FeSe based superconductors became an applicational research hotspot among iron-based superconductors for the merits of their simplest lattice and nontoxic starting materials. However, there exists a big gap between the superconducting properties of FeSe wires/tapes and single crystals, the reason of which is the complicate phase evolution mechanism of Fe-Se binary system, concluding weak-link of intergrain and excess Fe phenomenon. Therefore, a new dual coordination effect has been adopted to solve these problems via exploring an easy and efficiency chemical elements doping.

A dual-oscillation effect was put forward in F-doped Fe(Se,Te) sample to explain the enhancement of flux pinning, which changes the hexagonal phase from harmful phase to effective pinning center and significantly enhances the activation energy. The Cl doping and hydrostatic pressure process were combined to enhance critical current density in polycrystalline Fe(Se,Te). Cl doping could introduce the point-like secondary phase as pinning center and hydrostatic pressure could strengthen the pinning competence of these point defects. As the result, the critical current density was increased up to 100 times via this dual coordination. An easy and efficiency Ag/O co-doping method was adopted for Fe(Se,Te) to enhance the intergrain connection and removing the excess Fe at the same time,. As a result, the critical current density in both self-filed and high field were greatly increased.

This work provided some new solutions to tune the non-superconducting hexagonal phase, improve intergrain connection, and remove the excess Fe in Fe(Se, Te) polycrystalline, which could play an important role in application of FeSe based wires and tapes in the future.