Problems and prospects of Si3N4 materials for applications at temperatures above 1400 deg C

Based on the understanding of the limiting mechanisms during service in structural applications at elevated temperatures, the potential of silicon nitride materials up to temperatures of 1500 deg C is discussed. It is possible to improve the mechanical properties significantly by microstructural tailoring of the Si3N4-material. The three examples described in this study, which are the optimization of the grain boundary phase composition, the tailoring of microstructure and grain boundary in Si3N4-SiC-nanocomposites and the influence of the silicide addition in Si3N4-MoSi2-composites, will give an impression about beneficial microstructural effects suitable to improve the high temperature properties of Si3N4-materials like creep, subcritical crack growth or oxidation resistance.