Origin of the silver doping effects on superconducting oxide ceramics

The origin of silver doping effects on Y-Ba-Cu-O superconducting ceramics, such as a high-temperature shift of the point at zero resistivity in resistivity measurements and an increase in critical current density, was sought by transmission electron microscopy observations. Sintering was strongly promoted together with suppression of the formation of the liquid phase in the grain boundaries by silver. Consequently, the liquid phase, which is not a superconductor, was not present in almost all the grain boundaries of the silver-doped ceramics, while this phase was present in almost all the grain boundaries in pure ceramics.