| Abstract |
In this work we present the results about the preparation of the superconductor
YBa2Cu3O7-δ (Y123) by sol-gel method using oxalate precursors. Samples were prepared by
dissolving stoichiometric mixtures of Y(OOCCH3).4H2O, Ba(OOCCH3)2 and Cu(OOCCH3)2.H2O
acetates in aqueous solution of oxalic acid, HCOO-COOH. The particulate sols obtained (2g.) were
divided in two parts (1g. each one), from which the first one (sample A) was grinded, pellet,
calcined (860ºC) and sinterised at 860ºC in oxidizing atmosphere, the second part (sample B) was
grinded, pellet, calcined at 880ºC and finally sinterized at 880ºC in the same conditions, the XRD
revels the superconductor Y123 is formed in the first sample, but coexisting with remarkable
presence of the secondary phases: CuO, BaCu3O4, BaCO3 and BaCuO2, while in sample B the XRD
reveals the obtention of high purity monophase Y123, the ac susceptibility measurement using a
Quantum Design (SQUID) magnetometer indicates TC(onset)=92K for this sample, moreover the
Rietveld refinement was done taking the orthorhombic Pmmm Y123 spatial group as a model, this
suggest the cell´s parameters a=3.839Å, b=3.899 Å and c=11.702Å as reported in the literature.
Therefore for the preparation of Y123-superconductor using oxalate precursors, the optimus
sintering temperature is 880ºC. |
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