Structure of Different RE-123 Phases Synthesized by the Diffusion Reaction

Thick and uniform RE-123 oxide layers (RE: Ho,Dy,Gd,Sm,Nd ; 123: atomic ratio of RE:Ba:Cu) have been synthesized in a relatively short reaction time in diffusion composites composed of RE-211 oxide substrate and 035 oxide coating layer. The thickest 123 layer, about 300μm in thickness, has been obtained in the Gd-based composite. The addition of Ca2Cu03 to the substrate yields further increase in the Gd-123 layer thickness. The 224 layer is formed between the 123 layer and the substrate in Sm-based and Nd-based composites. The formation of 224 layer is suppressed by adjusting the reaction temperature and the O2 partial pressure of O2/Ar mixed gas atmosphere. The T c and the transition width of Ho-based, Dy-based and Gd-based composites do not depend much on the O2 partial pressure, while those of Sm-based and Nd-based composites strongly depend on it Offset J c ’s of over 90K have been obtained in all RE-based diffusion composites.