DIELECTRIC PROPERTIES OF Bi1.6Pb0.4Sr2Ca2-xMgxCu3O10+δ (0≤ x ≤0.5) SUPERCONDUCTING SYSTEM
Samples of Mg-doped bismuth 2223 superconducting materials with nominal composition Bi1.6Pb0.4Sr2Ca2- xMgxCu3O10+δ (0≤ x ≤0.5) were synthesized by solid-state reaction method .The effect of magnesium on structural ,electrical resistivity and dielectric properties [dielectric constants (real and imaginary part ), dielectric loss factor (tan δ) and ac-conductivity (ζ ac) as a function of frequency ] has been investigated . XRD analysis showed the system has an orthorhombic structure with c/a ratio for Bi1.6Pb0.4 Sr2Ca1.8Mg0.2Cu3O10+δ system more than the other samples. A sharp drop of resistivity was observed for the same sample with a transition temperature equal to 104 K. The negative value of capacitance at lower frequencies for samples with x=0, 0.2, 0.5 has been observed in the dielectric measurements of these samples. This may attributed to difference in the Fermi levels of the contact electrodes with the superconductor ceramic sample.
Ghazala Y. Hermiz