Abstract
We investigated the infield superconducting properties of carbon nanotubes-Cu0.5Tl0.5Ba2Ca2Cu3O10−δ superconductor {(CNTs)x-(CuTl-1223)}; x = 0∼7 wt.% composites. The zero resistivity critical temperature {Tc(0)}, critical superconducting onset transition temperature {Tconset(K)} and glass transition temperature (Tg) have been shifted towards lower values after the addition of carbon nanotubes (CNTs). The double transitions for all concentration of CNTs have indicated the existence of vortex-glass phase. The significant resistive broadening {ΔT = Tconset(K)-Tc(0)} has been observed with increasing values of external applied magnetic field. The more increasing trend in resistive broadening has also been observed after the addition of CNTs in CuTl-1223 matrix. The magnetic field dependent activation energy Uo (H) has been calculated according to thermally activated flux flow (TAFF) model. The overall decreasing rate in pinning energy could be due to diffusion of carbon across the grain-boundaries.
Highlights
INTRODUCTIONThe value of vortex glass line can be calculated by critical field below which vortices can be pinned.[17,18] Normally, flux pinning strength has been calculated from activation energy and pinning force density
From application point of view Cu0.5Tl0.5Ba2Ca2Cu3O10−δ (CuTl-1223) superconducting phase of Cu0.5Tl0.5Ba2Can−1CunO2n+4−δ (n = 2, 3, 4 . . . ) homologous superconducting series is very promising for further investigation due to its higher superconducting parameters.[1,2,3] Different nanostructures have been added to enhance the superconducting properties of different cuprates.[4,5] Recently, number of research groups focused on nano-additive in bulk high temperature superconductors (HTSCs) to improve the inter-grains connectivity, superconducting volume fraction and flux pinning ability.[6]
Crystal structure and phase purity of (CNTs)x-(CuTl-1223) nanotubes-superconductor composites were determined by X-ray diffraction (XRD)
Summary
The value of vortex glass line can be calculated by critical field below which vortices can be pinned.[17,18] Normally, flux pinning strength has been calculated from activation energy and pinning force density. We have discussed the magnetic field dependent activation energy Uo (H) with the aim to understand the vortex-glass resistivity above Tg. We have explored the effects of CNTs addition on Uo (H) and other superconductor parameters. The ground material was put in quartz boats and placed in pre-heated chamber furnace at 860oC for 24 hours. The ground material was pressed under 3.8 tons/cm[2] pressure with the help of hydraulic press to make the circular shaped pellets These pellets were put into gold capsules for sintering at 860oC for 10 minutes and quenched at room temperature to get (CNTs)x-(CuTl-1223) nanotubes-superconductor composites
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