Optimized Intergrain Connection and Transport Properties of Bi-2212 High-Temperature Superconductors by Ag Nanoparticles Inclusions

Abstract

Bi2Sr2CaCu2.0 O 8+δ (Bi-2212) polycrystalline bulks with Ag nanoparticles inclusion content of x = 0, 0.125, 0.250 and 0.500 wt% were fabricated by spark plasma sintering process. Bi-2212 precursor powders were synthesized by modified coprecipitation process Ag nanoparticles with the particle size of 5 ∼ 20 nm were synthesized by a microplasma reduction method. The influences of Ag inclusions on the textural structures and related superconducting properties were systematically investigated. Both XRD and XPS results revealed the elemental state of Ag in the bulks. Therefore, no doping effect was observed on the lattice parameters, as well as the critical temperature of Bi-2212 phase. Obvious enhancements of texture structures and increase of average grain size were obtained due to the change of crystallization behavior of Bi-2212 with Ag doping. Thus, intergrain connections were obviously improved, which contributed to the increase of self-field critical current density. Besides, the formation of better crystallized grain boundaries increased the number of effective pinning centers, thus enhanced the flux pinning properties and the in-field transport properties. Based on the influences mentioned above, improvement of critical current density of over 60 % was obtained with the optimal Ag content of 0.250 wt %.