The Melt Process of Tl–Ba(Sr)–Ca–Cu–O Tape-Shaped Wire

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Abstract
The melt process effectively improves crystal orientation, and introduces pinning centers in high-T c oxide superconductors. It is, however, very difficult to apply the melt process to compounds containing volatile elements such as thallium oxide. In this paper, an extremely high-speed zone-melting process (HIZM) of tape-shaped wire in the Tl–Ba(Sr)–Ca–Cu–O system is presented. The HIZM was successfully performed on the Tl-2223 tape with little vaporization of thallium. After solidification, the Tl-2223 matrix transformed to the nonequilibrium phase of 2212 with fine CaO and Cu0 particles. A postannealing was undertaken to retransform the nonequilibrium phases to the equilibrium 2223-phase. It would be possible to control the nonequilibrium CaO phase as pinning center during HIZM and subsequent annealing process.