Properties of YBa2Cu3AgxO7−δ composite superconductors

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Abstract
Superconducting properties and microstructures of the YBa2Cu3AgxO7−δ composites have been studied as a function of silver content, 0<xTc of these composites was found to be the same, ∼90 K, for the above range of composites. For values of x>3, small quantities of 211 phase were detected along the grain boundaries. Alloy formation between Ag and Cu is proposed to take place which makes the residual composition poor in copper, resulting in the formation of nonsuperconducting 211 phase. The silver is observed in the form of precipitates at very low concentrations of silver, indicating that silver does not substitute for copper in YBa2Cu3O7. Lattice parameters of the composites were found to be invariant throughout the above composition range. The addition of Ag2O in the starting composition seems to stabilize the stoichiometric YBa2Cu3O7 by way of decomposition to Ag and O. As a result, the incorporation of oxygen and recovery of superconducting properties is enhanced in the silver composites.