Effects of high-pressure synthesis on phase formation and superconducting properties of PrFeAsO1-xFx

Abstract

Motivated by recent reports of enhanced superconducting performance in several families of iron-based superconductors (IBS) processed by high-pressure (HP) synthesis, we investigate the influence of high gas pressure and high-temperature synthesis (HP-HTS) process on the structural, microstructural, electrical transport, and magnetic properties of Pr-based oxypnictide PrFeAsO1-xFx (Pr1111) using the processing conditions of 0.5 GPa for 1 h previously optimized for other IBS families. Representative underdoped (x = 0.2), optimal doped (x = 0.3), and overdoped (x = 0.5) compositions from the ambient-pressure electronic phase diagram of Pr1111 are selected to evaluate its composition-dependent effects of HP-HTS. The results demonstrate that HP-HTS enhances fluorine incorporation, improves phase formation, and produces a denser microstructure with improved grain connectivity in the underdoped and optimal doped compositions. Magnetic measurements reveal increased in the superconducting transition temperature (Tc) of ~1 K for x = 0.2 and ~6 K for x = 0.3, whereas only a marginal improvement in the critical current density is observed. Electrical resistivity measurements of the underdoped composition show a slight increase in Tc accompanied by a broader resistive transition, indicating residual structural inhomogeneity. In contrast, the overdoped composition exhibits increased impurity phase segregation, accompanied by suppression of superconductivity. These results demonstrate that the effectiveness of HP-HTS in Pr1111 is strongly composition dependent and governed by the interplay among fluorine incorporation, phase stability, and microstructural evolution, highlighting the need for further optimization of the HP-HTS processing conditions.