Nano-Al2O3 particle addition effects on YBa2Cu3Oy superconducting properties

The effect of nanometer Al2O3 particle addition on the crystal structure and superconducting properties of YBa(2)Cu(3)Oy (YBCO) ceramics was systematically studied. Samples were synthesized using a standard solid state reaction technique by adding alumina up to 0.8 wt%. The structure for all samples was characterized by X-ray diffraction (XRD) with the Rietveld refinement technique and by the energy dispersive X-ray (EDX) technique. The crystal lattice parameters were found to change and the orthorhombicity decreased slightly with Al2O3 addition. No change in the structural symmetry state was obtained. Aluminium was found to incorporate into the crystal structure and could occupy both copper in chains Cu(1) and yttrium (Y) atoms. With the increase of Al2O3 addition, the superconducting transition temperatures determined by standard four-probe method measurements changed slightly to 85 K up to x = 0.6 wt%, then dropped sharply with higher alumina content. Results are discussed in relation with the importance of Al incorporation in Y, Cu(1) sites and oxygen stoichiometry to superconductivity in YBCO. Significant enhancement of the superconducting critical current density (J(C)) in applied magnetic field was evidenced for the nanometer Al2O3 added samples. (c) 2006 Elsevier Ltd. All rights reserved.