Properties of Rare-Earth Substitution in Bi(Pb)-2223 Superconductor Prepared by Coprecipitation Method

The superconducting and structural properties of pure and rare-earth elements substituted in Bi (Pb)-2223 samples were investigated. All samples were fabricated by the oxalate coprecipitation (COP) method using metal acetates and oxalic acid as starting materials. The electrical and resistivity were measured by using the four-probe method, while phase purity and microstructural examination were performed by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM). The pure sample has a critical temperature of (Tc zero) 100 K, which decreased to 98, 96 and 97 K for the Eu, Dy and Yb samples, respectively. At 77 K, the un-doped sample gives the highest Jc, which gradually decreases with rare-earth substitution as one move towards the right in the lanthanide series. XRD results reveal two main phases (Bi-2223 and Bi-2212) with decreased amounts of Bi-2223 phases by rare-earth substitution. SEM micrographs showed flaky grains but Yb showed better grain alignment compared with the other substitutions.