Enhancement of Superconducting Properties of Polycrystalline CaKFe4As4 by High-Pressure Growth

High-pressure growth is a unique method to improve the sample quality and size. Here, we have used the high gas pressure and high-temperature synthesis (HP-HTS) method to grow CaKFe 4 As 4 (1144) bulks and investigated their superconducting properties using structural, microstructural, transport, and magnetic studies. The microstructural analysis demonstrates that 1144 samples prepared by HP-HTS have improved the sample density and grain connectivity. The transition temperature ({{T}_c^{onset}}) of 1144 bulks prepared by HP-HTS is increased up to 35.2 K with a transition width ( ΔT ) of 1 K, which is remarkably comparable to the reported 1144 single crystal. Additionally, the critical current density ( J c ) is enhanced by almost one order of magnitude compared with the parent compound prepared by the conventional synthesis process at ambient pressure (CSP), which could be attributed to the improved sample density and effective pinning centers. Our study demonstrates that the sample quality and superconducting properties of various iron-based superconductors can be enhanced by applying the HP-HTS approach, and further research is demanded in this direction.