We have carried out a study of the effect of oxygen stoichiometry on the $k=0\mathrm{}$ phonon spectrum of the high-$T_c$ superconductor $\mathrm{Y}{\mathrm{Ba}}_2{\mathrm{Cu}}_3{\mathrm{O}}_x$ using Raman spectroscopy. Polycrystalline samples were prepared with oxygen content $x$ varying from 7.0, where the material is orthorhombic and superconducting, to 6.0, where it is tetragonal and semiconducting. The frequency and intensity of the $k=0\mathrm{}$ phonon modes of $A_g$ symmetry at 151, 340, 435, and 502 ${\mathrm{cm}}^{-1\mathrm{}}$ (for $x=7\mathrm{}$) were studied as a function of oxygen content.

• Received 26 February 1988

DOI:https://doi.org/10.1103/PhysRevB.38.284