Infrared-Spectra Of The High-Tc Tlbacacuo Superconductors

The TlBaCaCuO superconductors with zero resistance at temperatures in the range of 100–123 K have been sintered by solid state reactions. Electron microscopy and X-ray diffraction studies reveal that they are multiphased, containing both Tl 2 Ba 2 CaCu 2 O 8 and Tl 2 Ba 2 Ca 2 Cu 3 O 10 superconducting phases. Infrared spectra have been measured at room temperature for the multiphase samples. The spectra display structures at ∼590 cm -1 ( P 1 ) and ∼530 cm -1 ( P 2 ) which seem characteristic to Cu-O stretching modes. The difference Δ P between P 1 and P 1 has been found to be related to the superconducting transition temperature. Smaller Δ P corresponds to a higher T c . The electron-like excitation of∼0.1 eV and the phonon-like structure at ∼850 cm -1 are also found to be important for high T c .