Fabrication of $\hbox{K}_{\rm x}\hbox{Fe}_{2-{\rm y}}(\hbox{Se}_{1-{\rm z}}\hbox{S}_{\rm z})_{2}$ Superconducting Tapes by a Chemical-Phase-Transformation PIT

We have fabricated monocore superconducting tapes of K
_x
Fe
_2-y
(Se
_1-z
S
_z
)
₂
using a process based on a chemical phase transformation from 112-type KFe(Se
_1-z
Sz)
₂
(nonsuperconducting) to 122-type K
_x
Fe
_2-y
(Se
_1-z
S
_z
)
₂
(superconducting) via a supply of Fe from the Fe sheath by annealing. Transformation of tape core from the 112 type to the 122 type was observed at the annealing temperature above 600°C. The obtained superconducting tape showed superconductivity at 29.1 K. The magnetic J
_c
of 1.6 × 10
²
A/cm
²
(at 4.2 K and self-field) was obtained for the sample annealed at 625°C for 5 h followed by quenching.