Effect of Ag doping on the transition temperature and critical current density of Hg1−xTlxBa2Ca2Cu3O8+δ films fabricated through spray pyrolysis

Abstract The Ag doped Hg(Tl):1223 films have been synthesised by annealing Ba 2 Ca 2.2 Cu 3.3 O z (Ag y ); y = 0, 0.25, 0.5, 0.75, 1.0 precursors deposited by spray pyrolysis on single crystal MgO and ZrO 2 substrates, in controlled Hg-Tl vapour ambient in an evacuated sealed quartz tube at 860°C for 720 minutes. The transition temperature ( T c ), dc transport critical current density ( J c ) and microstructure of the films have been found sensitive to Ag content. The microstructural details as revealed through scanning electron microscopy exhibit the curious characteristics of the existence of spiral like growth feature which is found to deteriorate with increasing Ag concentration. The maximum T c = 126 K of the as synthesized Ag doped film with Ag = 0.50 is nearly the same as the T c = 127 K of oxygen annealed Ag-free films, suggesting in itu oxygenation. The transition temperature has been found to decrease for higher Ag contents (0.50 y J c has been observed to decrease steadily with increase in silver content, being highest (7.2 x 10 4 A/cm 2 , 20 K) in Ag-free case. This decrease in J c has been accounted for in term of formation of Ag(Hg) amalgam due to the reaction of Ag with Hg already present in the grain boundary region.