Sintering characteristics of Y-Ba-Cu-oxide-Ag_x superconductors

Abstract

The sintering characteristics of Y-Ba-Cu-oxide (YBCO)-Ag_x (x = 0 to 1.2) using thermomechanical analyzer were systematically investigated to understand the sintering mechanism of the metal superconductor composites. The addition of Ag was observed to lower the sintering temperatures, and the apparent densities of the sintered compacts increased with x from 0 to 0.6. A further increase of x above 0.6 decreased the apparent densities of the sintered compacts. The presence of Ag globules in the YBCO-Ag compacts was observed by scanning electron microscopy and energy dispersive X-ray spectroscopy. The apparent activation energies for sintering of the powder compacts were estimated and observed to vary between 900 to 2000 kJ/mol. The formation of AgO_x by absorbing oxygen from YBCO and sintering atmosphere possibly controls the sintering and superconducting behavior. Incorporation of Ag into the matrix modifies the weak-link characteristics from superconductor-insulator- normal-superconductor (S-I-N-S) to superconductor-normal-superconductor (S-N-S) type.