Microstructural studies of PrBa₂Cu₃O_y during melt processing

Abstract

The microstructures of PrBa₂Cu₃O_y during melt processing have been studied for samples quenched at different stages of the thermal cycle. The absence of the Pr₂BaCuO₅ phase in the Pr–Ba–Cu–O phase diagram, analogous to the Y₂BaCuO₅ (211) phase in the Y–Ba–Cu–O system, makes it interesting to study the microstructure of PrBa₂Cu₃O_y (Pr-123) during melt processing. The nature and morphology of the properitectic particles, the nucleation of Pr-123, and the microstructures resulting from melt processing are investigated and discussed as compared with those in YBa₂Cu₃O_y. At the properitectic stage the morphology of PrBaO₃ (Pr-110) particles is angular. Pr-123 is found to nucleate on all Pr-110 particles with a needle-like morphology, whereas in other 123 systems no preferred morphology for the 123 during nucleation is observed. The melt textured microstructure of Pr-123 revealed similar features like domain formation with the trapped properitectic phase. The only difference is the absence of platelet gaps within domains as observed in other 123 systems. All these observations suggest that as compared to other 123 systems the microstructure of the Pr–Ba–Cu–O system behaves differently due to the absence of the analogous 211 phase.