Raman Scattering in Single Crystal Ba2YCu3Oy

A Raman scattering study was performed in a variety of single crystals of both tetragonal and orthorhombic Ba2YCu3O y structures at room temperature. It is found that Raman spectra observed in the tetragonal crystal are much different from those in the orthorhombic one. Three modes with 500 cm-1 580 cm-1 and 637 cm-1 in energy in the orthorhombic crystal are tentatively assigned to be the copper-oxygen vibrational modes. The 500 cm-1 mode is assigned as the oxygen-stretching mode in Cu-O-Cu bond along the c-axis and its frequency is found to shift to 470 cm-1 in the tetragonal crystal.