Si doped Cu 0.5Tl 0.5Ba 2Ca 2Cu 3O 10− δ superconductors

Abstract

The Si doped (Cu 0.5Tl 0.5)Ba 2Ca 2Cu 3− y Si y O 10− δ ( y=0, 0.25, 0.5, 0.75, 1.0, 1.25) superconductor samples have been synthesized to investigate the effect of mobile carriers on the critical temperature and magnitude of diamagnetism of this family of cuprates. The Si doped samples have tetragonal structure as observed from the X-ray diffraction spectra. The c-axis length of the unit cell of (Cu 0.5Tl 0.5)Ba 2Ca 2Cu 3− y Si y O 10− δ was increased after the increase of Si concentration, whereas the critical temperature and the magnitude of diamagnetism have been decreased. The decrease in T c(0) and magnitude of diamagnetism is possibly due to the deficiency of carriers in CuO 2/SiO 2 planes caused by the +4 state of Si atoms. However, the post-annealing of these samples in oxygen atmosphere has increased the critical temperature and the magnitude of diamagnetism. The FTIR absorption measurements of (Cu 0.5Tl 0.5)Ba 2Ca 2Cu 3− y Si y O 10− δ samples have shown a softening of the apical oxygen mode of the type Cu(1)O ACu(2) and TlO ACu(2) with increased concentration of Si in the unit cell; the softening of this mode is directly linked with the increase in the c-axis lattice parameter of the (Cu 0.5Tl 0.5)Ba 2Ca 2Cu 3− y Si y O 10− δ superconductor.