GROWTH, MORPHOLOGY AND SLIP SYSTEM OF ALPHA-SI3N4 SINGLE-CRYSTAL

Under the conditions of growth temperatures 1500 to 1700° C and total gas pressure 10 to 50 Torr, α-Si3N4 single crystals have been grown by chemical vapour deposition from a mixture of NH3, SiCl4 and H2. The crystals were transparent and brownish-red to colourless. The effects of the growth conditions on the crystal morphology, growth habit and growth direction have been investigated. On the basal and prismatic planes, the variation in Knoop hardness with orientation of the indenter long-axis has been measured at temperatures up to 1500° C; maximum hardness values were obtained along the 〈1 0 -1 0〉 direction for the basal plane and along the [0 0 0 1] directions for the prismatic planes. Hardness anisotropy analysis suggests that the active slip systems of α-Si3 N4 are {1 0 -1 0} [0 0 0 1] from room temperature to 1500° C. © 1979 Chapman and Hall Ltd.