Doping controlled metal to insulator transition in the (Bi, Pb)-2212 system

We report on the details of the metal-insulator transition in the Bi1.7Pb0.4Sr2-xPrxCa1.1Cu2.1O8+δ system, in the concentration range of x = 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.3 and 1.5. In addition to the electrical resistivity measurements at 6-300 K, the phase, microstructural and elemental analyses were also carried out to assess the relative performance of the samples. A detailed analysis of measurement results reveals that Pr atoms are successfully substituted at the strontium site of the (Bi, Pb)-2212 system. The system is found to be superconducting in the doping range of x≤0.6 and semiconducting for x≥0.7. A metal to insulator transition is found to occur in the doping range 0.6<x≤0.7, and the results reveal that a disorder induced transition leads to the localization of states in the vicinity of the Fermi level and to the said phenomenon in the Pr substituted (Bi, Pb)-2212 system. Resistivity in the insulating regime of samples was analyzed using a generalized hopping approach and the transport mechanism is found to be governed by the VRH mechanism. Superconductivity in conjunction with 2D VRH is observed near the superconductor-insulator boundary and is in agreement with a theoretical model that considers the competition between superconductivity and localization in a disordered system.