Si3N4-ZrO2-La2O3系统反应合成ZrN及相图构建

本工作研究了Si₃N₄-ZrO₂-La₂O₃三元系统的相关系, 采用X射线衍射仪分析了物相组成。结果表明, 在1500 ℃/1 h/N₂气氛条件下固相反应, 生成了ZrN和La_4.67Si₃O₁₃、La₅Si₃NO₁₂、La₄Si₂N₂O₇、LaSiNO₂、La₂Zr₂O₇等镧盐化合物的共存相。由于生成的氮化锆和硅酸镧等化合物不在Si₃N₄-ZrO₂-La₂O₃三元系统内, 需引入SiO₂测定SiO₂-La₂O₃-ZrO₂三元分系统相图, 进而扩大成Si₃N₄-ZrO₂-La₂O₃-SiO₂-ZrN五元系统, 本工作绘制并提出了此五元系统相图, 且提出了1570 ℃时SiO₂-La₂O₃-ZrO₂三元分系统实验相图。此外, 验证了La₂O₃在Si₃N₄-ZrO₂-La₂O₃三元系统反应中促进Si₃N₄-ZrO₂取代反应生成ZrN的作用。

Reaction Synthesizes of ZrN and Phase Diagram in the Si3N4-ZrO2-La2O3 System

Si₃N₄-ZrO₂-La₂O₃ ternary system were prepared via solid-state reaction at 1500 ℃ for 1 h with N₂ protection, yielding coexistence phase of ZrN and lanthanum-based compounds, such as La_4.67Si₃O₁₃, La₅Si₃NO₁₂, La₄Si₂N₂O₇, LaSiNO₂, and La₂Zr₂O₇. Since the generated ZrN and lanthanum-based compounds are not located on the triangle plane of Si₃N₄-ZrO₂-La₂O₃ system, it is necessary to add SiO₂ to extend the ternary into quinary system of Si₃N₄-SiO₂-La₂O₃-ZrO₂-ZrN. After the phase diagram of this quinary system is confirmed and presented, the phase diagram of La₂O₃-SiO₂-ZrO₂ ternary subsystem at 1570 ℃ is further proposed for the first time. In addition, La₂O₃ in the Si₃N₄-ZrO₂-La₂O₃ ternary system can help to simulate the substitution reaction between Si₃N₄ and ZrO₂ to produce ZrN.