Jae Woong Ko

Microstructure of YBa2Cu3O7-x Superconductor Synthesized with Y2BaCuO5, BaCuO2 and CuO

YBa2Cu3O7-x (123) superconductor was synthesized with pre-synthesized Y2BaCuO5 (211), BaCuO2 and CuO powder. The development of microstructures in this system was studied in detail. Highly densified and well aligned 123 phase can be obtained by a slow cooling heat-treatment and a transient liquid phase sinterting. The presence of transient liquid phase provides a large driving force for the formation of long plate shape 123 grains. Finely and homogeneously distributed 211 particles are trapped in 123 phase. A well-aligned grain structure of 123 phase was produced by the applying of a slow cooling heat-treatment to this system.

The Reaction Sequence in the System Y2BaCuO5–BaCuO2–CuO for YBa2Cu3O7-δ Formation

The reaction sequence among 1 mole of Y2BaCuO5, 3 moles of BaCuO2 and 2 moles of CuO has been studied to provide fundamental understanding for the formation and disapperance of liquid phase in relation with YBa2Cu3O7-δ formation. Reaction between BaCuO2 and CuO starts to form a Ba–Cu–rich liquid phase at 900°C, which reacts with Y2BaCuO5 to give YBa2Cu3O7-δ. This reaction is dominant from 900°C to 920°C range and shows a transient nature. When a considerable amount of YBa2Cu3O7-δ is formed from the reaction, YBa2Cu3O7-δ starts to dissolve in Ba–Cu–rich liquid above 930°C and forms Y–Ba–Cu liquid phase. Upon cooling this Y–Ba–Cu containing the liquid phase crystallises between 940°C and 930°C.