1Institute of Physics and Beijing National Laboratory for Condensed Matter Physics, Chinese Academy of Sciences, Beijing 100190 2School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049 3Collaborative Innovation Center of Quantum Matter, Beijing 100190
Abstract：We report a direct microwave synthesis method for the preparation of 11-type high quality Fe(Te,Se) polycrystalline superconductors. The bulk samples are rapidly synthesized under the microwave irradiation during several minutes, with a subsequent annealing process at 400$^{\circ}\!$C. The samples exhibit a nearly single phase of the tetragonal PbO-type crystal structure with minor impurities. Morphology characterization shows high density, tight grain connectivity and large grain sizes around 100 μm with small cavities inside the sample. Resistivity and magnetization measurements both show similar superconducting transitions above 14 K. The magnetic hysteresis measurements display broad and symmetric loops without magnetic background, and a high critical current density $J_{\rm c}$ about $1.2\times10^{4}$ A/cm$^{2}$ at 2 K and 7 T is estimated by the Bean model. Compared with the solid-state reaction synthesized samples, these superconducting bulks from microwave-assisted synthesis are possibly free of the interstitial Fe due to smaller $c$-axis, higher $T_{\rm c}$ in magnetic transitions, better $M$–$H$ loops without magnetic background and greatly enhanced $J_{\rm c}$, and are promising as raw materials for the non-toxic Fe-based superconducting wires for large currents and high field applications.
2019, Vol. 36 
