Chromium nitrides (CrN, Cr2N) from solid state metathesis reactions:: effects of dilution and nitriding reagent

The solid state metathesis (SSM) reaction of CrCl3 with Li3N in a sealed evacuated Pyrex ampoule at 445 degrees C produces a propagation wave and enables phase pure Cr2N to be isolated. The SSM reaction of CrCl2 and Mg3N2 at 350-500 degrees C with dilutant MgCl2, under similar conditions produces single phase CrN. Reaction of chromium oxide with Li3N at 500 degrees C produces CrN after 2 h and Cr2N after 60 h. This is the first report of a metal nitride being formed in a SSM reaction using an oxide starting material. The SSM nitrides were shown to have superior bulk nitridation levels (combustion analysis) and equivalent microscopic compositions (EELS, XRD) to commercial materials. The phases of chromium nitride produced were correlated with reaction enthalpy, dilution conditions and nitriding agent. The products were analysed by X-ray powder diffraction, FTIR, combustion microelemental analysis, SEM/EDAX, XPS and ELNES.