THE REACTION SEQUENCE IN THE SYSTEM Y2BACUO5-BACUO2-CUO FOR YBA2CU3O7-DELTA FORMATION

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