Ceramics-Silikáty 47 (3) 88-93 (2003)

SYNTHESIS OF HIGH PURITY Si3N4 AND SiC POWDERS BY CVD METHOD

M. Halamka, Š. Kavecký, B. Dočekal, J. Madejová, P. Šajgalík

Fine, sub-micrometer, amorphous powders of SiC and Si₃N₄ have been prepared from SiH₄ - NH₃ and C₂H₂ - SiH₄ gaseous systems respectively, in tubular flow reactor. The Si₃N₄ powder prepared at 1373 K and NH₃/SiH₄ molar ratio of 11.5 is near stoichiometric in composition, isometric in morphology and the particle size is in range of 50 - 150 nm. The particle size of SiC powder prepared at 1373 K and SiH₄/C₂H₂ molar ratio of 2:1 was from the interval 10 to 100 nm. Recrystallization of these powders at 1853 K did not change substantially the particle size distribution and confirmed the Si₃N₄ and SiC as major compounds respectively. The content of metal impurities as Al, Cr, Cu and Fe in the presented powders is one order of magnitude lower compared to the commercially available powders prepared by other methods.

Keywords: Nanopowders, SiC, Si₃N₄, CVD, Metal impurities