under 5 GPa and at 1673 K, employing diversity binary metal oxides (Fe₂O₃, CoO, NiO) and hBN as the reaction precursors. The structural characterizations of the as-prepared iron-based metal nitrides were determined by X-ray powder diffraction (XPD), field-emission scanning electronic microscopy (FE-SEM) and high-resolution transmission electron microscope (HRTEM), etc. First-principles calculations were used to explore the effect of pressure on the reaction enthalpy ΔH in HPSSM. Our results show that the high-pressure confinement environment is favorable for the synthesis of high-quality metal nitrides, and the HPSSM reaction is an effective synthetic route to the bulk iron-based metal nitrides.