RAMAN-SPECTROSCOPY OF (PB(1+X)/2CU(1-X)/2)SR2(Y1-XCAX)CU2O7+DELTA(X=0, 0.35)

Polarized Raman spectra of Pb(1+x)/2Cu(1-x)/2Sr2Y1-xCaxCu2O7+delta (x = 0, 0.35; delta almost-equal-to 0, 0.1) microcrystals have been obtained with various scattering configurations, allowing a distinction between Raman modes of different symmetry. Three A1g and the B1g modes, inherent to the ideal I4/mmm structure, have been unambiguously identified. Additional Raman modes, activated due to displacements of oxygen (O(3)) atoms from the (1c) sites in the Pb-O(3) planes have been observed. A strong dependence of the frequency versus oxygen and calcium contents has been observed for the A1g Raman active mode involving mainly vibrations of apex oxygen atoms (O(2)). The variations of the Raman spectra with x and delta are discussed.