Electrochemical lithium intercalation into the Bi-2212 phase

Abstract

Effects of lithium intercalation into the Bi-2212 phase on its structural and superconducting properties were studied using monophasic samples of Bi 2Sr 1.5Ca 1.5Cu 2O z lithiated through an electrochemical method at a constant applied voltage at room temperature. The amount of doped lithium was found by 1CP analysis to be in the range of 0 ≤ y ≤ 0.37 for Li y Bi 2Sr 1.5Ca 1.5Cu 2O z depending upon experimental conditions. However, the oxygen content determined by coulometric titration remained almost unchanged after the lithiation. The electrochemical lithium intercalation led to a very interesting change in T c though the original tetragonal structure and oxygen content remained essentially the same: T c first increased rapidly as y increased, reached a maximum of 94 K, and then decreased to zero. The drastic T c change is ascribed to a decrease in the hole concentration. Thus, the electrochemical lithium-doping provides us with a great advantage of easily controlling T c at room temperature by changing electrochemical conditions while keeping the original crystal symmetry.