Y2BACUO5 PARTICLE COARSENING DURING MELT PROCESSING OF YBA2CU3O7-X

Quenching experiments were carried out to study the coarsening phenome na of Y2BaCuO5 (211) particles in liquid (Ba3Cu5O8) which form as a re sult of the peritectic decomposition of YBa2Cu3O7-x (123) above 1010-d egrees-C. The morphology of 211 particles was observed to become more acicular as the time of hold increased at 1040-degrees-C, showing an a nisotropic growth rate of the 211 particles in the liquid. Also, the c oarsening rate was found to be increased in the presence of excess add ed liquid phase (BaCu5O8) in the 123. Externally added 211 particles w ere found to act as heterogeneous nucleation sites for the peritectica lly formed 211. The observed cored 211 morphology development in the E r 211 doped, melt textured, Y 123 pellets was explained on the basis o f ripening of 211 particles. Reduced coarsening of 211 particles was o bserved in the presence of 0.5 wt.% Pt doping.