Densification, Formation Behavior and Microstructure of (Ca,Mg) a Sialon

Ca,Mg) α Sialon for the compositions M xSi 3-x Al xO xN 16-x with x ranging from 0 3 to 1 4 were prepared by hot pressing technique The result showed that the crystalline phase in the sintered material consists of α Sialon and Mg containing AlN polytypoid when x is equal to or greater than 1 0 and the AlN polytypoid content increases as the x value increases By the use of duplex metal oxide CaO/MgO, instead of CaO, as additives to form α Sialon, the material possesses a better sintering ability TEM and EDAX results further revealed that the most of added Mg ++ can be incorporated into the Sialon to form magnesium AlN polytypoid phase, whereas the most added Ca ++ enters α Sialon structure The formation of magnesium containing AlN polytypoid phase in the composite materials can provide a new approach to reduce the amount of glassy phase at the grain boundary