RAMAN-STUDY OF THE 1222 COMPOUND (BI,CU)SR-2(R,CE)(2)CU2O9-DELTA (R=Y,HO)

Ceramics of nominal composition (Bi0.5Cu0.5)Sr-2(R(0.5)Ce(0.5))(2)CU2Ox (R = Y,Ho) were synthesized and characterized using XRD and SEM-EDX. The SEM-EDX analysis gives evidence for a large amount of(Bi,Cu1) vacancies, their number being dependent on the temperature of synthesis. From the polarized micro-Raman spectra all five A(1g) and two B-1g Raman modes expected for 1222 compounds were identified at 126-131, 167-169, 236-256, 465-469, and 573-583 cm(-1), and at 163-164 and 298-304 cm(-1), respectively. The Raman lines were assigned to definite atomic vibrations in close comparison with other compounds of similar structure. The frequencies of the B-1g-pair are explained by mixing of vibrations of oxygens in the Cu2-O and (R,Ce)-O layers. The effect of (Bi,Cu1) vacancies on some Raman frequencies and a possible multimode behaviour of the (R,Ce)-A(1g) line are also discussed.