Stability of Si ₃ N ₄ and Liquid Phase(s) During Sintering

Advanced sintering techniques for consolidation of Si 3 N 4 powders in the presence of an oxygen‐rich liquid phase(s) require high temperatures and usually high nitrogen pressures. A stability diagram is constructed for Si 3 N 4 as a function of the partial pressures of nitrogen (P N2 ) and silicon (P Si ). High P N2 (20 to 100 atm) increases the stability of Si 3 N 4 and the oxygen‐rich liquid phase by reducing the P Si and P Si0 , respectively. The region of high sinterability is outlined for submicrometer Si 3 N 4 powders containing 7 wt% BeSiN 2 and 7 wt% SiO 2 as densification aids .