Effect of Yb, Gd, and Nd substitution at the Sr site on the metal-insulator transition of the (Bi,Pb)-2212 system

Abstract

Resistivity measurements in the temperature range (64-300 K) were used to study the metal-insulator transition (MIT) driven by a change in the carrier concentration of the Bi(1.7)Pb(0.4)Sr(2)Ca(1.1)Cu(2.1)O(y) [(Bi,Pb)-2212] system. The carrier-concentration is changed by substituting rare-earth (RE) elements (Nd, Gd, and Yb) at the Sr site of (Bi,Pb)-2212. Results show that at higher levels of RE substitution, MIT occurs in (Bi,Pb)-2212, during which the resistivity becomes minimum at a particular temperature(T(min)) for a particular doping level. Below this temperature, resistivity increases with a decrease in the temperature and vice versa, showing an insulating and a metallic nature, respectively. This T(min) and the carrier concentration at which MIT occurs depend on the substituted RE.