Abstract

The room temperture first-order Raman spectra of the TI₂CaBa₂Cu₂O_x (2 CuO₂-layer) 2122 phase and the TI₂Ca₂Ba₂Cu₃O_x (3 CuO₂-layer) 2223 phase with respective superconducting transition temperatures of 100 and 125 K are presented. The weak Raman scattering efficiency of the essentially single 2122 phase and predominantly 2223 phase samples produces spectra with a considerable number of partially overlapping phonon peaks between 350 and 650 cm⁻¹ and a few at lower frequencies. Comparison with Raman spectra of the impurity phase candidates BaO₂, BaCuO₂, CaCuO₂, TI₂O₃, TICa₅Cu₆ allow identification of the intrinsic Raman modes of both superconducting phases. Factor group analysis of the tetragonal unit cells of both phases, space group 14/mmm, yields the mode classifications and the atoms involved in the modes of A_g symmetry which are expected to be the strongest. Similarities between the spectra of the 2223 and 2122 phases and comparison with the well-characterized YBa₂Cu₃O_x Raman spectrum suggest mode assignments for the high-frequency modes of A_g symmetry involving O motion.

© 1988 Optical Society of America