Stress dependence of the raman spectrum of β-silicon nitride

The stress dependence of the Raman bands of β-silicon nitride, β-Si3N4, has been investigated. In the stress range examined (from -200 to +200 MPa), low-frequency shift bands (namely the 183, 205, and 226 cm-1 lines) do not show any frequency change with the stress, whereas the highfrequency shift bands (862, 925, and 936 cm-1) have been found to have a linear stress dependence. The pertinent piezo-spectroscopic coefficients have been determined and are found to depend strongly on the additives used to promote densification presumably being taken into solid solution into the β-Si3N4 phase.