Equation of state of α-Si3N4s

Abstract

X-ray diffraction at high pressures reveals that α-${\mathrm{Si}}_3$ ${\mathrm{N}}_4$ is metastable to at least 48 GPa when compressed statically at 295 K, and yields a zero-pressure bulk modulus of ${\mathrm{K}}_0$=228.5 (±4) GPa, assuming a pressure derivative ${\mathrm{K}}_0^{|\mathrm{I}\mathrm{H}}$=4. The compression is nearly isotropic, but with the c direction being slightly more incompressible than the a direction, in good agreement with theory.