EFFECT OF ADDITIVE-OXIDE AMOUNT ON SINTERING OF SI3N4 WITH Y2O3 AND ND2O3

The effect of additive amount on the gas-pressure sintering of silicon nitride is investigated. Silicon nitride containing 0.5 to 10 mol% (SN10) of equimolar Y2O3-Nd2O3 is fired at 1600 to 1900-degrees-C for 4 h in 10 MPa N2 gas. A small amount of oxide (1 mol%; SN1) is effective for densification as well as a larger amount of oxide (6-10 mol%) when fired at 1900-degrees-C. Composition analysis of sintered specimens indicates that SN1 densifies through a small amount of SiO2-rich liquid-phase, whereas SN10 densifies by way of a large amount of additive-oxide-rich liquid phase.