Effect of the cycle number of multistep sintering on the properties of FeSe0.4Te0.6 superconductors

FeSe0.4Te0.6 polycrystal bulks were synthesized using the solid‐state sintering method. We developed a novel multistep sintering process and studied the impact of the sintering cycle number. Different cycles of multistep sintering, ranging from one to four cycles were systematically arranged. It was found that the superconducting properties of the FeSe0.4Te0.6 polycrystal bulk using three cycles of sintering surpassed those of other samples, reaching a maximum of Tczero$T_{\mathrm{c}}^{{\mathrm{\ zero}}}$ = 13.4 K, Tconset$T_{\mathrm{c}}^{{\mathrm{\ onset}}}$ = 14.7 K, and a minimum of ∆Tc${T}_{\mathrm{c}}$ = 1.3 K. And the superconducting current density at 4 K reached 1.77 × 104 A/cm2, exhibiting a weak fishtail effect. At 9 K, a composite pinning effect emerged, consisting of normal point pinning and ∆κ surface pinning. The enhancement in superconductivity is attributed to improve uniformity in grain arrangement and more effective element diffusion. After multiple sintering cycles, the stacked grains exhibited increased thickness and the grain arrangement became dense.