Infrared Absorption and CuO₅ Pyramid of High T_c Superconductor Bi-Sb-Sr-Ca-Cu-O System

The infrared absorption spectra of different superconducting phase of high Tc super conductor Bi-Sb-Sr-Ca-Cu-O have been measured . The results show that only in the range of 400cm-1 -700cm-1,there is a group of peaks which changes with different superconducting phases.According to group theory and infrared spectra of CuO, this group of peaks could be assigned to be the CuO6octahedron, the CuO5 pyramid and the CuO4plane quadrilateral,but not CU-O plane or CU-O chain. Furthermore, the quasi-three dimensional Cu-O layers consisting of CuO5 pyramids and proper coupling between them are essential factor for high Tc. It seems that the weaker compling of layers, the higher Tc