A low-temperature and seedless method for producing hydrogen-free Si3N4
A simple, seedless method for the synthesis of Si3N4 from a hydrogen-free precursor system (Na2SiF6(s)-N2(g)) was developed. From thermodynamic calculations and experimental results it is concluded that the gaseous chemical species SiFx (SiF4,SiF3, SiF2, SiF and Si) formed during the low-temperature dissociation of Na2SiF6 in a conventional CVD system react in-situ with nitrogen to produce Si3N4. Whiskers, fibers, coatings and powders were obtained via the Na2SiF6-N2 system at pressures slightly above atmospheric pressure. Not only does the feasibility of the reactions for Na2SiF6 dissociation and Si3N4 formation increase with the temperature but also, once the SiFx chemical species are formed by the former, the latter reaction is even more viable. Amorphous Si3N4 is obtained at temperatures of up to 1173 K while crystalline α- and β-Si3N4 are formed in the range 1273-1573 K and with processing times as short as 120 minutes. Optimal conditions for maximizing Si3N4formation were determined.
| Main Authors: | , , |
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| Format: | Digital revista |
| Language: | English |
| Published: |
Sociedad Mexicana de Física
2008
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| Online Access: | http://www.scielo.org.mx/scielo.php?script=sci_arttext&pid=S0035-001X2008000300005 |
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