The effect of Y₂Ba₁Cu₁O₅ addition on microstructure and formation of microcracks in the partially melted Y–Ba–Cu–O oxides

Abstract

In order to investigate microstructural variation by 2-1-1 addition in partially melted Y–Ba–Cu–O, a specimen resulting from 2-1-1 added to 1-2-3 was heat-treated through the peritectic temperature. Microstructure was observed on the directionally solidified region near the interface of the two samples. The 2-1-1 addition results in a homogeneous microstructure where no remnant liquid phase is present. It reduced the 1-2-3 plate thickness, as well as suppressed the formation of microcracks due to the tetragonal-to-orthorhombic phase transition or the thermal contraction during cooling from the peritectic temperature. The formation of microcracks induced by the phase transition seems to be closely related to the process of oxygen diffusion into a sample. We discuss the formation of microcracks in terms of the oxygen diffusion along the plate boundaries and of the thickness of 1-2-3 plates. The decrease in the plate thickness and the fine dispersion of 2-1-1 particles contribute suppression of the formation of microcracks and their propagation.

The isothermal melt-texturing of bulk YBa2Cu3O7-xceramics: from cooking to modelling

“…The trapping of the 211 particles and the presence of unreacted L phases seem to be inherent to the melt-textured growth process. In order to avoid the segregations of the L phase at the grain boundaries, several authors have proposed to add an excess of some 211 phase in the melt [32,33]. This addition should favour the completion of the peritectic reaction.…”

“…It is now accepted that some addition of 211 phase improves effectively the stability of J c as a function of an external magnetic field by increasing the density of pinning centres and limiting the secondary phases at the grain boundaries [34]. Microstructural, mechanical and superconductivity properties are improved [33,35]. It is of interest to know what quantity of 211 phase should be added for the optimum situation of a technological property.…”

Mechanical properties and field trapping ability of bulk superconductors with resin impregnation

“…Due to this fact, cracks are sometimes introduced in the sample even in the as-grown state [4]. Macro-cracks often nucleate from the growth-related defects [5][6][7][8]. There is another chance that micro-cracks formed as a result of different thermal expansion coefficients between RE123 and RE211 phases grow on further cooling [9][10][11][12].…”

Thermal investigations of reactive powder mixtures as precursors for melt-processing of YBa2Cu3O7−x

“…The critical current density of the processed samples depends on composition, the size of the precursors and the thermal processing (sintering [10][11][12], high-pressure sintering [13,14] and texturation [9,[15][16][17]) and has values of 102-104-A/cm 2. E x p e r i m e n t a l Pure phases of BaCuO2, YBa2Cu307_ x, Y2BaCuO5 and Y2Cu205 were prepared via solid state reactions, using either stoichiometrical mixtures of BaCO3, CuO and Y203 or coprecipitated oxalates.…”