Effect of nano-particles SnO2 and CeO2 addition on the Y123/Y211 sample grown in a microwave furnace

It is well known that the critical current density (J(c)) of Y123 bulk supe rconductor can be increased by the introduction of non superconducting flux pinning centers such as small secondary phases precipitates (1 mum(3)). Th us, several studies have shown that the introduction of CeO2 and SnO2 powde rs allows the formation of micron size secondary phases homogeneously distr ibuted in the Y123 matrix allowing an increasing of J(c). As the precipitat es size should be a crucial parameter that affects pinning properties of Y1 23, this work is devoted to compare, in terms of microstructure and superco nducting properties, the effect of micrometric and nanometric SnO2 particle s addition in the 'SnO2 + CeO2' doped sample. It was shown that the additio n of nanometric SnO2 particles, compared with an addition of micronic SnO2 particles, induces an increasing of the reactivity between the liquid phase and the dopants. Then, Y211 coarsening is not reduced and micronic seconda ry phases is formed conducting to obtain no improvement of the superconduct ing properties. (C) 2001 Elsevier Science Ltd. All rights reserved.