Synthesis of RE (Gd, Sm, Nd) Ba₂Cu₃O_7−x Superconductors through the Diffusion Process

Abstract

The diffusion reaction between 211 oxide substrate (where 211 represents the atomic ratio of RE:Ba:Cu; RE: Gd, Sm, Nd) and 035 oxide coating layer has been studied. Thick and uniform 123 layer is synthesized for all RE systems. Moreover, in Sm and Nd systems 224 layer is formed between the substrate and the 123 layer. The thickness of 224 layer depends on the 02 partial pressure when reacted in the mixed gas of O₂ and Ar. The formation of the 224 layer is suppressed by changing 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 (T _c) of RE-123 phases depends on the O₂ partial pressure of O₂/Ar mixed gas atmosphere. T _c of the specimen reacted in open air is appreciably improved by the post annealing in O₂. The highest offset T _c obtained in the present study for Gd, Sm and Nd systems are 94.0 K, 92.3 K and 91.4 K, respectively. The formation of thick Gd-123 layers on Ni tape has been also performed through the diffusion reaction.