Effect of MgO Nano-oxide Additions on the Superconductivity and Dielectric Properties of Cu0.25Tl0.75Ba2Ca3Cu4O12-δ Superconducting Phase

The effect of MgO nano-oxide on both superconducting and dielectric properties of polycrystalline (Cu0.25Tl0.75)-1234 was studied. The MgO-content varied from x=0.0 up to 1.0 wt% of the sample's total mass. The volume fraction of the prepared samples (x=0.0, 0.2, 0.6 and 1.0 wt%) was estimated from the room-temperature X-ray powder diffraction patterns. The superconducting transition temperature T (c), calculated from resistivity data, increased from 122 to 136 K as x increased from 0.0 to 0.8 wt% and then it decreased to 117 K for x=1.0 wt%. Also, the dielectric properties of all samples were measured in the frequency range from 100 Hz to 4 MHz at different temperatures from 113 to 300 K. The real part of dielectric constant epsilon' was strongly dependent on both temperature and frequency for all x values. The imaginary part of dielectric constant epsilon aEuro(3) and loss factor tan delta showed dispersion which shift toward lower frequencies with decreasing temperature. The ac conductivity sigma (ac) was derived from the admittance and sample dimensions in the same frequency range. It followed the power law sigma (ac)(omega)similar to omega (-gamma) with gamma a parts per thousand 0.8.