Abstract
We investigated the chemical reactivity and percolation characteristics of insulating nanocrystalline YBa2ZrO5.5 prepared by modified combustion route and the YBa2Cu3O7−δ superconductor composite system. Structural analysis was done by using X-ray diffraction technique, surface morphology of the samples was studied using scanning electron microscopy, and electrical transport measurements like critical transition temperatures (Tc) and self-field transport critical current (Jc) were done by using standard four-probe technique. It is found that, in YBa2Cu3O7−δ-nano-YBa2ZrO5.5 composite system, the superconductor and insulator materials coexist as separate phases without any noticeable chemical reaction even after sintering at high temperatures. Furthermore, percolation threshold and critical exponent are found to be VC=0.3, t=1.68, and u=2.7. And the analysis of the current flow in the polycrystalline samples reveals weak link behavior in the majority of grain connections.
Highlights
High temperature superconductors with transition temperatures above 77 K in ceramic materials have received tremendous responsiveness because of their scientific and practical potential
This is indicative of the polycrystalline nature of the crystallites, but the spotty nature of the selected area electron diffraction (SAED) pattern could be due to the fact that finer crystallites with related orientations were agglomerated together, resulting in a limited set of orientations
In this paper we have studied the chemical reactivity and percolation behavior using electric transport measurements in polycrystalline YBa2Cu3O7−δ superconductornano-YBa2ZrO5.5 composite
Summary
High temperature superconductors with transition temperatures above 77 K in ceramic materials have received tremendous responsiveness because of their scientific and practical potential. It will be significant to study the percolation and superconductivity of composites involving superconductor inserted in an insulator medium. Granular nature along with short coherence length [4] and large penetration depth [5] of high temperature superconductors allows us to investigate the percolation behavior, fractal properties, quantum size effects, thermal fluctuations, and size effects on superconductivity. A high Tc superconductor-insulator system is very difficult to obtain without compromising the superconducting properties. The chemical nonreactivity of the substrate materials with superconductors indicates their potential as substrates for film deposition. The chemical compatibility of materials with the superconductor at the processing temperature is crucial. Superconductor-insulator percolation studies are a medium to understand the fundamental mechanism behind high temperature superconductivity
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