Crystallization and in-plane alignment behavior of YBa₂Cu₃O_7−y films on MgO(001) prepared by the dipping-pyrolysis process

The effects of annealing temperature and oxygen partial pressure [p(O₂)] were investigated on the crystallization and orientation of YBa₂Cu₃O_7−y (YBCO) films on MgO(001) prepared by the dipping-pyrolysis process. The c-axis oriented films without in-plane alignment were prepared by annealing in the YBCO-unstable region, i.e., at low initial p(O₂) of 10₋₄−10₋₃ atm and 950 °C followed by O₂ treatment, through intermediate Y₂BaCuO₅ and liquid phase. In-plane aligned c- or c/a-axis films were prepared by similar heat treatment with an initial p(02) of 10₋₄ atm and 900–925 °C through a mixture of BaCu₂O₂ and YBa₃Cu₂O_6+x. In contrast, nonoriented YBCO films were obtained by annealing at higher initial p(O₂)'s and lower temperatures, i.e., by direct reaction among Y₂O₃, BaCO₃, and CuO.