Frequency-Dependent Electric Modulus Spectroscopy of (Co3O4)x/(CuTl)-1223 Nanoparticles–Superconductor Composites

Abstract

The (CuTl)0.5Ba2Ca2Cu3O10−δ {CuTl-1223} superconducting phase was synthesized by a well-established solid-state reaction route and the semiconducting antiferromagnetic cobalt oxide (Co3O4) nanoparticles were prepared by a chemical sol–gel method. The final (Co3O4)x/(CuTl)-1223; (x = 0–2.0 wt.%) nanoparticles–superconductor composites were obtained by adding Co3O4 nanoparticles in CuTl-1223 phase of the CuTl-based superconducting family. A temperature range of 77–298 K was chosen for frequency-dependent electric modulus spectroscopy measurements of (Co3O4)x/(CuTl)-1223 composites to interpret the dynamical aspects of electrical transport phenomena, such as ac-conductivity, carrier hopping rate, etc. The influence of grains as well as the grain boundaries on the ac-conduction properties was witnessed from the complex electric modulus spectra of these composite samples. The grain boundaries showed higher capacitance compared with the grains. This behavior of capacitance was decreased for grain boundaries and increased for grains with higher values of operating temperature in all the superconducting composite samples. The shifting of peaks towards a lower frequency regime in imaginary parts of the electric modulus spectra with increasing Co3O4 nanoparticle contents showed the presence of non-Debye-type relaxation within the material. The effects of these semiconducting antiferromagnetic Co3O4 nanoparticles on the ac-conduction mechanism of the host CuTl-1223 phase were studied, particularly in the perspective of the capacitive resistance contribution via electric modulus spectroscopy measurements.