DIRECT INVESTIGATION OF THE OXIDATION OF YBCO BY IN-SITU RAMAN-SPECTROSCOPY

The oxygen exchange process of a polycrystalline sample of YBCO has been experimentally studied, during a thermal cycle in controlled atmosphere, by means of Raman spectroscopy. The sample, initially at room temperature, was placed in a specially designed optical oven where it was thermally cycled under controlled atmosphere. During the cycles, the Raman spectra were recorded at regular intervals in order to monitor the oxygen exchange process. The spectra show quite interesting features in all the stages of the process, characterized by the progressive disappearance of the familiar phonon Raman bands and the progressive increase of new structures. In the present paper, we discuss how the evolution of the Raman spectra can be interpreted in terms of migration of the oxygen atoms in the sample.