酸化タンタルの添加による Yb₂Si₂O₇ 粒界相を持つ Mo₅Si₃ 粒子強化 Si₃N₄ 複合材料の微構造への影響

抄録

Mo₅Si₃ particle reinforced Si₃N₄ composite with crystallized grain boundary phase of Yb₂Si₂O₇ was synthesized in-situ by sintering a green compact that contained Si₃N₄, MoO₃, Ta₂O₅, and Yb₂O₃ powders. The reaction between Si₃N₄, MoO₂, Ta₂O₅, and Yb₂O₃ at high temperature generated the Mo₅Si₃ particles, the complex molybdenum and tantalum silicide particles, and the grain boundary phase of Yb₂Si₂O₇ simultaneously. In the Mo₅Si₃-Yb₂Si₂O₇-Si₃N₄ composite, most of Mo₅Si₃ particles residing at the grain boundary phase, and had an average size of 0.18 μm. The addition of Ta₂O₅ promoted the formation of Mo₅Si₃ particle in Si₃N₄ grain and the generation of the Yb₂Si₂O₇ nano-particle in the grain boundary phase. The grain boundary phase and the Si₃N₄ grains were reinforced by the sub-micrometer sized Mo₅Si₃ particles and Yb₂Si₂O₇ nano-particles, which improved the strength of Si₃N₄. The crystallization of grain boundary phase was almost completed by adding the MoO₃, Ta₂O₅, and Yb₂O₃, while a small amount of amorphous phase and the thin amorphous films were detected from the grain boundary pockets, and the interfaces between the Si₃N₄, Yb₂Si₂O₇, and Mo₅Si₃, respectively.