Influence of Ag substrates on grain alignment and critical current density of Bi-2212 tape conductors

We investigated the influence of Ag substrate on the microstructure and J(c) values of dip-coated Bi-2212/Ag tapes. The grain alignment of Bi-2212 in the oxide/Ag interface was much higher than that in the free surface of oxide. J(c) increases with increasing oxide/Ag interface area and with decreasing oxide layer thickness, while J(c) was almost independent of the free surface area. The smoothness of the Ag substrate is also an important factor. Micrometer-size roughness of the Ag substrate results in a decrease of Bi-2212 grain alignment and therefore J(c). Addition of alloying elements to the Ag also degrades the grain alignment of Bi-2212 and decreased J(c). Cold rolling before the heat treatment improved the grain alignment and enhanced J(c).