Preparation of Ca-α-sialon Ceramics with Compositions along the Si3N4-1/2 Ca3N2:3AIN Line

Abstract Starting from a powder mixture of α-Si3N4, A1N and Ca3N2, calcium α-sialon ceramics with extensive compositions on the line of Si3N4 – l/2Ca3N2 : 3A1N (with a nominal composition of Ca m/2Si12 – m Al m N16) ranged from m = 0.5 up to m = 6.0 were hot pressed at 1700 °C for 1 h under 20 MPa. The sintering behavior of the sample was found to be significantly composition-dependent, and full densification was achieved for all compositions. The solubility of Ca2+ in the present α-sialon was defined in the range of 0.5 ≤ x ≤ 1.7, which was wider than that in the Ca-α-sialon prepared from CaO. The single-phase samples revealed a similar microstructure comprising the matrix α-sialon grains and a grain boundary phase as the usual α-sialons. The energy dispersive X-ray spectroscopy analysis showed that 70 – 85 % Ca2+ ions entered the α-sialon structure accompanying the Si substitution by Al.