Experimental data collected for the preparation of the manuscript: "High-pressure growth effect on the properties of high-T_c iron-based superconductors: A short review"

Cryogenics 147 (2025) 104028

Abstract:

The high-pressure growth technique is a vital approach that facilitates the stabilization of new phases and allows for meticulous control of structural parameters, which significantly impact electronic and magnetic properties. We present a short review of our ongoing investigations into various families of iron-based superconductors (IBS), employing the high-gas pressure and high-temperature synthesis (HP-HTS) method. This technique is capable of producing the gas pressures up to 1.8 GPa and a heating temperature of up to 1700 ◦C through a three zone furnace within a cylindrical chamber. Different kinds of IBS samples are prepared using HP-HTS and characterized through various measurements to reach the final conclusions. The results demonstrate that the high-pressure growth technique significantly enhances the properties of IBS, including the transition temperature, critical current density, and pinning force. In addition, the quality of the samples and their density are improved through the intergrain connections. Furthermore, the comprehensive evaluations and investigations prove that a growth pressure of 0.5 GPa is sufficient for producing high-quality IBS bulks under the optimized synthesis conditions.

[In the published article, Figure 1 is a block diagram of high-pressure technique.]

• Figure 1: Block diagram of HP-HTS technique, which includes a three-stage oil-based compressor, a high-pressure chamber, and a control unit monitor. “A” and “B” depict a set of key valves to control the pressure through the oil pump for the three pistons: 1, 2 and 3 sustaining pressures of 0.08 GPa, 0.4 GPa and 1.8 GPa respectively. “C” represents a set of key valves to control the gas pressure for the three pistons.
• Figure 2: The synthesis pressure dependence of (a) hexagonal H-phase calculated from XRD patterns, (b) the Tconset , (c) the Jc values at 0 T and 5 T, and (d) the calculated pinning force (Fp) at the applied magnetic field of 5 T for various FeSe0.5Te0.5 prepared by HP-HTS.
• Figure 3: The variations of (a) the Tconset , (b) the Jc value at 0 T and 5 T, (c) the calculated pinning force (Fp) at the applied magnetic field of 5 T for the prepared bulk CaKFe4As4 samples with respect to the synthesis pressure.
• Figure 4: The synthesis pressure dependence of (a) the variations of the Tconset for G0-G4 (G-batch) and parent (P) samples, and (b) the Jc values at 0.2 T and 8 T, (c) the calculated pinning force (Fp) at 0.2 T, 8 T, and 5 K for G2, G4 and the parent (P) samples.