Microwave sintering of Si3N4 with LiYO2 and ZrO2 as sintering additives

✍ Scribed by Sreekumar Chockalingam; David A. Earl

• Publisher: Elsevier Science
• Year: 2010
• Weight: 333 KB
• Volume: 31
• Category: Article
• ISSN: 0261-3069
• DOI: 10.1016/j.matdes.2009.09.053

✦ Synopsis

Phase transformation, microstructure development and mechanical properties of 2.45 GHz microwavesintered silicon nitride (Si 3 N 4 ) with lithium yttrium oxide (LiYO 2 ) and zirconia (ZrO 2 ) sintering additives were investigated. It was found that a to b phase transformation completed at a lower temperature of 1500 °C. Scanning electron microscopy (SEM) micrographs revealed a bimodal microstructure with a large number of elongated b-Si 3 N 4 grains in addition to smaller grains. Surface residual porosity was observed in all sintered samples due to selective localized over heating of grain-boundary glassy phase. The high aspect-ratio of b-Si 3 N 4 grains exhibited significant crack deflection, debonding and pull-out. It was observed that Vickers hardness and indentation fracture toughness increased with increasing sintering temperature.