Improved critical current densities and compressive strength in porous superconducting structures containing calcium

Templated control of crystallization by biopolymers is a new technique in the synthesis of high temperature superconducting phases. By controlling the way YBa2Cu3O7-delta (Y123) materials crystallize and are organized in three dimensions, the critical current density can be improved. In this work, we present the results of doping superconducting sponges with calcium ions, which result in higher critical current densities (J(c)) and improved compressive strength compared to that of commercially available Y123, in spite of minor reductions in T-c. Y123 synthesis using the biopolymer dextran achieves not only an extremely effective oxygenation of the superconductor but also an in situ template-directing of the crystal morphology producing high J(c), homogeneous superconducting structures with nano-scale crystallinity.