Influence of alkaline metal Li1+ intercalation on the excess conductivity, thermopower and hardness of BSCCO pellets

A series of pellet materials with nominal compositions Bi2Sr2Ca4Cu6Pb0.5LixOy (BSCCO) (x=0.0, 0.1, 0.2, 0.3, and 0.5) has been prepared by ordinary powder reaction method and analyzed by X-ray powder diffractometer (XRD), scanning electron microscope (SEM), their electrical resistivity (ρ) and their thermoelectric power (TEP) were also measured. The nature of the temperature dependence of ρ and TEP was strongly influenced by the presence of the lithium (Li) intercalation. The attempt to fit the thermoelectric data to an expression of the form: S=AT+B/T has been successful. Analysis of our data indicates that the TEP precursor peak near T>T0c arises due to superconducting fluctuations. On the other hand, the Vickers microhardness (VHN) of Li samples enhances with increasing Li intercalation up to x≈0.3. This improvement of VHN may be attributed to dispersion hardening of the high-Tc phase (2 2 2 3) grains. More intercalation of Li (x=0.5) showed adverse effect on VHN and density of investigated samples, this opposite trend may be due to structural imperfection.