Effect of AgNO3 additive/doping on microstructure and superconductivity of the Pb doped Hg: 1223 thin film prepared through spray pyrolysis

We report successful fabrication of Ag doped Hg:1223 films by reacting Ba₂Ca_2.3Cu_3.3O_z(Ag_y): y=0, 0.02, 0.025, 0.05, 0.1 and 0.2 precursors deposited by spray pyrolysis on SrTiO₃ (100) substrates, in controlled Hg+Pb ambient, in an evacuated sealed quartz tube at 820 °C for 4 h. The effects of AgNO₃ addition on the superconducting properties of Hg/(Pb):1223 films are studied. The addition of low concentration of silver e.g. y≈0.025 results in a slight increase in T_c (R=0) from 125 to 126 K and the dc critical current density (J_c) decreases with the increasing Ag in Hg(Pb):1223 (Ag_y) films. The microstructural details exhibit the curious characteristics of spiral like features for lower concentrations of silver i.e. up to y=0.05. These improvements are believed to be due to the liberation of oxygen through the dissociation of AgNO₃ at higher temperature and passivation of weak link effects through the segregation of silver at these grain boundaries. The addition of silver content y≥0.05 resulted in the decrease in transition temperature. The J_c is observed to decrease steadily with increasing Ag content. The microstructural features, e.g. spiral are also found to deteriorate with increasing silver content. The deterioration in superconducting properties at high Ag content is believed to be mainly due to the formation of Ag-Hg amalgam.