The influence of starting particle size and Pt/Ce addition on the microstructure of melt processed bulks

Abstract

Y-Ba-Cu-O melt processed samples were prepared from mixtures of powders (starting average particle size ranging from to ) with and 1 wt% or 1 wt% . The resulting microstructure of the samples was composed of network and low concentration regions with size and morphology correlating with the starting powder size independently of the holding time in the melted state. The 211 particle size was smaller for Ce doped samples than for Pt doped samples. The differences in porosity of Pt and Ce doped samples were related to the changes in the interfacial energy of the constituent phases.

Record critical current densities in IG processed bulk YBa2Cu3Oy fabricated using ball‐milled Y2Ba1Cu1O5 phase

“…. Additionally, the combined addition of Pt and CeO 2 are reported to yield the best performance of Y‐123 or LRE‐123 melt‐processed materials, which always exhibited high critical currents and improved trapped field values . The top‐seeded melt‐growth process has been routinely used for the batch production of single‐grain Y‐123 and LRE‐123 bulk superconductors .…”

Oscillation of Y2BaCuO5 particle concentration in the melt-grown YBaCuO bulk superconductors

“…Appearance of nests with very small 211 particles can be, in our opinion, associated with agglomeration of small powder particles during dry milling [11]. These agglomerates are than ''copied'' to final microstructure after melt growth similarly as other inhomogeneities [7].…”

“…The most important are macroscopic 211 concentration inhomogeneity in the growth sectors and higher 211 concentration in the c-GS than in the a-growth sectors (a-GSs), which are caused by the anisotropic 211 particle pushing by growth front [5,6]. Microscopic inhomogeneity inside growth sectors can occur in the form of 211 free regions, which have been associated with the presence of large particles in starting 123 powder [7,8] or they are formed by filling of bubbles by melt [9]. The growth subsectors with lower or higher concentration of 211 particles were related to formation of growth macrosteps at the growth front [10].…”

Functional imaging and assessment of the glucose diffusion rate in epithelial tissues in optical coherence tomography

“…Briefly put, Diko et al argue that the LCRs are caused by large Y123 grains in the starting powder that melt during heating, are subsequently unaffected by other additives and resolidify to form large, stoichiometric Y123 regions [14]. On the other hand, Kim et al propose that LCRs are the result of pores in the sample that have evolved during melting of Y123 and are then filled by the liquid phase [13].…”

“…These pockets later transform into regions of Y123 which do not contain Y211 particles, due to the local deficiency of Yttrium in these areas. The second, by Diko et al [14], claims that the areas are formed from large Y123 particles in the starting powder that melt, do not mix with the rest of the Y211 and liquid phases, and later re-form into essentially stoichiometric Y123 regions. It is not clear which of these effects plays a more important role in the formation of these regions.…”