CaSiO₃ as a substrate material for Ba-Y-Cu-O superconducting oxide films

The reactivities of Ba₂YCu₃O_7-x with BaZrO₃ and CaSiO₃ were studied to develop a substrate material for superconducting oxide films. It was found that BaZrO₈ and CaSiO₂ were less reactive to Ba₂YCu₃O_7-x and the onset critical temperature of Ba₂YCu₃O_7-x remained unaltered after heating in contact with these materials at 1223 K. Although BaZrO₂ was less reactive than CaSiO₃, BaZrO₃ was unsuitable for the substrate of Ba₂YCu₃O_7-x films because of the large difference of the thermal expansion coefficient. On the other hand, the thermal expansion coefficient of CaSiO₈ is almost the same as that of Ba₂YCu₃O_7-x. High-T_c superconducting oxide films were prepared easily on the CaSiO₃ substrate by the conventional dipping-pyrolysis method. As a result, mixed oxide, CaSiO₂, is one of the promising materials for the substrate of Ba₂YCu₃O_7-x films because of its low cost, low reactivity, and comparable in thermal expansion coefficient.