Raman and infrared spectroscopy of YBa 2Cu 3O 7−δ–BaPbO 3 composites

Abstract

We present results of Raman and infrared spectroscopic studies of the composite system of superconducting YBa 2Cu 3O 7−δ and metallic BaPbO 3, with the BaPbO 3 fraction ranging from 5 to 30 in weight. The Raman spectra of the YBa 2Cu 3O 7−δ grains in the composite system are typical of well-oxygenated YBa 2Cu 3O 7−δ bulk single crystals, even up to the grain boundaries, independent of the BaPbO 3 fraction. We have also performed infrared reflectivity measurements and have identified the major c-axis transverse-optical phonons of YBa 2Cu 3O 7−δ, consistent with the single-crystal data, confirming that the constituent YBa 2Cu 3O 7−δ crystallites are fully oxygenated. The absence of mode splitting suggests that the crystal symmetry of YBa 2Cu 3O 7−δ grains remains the same as that of bulk single crystals. No phonons indicative of other YBa 2Cu 3O 7- or BaPbO 3-related impurity phases, such as YBa 2Cu 3O 6, Y 2BaCuO 5, and Ba 2PbO 4, have been detected in our Raman and infrared spectra. All these optical features clearly indicate that YBa 2Cu 3O 7−δ is well separated from BaPbO 3 and that BaPbO 3 is an excellent additive material for the synthesis of YBa 2Cu 3O 7−δ bulk materials.