RESONANT RAMAN-SCATTERING OF OXYGEN-DEFICIENT YBA2CU3O7-DELTA - EVIDENCE FOR THE COEXISTENCE OF ORTHO-I, ORTHO-II, AND TETRAGONAL MICROSTRUCTURES

The polarized Raman spectra of a single crystal of YBa2Cu3O7-delta (de lta approximately 0.6) at 15 K were studied using the 647.1, 568.2, 53 0.9, and 482.5-nm Kr+ laser lines. The results give clear evidence for a multiphase scattering volume with the main microstructure phases co rresponding to YBa2Cu3O7 (OI), YBa2Cu3O6.5 (OII), and YBa2Cu3O6 (T). S ignificant differences in the frequencies of the OI-, T-, and OII-rela ted modes, as well as variations of the mode intensities with HBARomeg a(L) and scattering geometry, result in apparent shifts of the Ba, Cu( 2), and O(4) lines.