The effect of Gd diffusion upon the structural evolution and superconducting properties of YBa2Cu3O7−x in bulk polycrystalline form was studied. The Gd diffusion in the superconducting ceramic was studied at 600 to 900C by using the energy dispersive X-ray fluorescence technique. The temperature dependence of the Gd diffusion coefficient in grains and grain boundaries were described by:

D (cm2/s) = 8.9 x 10-6 exp[-1.25(eV)/kT]

and

D (cm2/s) = 2.3 x 10-5 exp[-1.09(eV)/kT]

respectively. Magnetization and resistivity measurements showed that the critical transition temperature of Gd diffusion-doped samples increased from 88 to 91K and the critical current density, Jc, which was calculated from M-H loops at 77K, increased from 55 to 122A/cm2 in comparison with those of undoped material. Possible reasons for the observed increases in Tc and Jc due to Gd diffusion were considered. It was found that magnetic hysteresis was enhanced by Gd diffusion.

The Effect of Gd Diffusion-Doped on Structural and Superconducting Properties of YBa2Cu3O7−x Superconductors. K.Öztürk, Ş.Çelik, U.Çevik, E.Yanmaz: Journal of Alloys and Compounds, 2007, 433[1-2], 46-52