Microstructural Study of the Effect of an Excess of Y_2BaCuO_5 and BaSnO_3 Doping on the Texturing Process of YBa_2Cu_3O_(7-x) Bulk Superconductors

摘要

Melt texture process of YBCO leads to a YBa_2Cu_3O_(7-x) matrix where Y_2BaCuO_5 particles are observed. The Y_2BaCuO_5 inclusions size and distribution depend upon several parameters: YBa_2Cu_3O_(7-x) grain size in the presintered, heating rate, dopants. The influence of an excess of Y_2BaCuO_5 and/or BaSnO_3 on these Y_2BaCuO_5 particles are observed in the liquid phase and in the texture domain. According to the dopant used, two kinds of coarsening of Y_2BaCuO_5 can be observed: an isotropic and an anisotropic. The control of the distribution of Y_2BaCuO_5 particle size is of primary interest to improve the efficiency of the MTG process. In particular large cooling rate (5℃/h) during the texture formation could be used by adding Y_2BaCuO_5 + BaSnO_3 to YBa_2Cu_3O_(7-x) composition.