Thermally activated dissipation and pinning mechanisms in a Bi2223 superconductor with the addition of nanosized ZrO2 particles

The experimental results of the effect of low magnetic field and temperature on the transport proprieties of bulk Bi2223 with added ZrO2 nanoparticles (10-20 nm) are presented. The mechanisms responsible for the broadening of the resistive transition under magnetic field are discussed. The resistivity ρ(T) dependences are well described by the Ambegaokar-Halperin (AH) model. The AH parameter C(H) has been used to estimate the critical current density Jcj(0) at zero temperature in the grain boundaries. The critical current Jcj(0) in the grain boundaries decreases as a power law, Hn, which is an indication of the sensitivity of a single junction between the superconducting grains to the applied magnetic field. The magnetic field and the temperature dependences of the critical current have been studied with a central objective to determine the dominant source and mechanism of vortex pinning in the added sample. Nevertheless, in the low-field regime it can be viewed as a single vortex pinning mechanism followed by a transition to collective pinning in the high-field region. Two contributions to the critical current density have been identified and quantified: the weak pinning and the correlated disorder. We demonstrate in the present work that the correlated disorder coming from Bi2223/Zr-nanophase interfaces is dominant in the high temperature range (T ≥ 40 K), and the weak pinning centres associated to the defects generated by Zr-naophases embedded in matrix superconducting Bi2223 are dominant in the low temperature region (T ≤ 30 K).