Si3N4 Ceramics Systems

Phase diagrams of Si3N4-based ceramics systems which include two subsystems of Si3N4–MxXy and various SiAlON solid solutions are collected in this chapter. MxXy are oxides, rare earth oxides, or certain non-oxide compound usually as sintering aids of Si3N4 ceramic. At high temperature, MxXy react with Si3N4 forming diverse nitrogen-containing silicates and aluminosilicates reserved as secondary phase in these systems. Phase diagrams of SiAlON systems can be a guide for manufacturing of the SiAlONs ceramics. Five different types of SiAlON ceramics with significance in crystal chemistry and physical chemistry of nitrogen ceramics are presented in this chapter, namely, (a) β–SiAlON (β–Si3N4 ss), (b) α–SiAlON (α–Si3N4 ss), (c) O′SiAlON (Si2ON2–Al2O3 ss), (d) M′(R)–SiAlON (“Si3N4·R2O3”–Al2O3 ss), and (e) SiAlON polytypoids.