Study of the compression behavior and high-pressure strength of a-Si3N4 combining experimental and theoretical methods

The compression behavior and high-pressure strength of alpha silicon nitride (α-Si3N4) at pressures of up to 60 GPa are studied using synchrotron radiation powder diffraction, complemented with first-principles calculations. Compression experiments reveal that a-Si3N4 remains stable under the highest pressure and ambient temperature and has a bulk modulus of K0 = 256.3(±4) GPa, with a pressure derivative of K′0 = 5.6. However, the bulk modulus of experiment is higher than that of calculation (232.5 GPa). The correlation between strength and pressure is confirmed by diffraction peak broadening data. A transition from elastic deformation to plastic deformation of α-Si3N4 at 20 GPa is observed, indicating that α-Si3N4 begins to yield, with yield strength reaching 21 GPa at pressures of up to 20 GPa. A similar phenomenon is observed for MgO, WB3, and c-BC2N. Additionally, theoretical calculations are basically consistent with diffraction experimental results regarding structural stability and mechanical properties.