Raman and infrared spectroscopy of YBa2Cu3O7-delta-BaPbO3 composites

Abstract

pre present results of Raman and infrared spectroscopic studies of the composite system of superconducting YBa2Cu3O7-delta, and metallic BaPbO3, with the BaPbO3 fraction ranging from 5 to 30 in weight. The Raman spectra of the YBa2Cu3O7-delta grains in the composite system are typical of well-oxygenated YBa2Cu3O7-delta bulk single crystals, even up to the grain boundaries, independent of the BaPbO3 fraction. We have also performed infrared reflectivity measurements and have identified the major c-axis transverse-optical phonons of YBa2Cu3O7-delta, consistent with the single-crystal data, confirming that the constituent YBa2Cu3O7-delta crystallites are fully oxygenated. The absence of mode splitting suggests that the crystal symmetry of YBa2Cu3O7-delta grains remains the same as that of bulk single crystals. No phonons indicative of other YBa2Cu3O7- or BaPbO3-related impurity phases, such as YBa2Cu3O6, Y2BaCuO5, and Ba2PbO4, have been detected in our Raman and infrared spectra. All these optical features clearly indicate that YBa2Cu3O7-delta is well separated from BaPbO3 and that BaPbO3 is an excellent additive material for the synthesis of YBa2Cu3O7-delta bulk materials. (C) 1998 Elsevier Science B.V. All rights reserved.