RAMAN AND INFRARED-SPECTROSCOPY OF YBA2CU3O7-DELTA-BAPBO3 COMPOSITES

pre present results of Raman and infrared spectroscopic studies of the composite system of superconducting YBa2Cu3O7-delta, and metallic BaP bO3, with the BaPbO3 fraction ranging from 5 to 30 in weight. The Rama n spectra of the YBa2Cu3O7-delta grains in the composite system are ty pical 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, consis tent with the single-crystal data, confirming that the constituent YBa 2Cu3O7-delta crystallites are fully oxygenated. The absence of mode sp litting suggests that the crystal symmetry of YBa2Cu3O7-delta grains r emains the same as that of bulk single crystals. No phonons indicative of other YBa2Cu3O7- or BaPbO3-related impurity phases, such as YBa2Cu 3O6, Y2BaCuO5, and Ba2PbO4, have been detected in our Raman and infrar ed spectra. All these optical features clearly indicate that YBa2Cu3O7 -delta is well separated from BaPbO3 and that BaPbO3 is an excellent a dditive material for the synthesis of YBa2Cu3O7-delta bulk materials. (C) 1998 Elsevier Science B.V. All rights reserved.