Raman spectra of YBa2Cu3Ox (x=6-7)

Raman spectra of polycrystalline YBa2Cu3Ox with various oxygen content x were recorded at 30 K. The intensity of a peak at 505 cm-1 depends on the oxygen content very strongly. This peak becomes weak as the oxygen content decreases and finally disappears at x=6.05. The last result disagrees with previous Raman studies on the tetragonal phase. Other spectral changes, disappearance of the 115 cm-1 peak and shifts of some peaks, are observed at the oxygen content of about 6.8. These spectral changes may be related to a phase change from the so-called Ortho-I phase to the Ortho-II phase. The dependence on the excitation wavelength was also examined