Compressive creep of silicon nitride with different secondary phase compositions

Compressive creep has been studied in several commercial and experimental grades of Si3N4, with similar microstructures but different grain boundary phase compositions. The experiments took place at 1400 and 1500 °C in static argon atmosphere. The creep rates at a given temperature showed more than one order of magnitude of grade to grade variability. However, all types of Si3N4 appear to deform by the same mechanism. When analyzed by a classic power-law equation for the creep parameters, n≈1 for all grades, while Q varied from 444 to 951 kJ mol−1. A solution-reprecipitation creep mechanism is considered compatible with these results.