Crystal Structure of 27R-SiAlON Synthesized Under Carbothermal Nitridation

ABSTRACT

Laboratory synthesized (carbothermal-reduction-nitridation) 27R-SiAlON is studied in terms of crystallographic and microscopic features by detailed X-ray diffraction and electron microscopy experiments. 27R- SiAlON is analyzed to possess rhombohedral R3m structure and is best represented as Si_1.1Al_7.9O_1.9N_8.1. Lattice parameters, ion positions, bond lengths, angles as well as the crystallite size and strain have been determined for the constituent phase. The R3m phase in hexagonal setting exhibits enormous anisotropy with pseudo-tetragonality ratio c/a√6 ∼10. The electron microscopy too offers evidence of preferential growth of platelike crystals of SiAlON due to its large c-axis.

GRAPHICAL ABSTRACT

Keywords:

• 27R-SiAlON
• Crystal structure
• Distortion
• Anisotropy