Electrical transport and small polaron hopping conduction in Mn-doped Bi3PbSr3Ca3Cu4−mMnmOx glasses: precursors for high temperature superconductors

Multicomponent Bi3PbSr3Ca3Cu4−mMnmOx (m=0, 0.02, 0.03, 0.04, and 0.06) glasses, precursors for high temperature superconductors, have been prepared by fast quenching technique from their melts. These are n-type semiconductors and follow non-adiabatic small polaron hopping conduction mechanism above 12θD (where θD being the Debye temperature). The lower temperature (below 12θD) conductivity data can be fitted with the variable range hopping (VRH) model. The estimated Mott parameters are found to be reasonable for the formation of small polaron and comparable with those of some other similar glasses. However, compared to the usual binary or ternary transition metal oxide glasses, the density of states at the Fermi level N(EF) is found to be one order of magnitude higher which we consider to be due to the formation of nanocrystalline (5–20 nm) clusters in these glasses. All the glasses are found to become superconductors in their glass–ceramic phases and the corresponding superconducting transition temperature decreases continuously with increase of Mn content indicating pair-breaking mechanism.