Critical current density and microstructure of melt-processed YBa 2Cu 3O x with PtO 2 additions

Abstract

YBa 2Cu 3O x (123) with excess Y 2BaCuO 5 (211) in the molar ratio of 5:1 (123/211) were processed using the SLMG (“solid-liquid melt growth”) technique. The effect of PtO 2 on the microstructure and properties of samples with coarse (∼ 1–10 μm) and fine 211 precipitates (on the order of 100 nm) was studied. PtO 2 leads to a decrease in the total volume of the coarser 211 precipitates and segregation of these 211 particles, forming “tracks” of the precipitates within a domain. Also, the morphology of the coarse 211 phase changed to a long acicular shape with PtO 2 additions, as compared with approximately spherical particles in undoped samples. TEM studies revealed the presence of 211 particles of ∼ 100 nm size in both doped and undoped samples with a density of 10 13 / cm 2 along with the coarser 1–10 μm 211 particles. The defect density was found to be higher in the case of PtO 2 doped samples. The intragrain J c measured on powdered textured specimens was found to be enhanced by the PtO 2 additions, especially at low temperatures, despite the fact that the coarser 211 precipitates were inhomogeneously distributed. Magnetization measurements on textured domains also showed an improvement of J c( H‖ c at 1 T) with PtO 2 doping, corroborating the measurements on the powdered samples.