A low-temperature and seedless method for producing hydrogen-free Si 3 N 4

A simple, seedless method for the synthesis of Si 3N4 from a hydrogen-free precursor system (Na 2SiF6(s)-N2(g)) was developed. From thermodynamic calculations and experimental results it is concluded that the gaseous chemical species SiF x (SiF4,SiF3, SiF2, SiF and Si) formed during the low-temperature dissociation of Na 2SiF6 in a conventional CVD system react in-situ with nitrogen to produce Si 3N4. Whiskers, fibers, coatings and powders were obtained via the Na 2SiF6-N2 system at pressures slightly above atmospheric pressure. Not only does the feasibility of the reactions for Na 2SiF6 dissociation and Si 3N4 formation increase with the temperature but also, once the SiF x