Studies of the phonon modes and superconducting properties of Cu0.5Tl0.5Ba2Ca2Cu3-yZnyO10-δ (y = 0, 1.5, 2.5)

The phonon modes and superconducting properties of Cu0.5Tl0.5Ba2Ca2Cu3-yZnyO10-δ (y = 0, 1.5, 2.5) have been investigated. To optimize the carriers in the unit cell, annealing experiments were performed at different temperatures and for different annealing times. The resistivity and ac-susceptibility measurements revealed that the samples become optimally doped when they were annealed at 500 deg. C for 6 h. The optimum concentration of carriers in the conducting ZnO2/CuO2 planes gives the desired Fermi velocity VF that is necessary for enhanced superconductivity. The volume of the unit cell observed through x-ray diffraction scans is found to decrease with the increase of Zn doping, promoting an increase in the Fermi vector KF and effective density of states which results in enhanced superconductivity parameters. These annealing experiments manifested the importance of the apical oxygen modes of type Cu(1)-OA-M(2) and Tl-OA-M(2) and the CuO2 planar mode M(2)-Op-M(2) (where M = Zn/Cu) for superconductivity. The Fourier transform infrared (FTIR) absorption studies are consistent with the resistivity and ac-susceptibility measurements