Preparation of Ca-alpha-sialon ceramics with compositions along the Si3N4-1/2 Ca3N2 : 3AlN line

Starting from a powder mixture of alpha -Si3N4, AIN and Ca3N2, calcium alph a -sialon ceramics with extensive compositions on the line of Si3N4-1/2Ca(3 )N(2):3AlN (with a nominal composition of Cam/2Si12-mAlmN16) ranged from m = 0.5 up to m = 6.0 were hot pressed at 1700 degreesC for 1 h under 20 MPa. The sintering behavior of the sample was found to be significantly composi tion-dependent, and full densification was achieved for all compositions. T he solubility of Ca2+ in the present alpha -sialon was defined in the range of 0.5 less than or equal to x less than or equal to 1.7, which was wider than that in the Ca-alpha -sialon prepared from CaO. The single-phase sampl es revealed a similar microstructure comprising the matrix alpha -sialon gr ains and a grain boundary phase as the usual alpha -sialons. The energy dis persive X-ray spectroscopy analysis showed that 70-85 % Ca2+ ions entered t he alpha -sialon structure accompanying the Si substitution by Al.