Effects of residual carbon on phase formation of TlBa 2Ca n−1 Cu nO y ( n=3 and 4) superconductors

Abstract

The effects of residual carbon in precursors on phase formation of single Tl–O layer superconductors of TlBa 2Ca n−1 Cu n O y ( n=3 and 4) have been investigated. The samples were prepared from Tl 2O 3 and precursors of Ba 2Ca n−1 Cu n O 2 n+1+ δ (C x ) ( n=3 and 4) with various residual carbon contents ( x=0.02–0.19). Even a small amount of carbon promotes the formation of double Tl–O layer phases of Tl 2Ba 2Ca n−1 Cu n O y ( n=3 and 4). Using the carbon reduced precursor ( x=0.02), a TlBa 2Ca 2Cu 3O y phase is synthesized directly in a silver-sheathed tape without such elements as Pb, Bi and Sr.