Hot pressing of silicon nitride with ceria additions

Abstract

Hot pressing kinetics, $\text{α}\text{β}$ conversion reaction and β-phase texture were studied for (1 – 20) wt% CeO₂Si₃N₄ compositions hot pressed at T = 1823 ÷ 1973 K and P_a = 14.7 ÷ 39.2 MNm⁻¹ in a nitrogen atmosphere. Sintering is likely to occur in the presence of an intergranular cerium orthosilicate Ce_4.67(SiO₄)₃O liquid phase by a multicomponent mechanism including rheologic rearrangement, solution/reprecipitation and grain boundary sliding. The same solution/diffusion/reprecipitation mechanism seems to apply for densification and for the $\text{α}\text{β}$ conversion reaction in the early stages of hot pressing. An appreciable dependence of the β - phase texture on hot pressing parameters and amount of liquid phase is also featured.