Published online by Cambridge University Press: 31 January 2011
The microstructures of PrBa2Cu3Oy 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 PrBa2Cu3Oy (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 YBa2Cu3Oy. 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.
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