Superconducting Phase Control for Rare-Earth-Free High-Tc Superconducting Thin Films

Abstract

Much attention has been paid to the rare-earth-free high-Tc oxide superconductors of the Bi-Sr-Ca-Cu-O and Tℓ-Ba-Ca-Cu-O. Recent studies suggest that these rare-earth-Cree superconductors show a layered structure comprizing Bi-O and Cu-O₂ layer and the critical temperature Tc varies with the numbers of the Cu-O₂ layer. Typical rare-earth-free high-Tc oxide superconductors are listed in Tab. 1 [1–11]. The Bi₂Sr₂CaCu₂O_x comprising two Layers of the Cu-O₂ exhibits Tc ⋍ 80 K (2-2-1-2 structure) and the Bi₂Sr₂Ca₂Cu₃O_y comprising three layers of the Cu-O₂ exhibits Tc ⋍ 110 K (2-2-2-3 structure). Further increase of the Cu-O₂ layers is expected to increase the Tc.