Recrystallization of YBa2Cu3Ox superconductors in vacuum

YBa₂Cu₃O_x ceramics were recrystallized in vacuum at high temperatures. Recrystallized layers consisting of small grains were observed near the surfaces of the original large-grain 1 2 3 ceramics. The small grains consisted of transformation twins and were identified to orthorhombic 1 2 3 using X-ray diffraction. As vacuum annealing time increased, the thickness of the recrystallized layer increased. The relationship between the thickness and the annealing time showed a linear relationship and an effective diffusion coefficient of 6.25 × 10^–10cm²s^–1. The recrystallized layer showed a critical temperature of 90 K.