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

The solid state metathesis (SSM) reaction of CrCl sub 3 with Li sub 3 N in a sealed evacuated Pyrex ampoule at 445 deg C produces a propagation wave and enables phase pure Cr sub 2 N to be isolated. The SSM reaction of CrCl sub 2 and Mg sub 3 N sub 2 at 350-500 deg C with dilutant MgCl sub 2 under similar conditions produces single phase CrN. Reaction of chromium oxide with Li sub 3 N at 500 deg C produces CrN after 2 h and Cr sub 2 N 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.