THE EFFECTS OF CO SUBSTITUTIONS FOR CU IN YBA2CU3O6-SPECTRUM(X ON THEPHONON RAMAN)

We have investigated the phonon Raman spectra of YBa2Cu3-xCoxO7-delta ceramic samples prepared by both solid state reaction and a polymerize d complex method using Raman microprobe collection optics. With increa sing Co content the frequencies of the Ba, Cu(2), O(2)-O(3) and the ap ical oxygen O(4) c-axis vibrational modes change considerably. The cha nges are compared with changes of interatomic bond distances as obtain ed by neutron diffraction and indicate charge transfer effects between the CuO2 planes and the CuO chains with increasing Co substitution. T he CuO2 plane oxygen mode at 336 cm-1 exhibits slightly decreased coup ling to the electronic states with increasing Co content.