Temperature dependent impedance spectroscopy of (Co3O4)x/CuTl-1223 nanoparticles-superconductor composites

Abstract

Cobalt oxide (Co3O4) nanoparticles and Cu0.5Tl0.5Ba2Ca2Cu3O10-δ (CuTl-1223) superconducting phase were prepared by sol-gel and solid-state reaction methods, respectively. Co3O4 nanoparticles were added in CuTl-1223 superconducting matrix to get (Co3O4)x/CuTl-1223; x = 0–2.0wt% composites. Different experimental techniques like X-ray diffraction, dc-resistivity measurements and complex impedance spectroscopy were used for characterization of these composites. Crystal structure of CuTl-1223 superconducting phase remained unchanged after addition of Co3O4 nanoparticles, which suggested that these nanoparticles were settled at grain-boundaries. Superconducting transport properties were decreased after inclusion of Co3O4 nanoparticles. Role of Co3O4 nanoparticles addition at the grain-boundaries of the host CuTl-1223 phase was investigated and overall decreasing trend was observed in both real and imaginary part of impedance. The decrease in blocking factor by varying the content of Co3O4 nanoparticles is the evidence of increase in conductivity of grain-boundaries. The impedance master curves indicated the temperature independent dynamic process with non-Debye type relaxation phenomenon. The temperature dependent ac-conductivity with increasing contents of these Co3O4 nanoparticles was also investigated and increasing trend was observed.