Li Doping into the Pb substituted Bi-2212 Phase by Electrochemical Mechod

Abstract

Effects of electrochemical Li-doping to the Pb-substituted Bi-2212 phase on its structural and superconducting properties were studied. Bi_1.8Pb_0.2Sr_1.5Ca_1.5Cu₂O_z was lithiated through an electrochemical method at constant applied potential at room temperature. In the electrochemically Li-doping samples, the original crystal symmetry, tetragonal structure, was maintained and any secondary phase was not formed. The amount of doped Li for Bi_1.8Pb_0.2Sr_1.5Ca_1.5Cu₂O_z was much lager than that for Bi₂Sr_1.5Sr_1.5Ca_1.5Cu₂O_z at the same reaction periods. Analysed maximum Li content y for Li_yBi_1.8Pb_0.2Sr_1.5Ca_1.5Cu₂O_z was found to be 0.53, which was remarkably high in comparison with y=0.37 for Li_yBi₂Sr_1.5Ca_1.5Cu₂O_z The lattice parameters (a, c) of Li_yBi_1.8Pb_0.2Sr_1.5Ca_1.5Cu₂O_z increased continuously in a similar trend to that of Li_yBi₂Sr_1.5Ca_1.5Cu₂O_z Tc remains almost constant around 85K as the Li content y increased.