Large Jc Enhancement of Bi-2212 Ceramics by Triple Doping of Li, K, and Na in Bi1.8-x(Li,Na,K)xSr2Ca1.1Cu2.1Oy (x = 0.05, 0.1, and 0.25) Composition

Abstract

The samples with compositions of Bi1.8-x(Li,Na,K)xSr2Ca1.1Cu2.1Oy (x = 0.05, 0.1, 0.25) were prepared by the solid-state reaction method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and DC magnetization measurements. XRD data indicates that all samples have an ideal ratio of Bi-2212 phase; moreover, some impurity phases such as Bi2CaO4 and Bi4Sr4CaCu3O4 are observed to disappear in the maximum alkaline-doped sample (x = 0.25). SEM observations have shown that, with the increase in the amount of alkaline-doped elements, the grain sizes grow significantly. The highest onset superconducting transition temperature obtained from M-T data belongs to the alkaline-doped (Na, K, and Li) samples at high contents (x > 0.05). It has been found that the sample with x = 0.25 (Na, K, Li) has the largest magnetic hysteresis loop, indicating that high level of triple alkaline element doping positively affects the superconductivity properties of the Bi-2212 phase due to the better intergranular coupling. In addition, Bean’s critical model has been used for determining the critical current density. It has been found that maximum Jc of 141.42 × 104 A/cm2 at H = 1 kOe and T = 15 K is achieved in the x = 0.25 alkaline-doped sample, which is higher than the pure samples obtained by the same initial conditions in literature.