Reaction Synthesis 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 La4.67Si3O13, 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.