Abstract
A Yb2O3-SiO2 doped silicon nitride ceramic, prepared such that the composition was placed directly on the Yb4Si2O7N2-Si3N4 tie line, was hot pressed sintered. The compressive creep behaviour of the sintered Yb4Si2O7N2-Si3N4 material was examined at 1400, 1450 and 1500°C under a stress range of 250-400 MPa in a nitorgen atmosphere. The sintered material exhibited high resistance to creep. The stress exponents were found to be ~1.9 at 1400°C, ~2.1 at 1450°C and ~2.1 at 1500°C. The activation energy obtained was 510 ± 25 kJ mol-1. The values of the stress exponents and the activation energy suggest a cavitational process, accommodated by grain boundary sliding, viscous flow and solution-reprecipitation, as the most probable dominant creep mechanism.