Crystal growth of silicon nitride whiskers through a VLS mechanism using SiO2-Al2O3-Y2O3 oxides as liquid phase

Si3N4 whiskers were coated on Si3N4 whisker substrates through a VLS mechanism using SiO2-Al2O3-Y2O3 oxides as liquid phases. Alpha-Si3N4 whiskers having diameters of 0.4 to 0.7 mu m were used as seeds. After the seed whiskers were coated with SiO2-Al2O3-Y2O3 oxides, the oxide-coated whiskers were heated at 1490 degrees C N-2 including gas species generated by reacting amorphous Si3N4 and TiO2 powders. Resultantly, whisker-like products were newly formed on the seeds. The morphologies of the resulting whisker growth on the seeds resembled rose-twigs and centipedes with long legs. X-ray diffraction analysis indicated that the newly formed whiskers were beta-Si3N4. Droplets were observed on the tips of some whiskers. This suggested that the whisker growth proceeded through a vapour-solid-liquid (VLS) mechanism. (C) 1997 Elsevier Science Ltd and Techna S.r.l.