EDXRF measurements on gold diffusion-doped Bi1.8Pb0.35Sr1.9Ca2.1Cu3Oy

Gold (Au) diffusion in superconducting Bi1.8Pb0.35Sr1.9Ca2.1Cu3Oy was investigated over the temperature range 500-800 degrees C by the energy dispersive X-ray fluorescence (EDXRF) technique. It is found that the Au diffusion coefficient decreases as the diffusion-annealing temperature decreases. The temperature dependences of Au diffusion coefficient in grains and over grain boundaries are described by the relations D-1 = 6.7 x 10(-5)exp(-1.19 eV/k(B)T) and D-2 = 9.7 x 10(-4)exp(- 1.09 eV/k(B)T), respectively. The diffusion doping of Bi-2223 by Au causes a significant increase of the lattice parameter c by about 0.19%. For the Au-diffused samples, dc electrical resistivity and transport critical cur-rent density measurements indicated the critical transition temperature increased from 100 to 104 K and the critical current density increased from 40 to 125 A cm(-2), in comparison with those of undoped samples. From scanning electron microscope (SEM) and X-ray diffraction (XRD) measurements it is observed that Au doping of the sample also improved the surface morphology and increased the ratio of the high-T-c phase to the low-T-c phase. The possible reasons for the observed improvement in microstructure and superconducting properties of the samples due to Au diffusion are also discussed. (C) 2008 Elsevier B.V. All rights reserved.