Silver substitution effect in growth of order in oxygen disorder 123 type cuprate superconductors

Present study reports the dynamics of non-equilibrium ordering in thermally quenched 123 type cuprate superconductor and in its Ag composite. The effect of granularity of these systems in inducing two distinct processes like oxygen ordering in interior of grains due to short range next nearest neighbour interactions (NNNI) and oxygen diffusion to the grain boundaries is investigated. In pure systems the latter process leads to a decrease in Tc when the sample was annealed at room temperature (RT) for a prolonged period. Diffusion of Ag into the grains of Ag-composites however, restricts this process leading to an increase in Tc. The fixed 2-fold oxygen co-ordination of Ag is shown to be responsible for inhibiting oxygen diffusion through grain boundaries. (orig.)