(Y0.6Ca0.4)(Ba1.6R0.4)Cu3Oz(R=La,Sm,Eu)초전도체의 물과의 반응 안정도

초록

We studied the stability of (Y0:6Ca0:4)(Ba1:6R0:4)Cu3Oz compounds against water by characterizing the structural and the superconducting properties after exposing the pellet samples to distilled water at room temperature for various lengths of time. XRD data reveal that the La-doped sample exhibited tetragonal symmetry whereas the samples with R = Sm or Eu crystallized in the orthorhombic structure, and tetragonality decreasesd with decreasing R-ion radius. Tc determined from resistivity measurements was found to degrade with not only increasing soaking time in water but also decreasing R-ion radius. SEM and solution pH measurements indicated that the Ba atom in the sample easily dissolved out of the lattice as the R-ion size decreases. The observed results suggest that the relative changes in the pH values can be used as a simple index to assess the water corrosion characteristics of superconductors and are discussed in conjunction with a correlation between the stability in water and the tetragonality of the sample.

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