Sintered silicon nitride having improved density and mechanical strength and process for producing the same.

摘要

High-density and high-strength sintered Si3N4 and a process for producing the same is disclosed. The sintered Si3N4 contains: 1 to 25 vol % of ZrO2; 0.5 to 15 wt % of at least one element selected from the group consisting of Y and the rare earth elements of the Lanthanide group; 1 to 15 wt % of at least one element selected from the group consisting of the elements of IVa (except Zr), Va and VIa groups of the Periodic Table; and the balance being Si3N4 consisting mainly of the beta phase and containing the ZrO2 and Y2O3 phase in the grain boundaries thereof. Such a sintered Si3N4 presents a high hardness together with a high fracture toughness is suitable for use not only as a cutting tool material but also as a high temperature structural member such as parts of the engine.