Synthesis of YBa2Cu3O7-δ Using Oxalate Precursors and Sol-Gel Method

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 (860°C) and sinterised at 860°C in oxidizing atmosphere, the second part (sample B) was grinded, pellet, calcined at 880°C and finally sinterized at 880°C 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 880°C.