The influence of metallic interfaces on the properties of (Hg, Bi)Ba2Ca2Cu3Oy superconductors

The influence of AgPd and Au interfaces on the formation of the (Hg, Bi)Ba2Ca2Cu3.1Oy (HgBi-1223) superconductor was investigated. Variations in the BaCaCuO precursor phase assemblage and the use of Bi2CuO4 as the Bi source were examined in an attempt to lower the reaction temperatures suitable for the growth of HgBi-1223 in conjunction with AgPd and Au substrates. Phase pure samples of HgBi-1223 were synthesized at temperatures below 850 deg. C. Use of Bi2CuO4 as a Bi source combined with variations of the BaCaCuO precursor phase assemblage allowed the formation of some liquid phase during the reaction and resulted in dense HgBi-1223 samples with aligned colonies of grains. Magnetization measurements in fields up to 30 T indicated good intergrain coupling within the large grain colonies. Comparison of the microstructural features of bulk samples and the metal-superconductor interface showed that the interface has a positive influence on grain growth and alignment. The metallic interfaces, however, were found to have a detrimental effect on the purity of the superconducting phase due to the formation of amalgams. (author)