Properties of ag-doped $Bi_{1.6}Pb_{0.4}Sr_2Ca_3Cu_{4-x}Ag_xO_y$ (2234) oxides prepared by S.S.R. method

Özet

The effect of Ag-doping $Bi_{1.6}Pb_{0.4}Sr_2Ca_3Cu_{4-x}Ag_xO_y$ compounds (x=0.0-1.0), prepared by conventional Solid-State-Reaction (SSR) technique, was studied using x-ray diffraction (XRD) and electrical resistivity. The high-$T_c$ fraction of the 2223 phase, formed from the nominal composition of 2234, decreases with increasing Ag content. From lattice parameter calculations it follows that Ag-doping the unit cell phase of $(Bi,Pb)_2Sr_2Ca_2Cu_3O_y$ is limited to the value of $x\leq0.1$. The zero resistance critical temperature $(T_{c,zero})$ was determined from the resistivity curves for all samples. The value of $T_{c,zero}$ decreases slightly to 106 K for $x\leq 0.4$ and when the nominal silver content increases up to x=0.7 or more $T_{c,zero}$ strongly decreases to 72 K. The critical current density $J_c$ at 77 K decreases dramatically as silver content increases. This result is discussed on the basis of precipitation of low-$T_c$ 2212 and other impurity phases in $Bi_{1.6}Pb_{0.4}Sr_2Ca_3Cu_{4-x}Ag_xO_y$ compounds