Abstract
The diffusion reaction between 211 oxide substrate (e. g., 211 is the atomic ratio of RE: Ba: Cu; RE: Gd, Sm, Nd) and 035 oxide coating layer has been studied. Thick and uniform high-Tc superconducting 123 layer is synthesized for all RE systems. Moreover, in Sm and Nd systems the 224 layer is formed between the substrate and the 123 layer. The thickness of the 224 layer depends on the O2 partial pressure when reacted in the mixed gas of O2 and Ar. The formation of the 224 layer is suppressed by controlling the reaction temperature and the atmosphere. The Gd-123 layer formed by the diffusion reaction is composed of relatively large columnar and random grains. The transition temperature (1) of RE-123 phases depends on the O2 partial pressure of O2/Ar mixed gas atmosphere. Tc of the specimen reacted in open air is appreciably improved by the post annealing in O2. The highest offset Tc obtained in the present study for Gd, Sm and Nd systems are 94.0K, 92.3K and 91.4K, respectively, which are higher than that of the Y-123 phase.
