Effect of Nano-Scale Additions on the Enhancement of Superconductivity in Y-Ba-Cu-O Materials

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The coherence length of Y-Ba-Cu-O superconductor is in the nano-meter range, therefore, nano-scale additions can be used to increase the number of effective pinning centers in top-seed melt-growth (TSMG) Y-Ba-Cu-O single grain materials. Different kinds of nano-scale additions: Y2O3, and Y2BaCuO5 (Y211) were mixed with precursor powders (YBa2Cu3O7 + Y2BaCuO) followed by TSMG process in air. SEM and TEM were used to investigate the size and morphology of the 211-particles as well as the distribution of defects (e.g. dislocations) in the matrix. It was found that the size of 211-particles was slightly reduced in nm Y2O3 doped samples, and sub-micro 211-particles were observed in nmY211 doped samples. In addition, the critical temperature, Tc, for all samples was similar and independent of the type of addition, while the enhancement of critical current density, Jc(H, T), varied with the types of nano-scale addition. Accordingly, the reactions between the superconductive matrix and different nano-scale additions resulted in different pinning properties. These samples with different nano-scale additions were studied using scaling rule analysis to differentiate their pinning mechanisms. For comparison, the results of SmBCO samples with nano-scale additions are also discussed in this study.

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