arXiv subjects

Shiv J. Singh

Publications and source records attributed to Shiv J. Singh.

At least 19 recordsLinked to original sources

arXiv2026

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

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.

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arXiv2026

Tuning Superconductivity by Isovalent Antimony Substitution in PrFeAs(O,F)

We investigate the effects of isovalent Sb substitution at the As site in fluorine-doped PrFeAs1-xSbxO0.7F0.3 (x = 0 to 1.0) through structural, Raman spectroscopy, density functional theory (DFT), transport, magnetotransport, and magnetic measurements. The superconducting transition temperature decreases gradually from ~48 K for the parent compound to ~44 K up to x = 0.3, followed by a rapid suppression at higher Sb concentrations due to increasing disorder and secondary phase formation. Raman spectroscopy and DFT reveal lattice expansion and pronounced softening of pnictogen related vibrational modes upon Sb substitution. Magnetotransport measurements up to 9 T show enhanced upper critical fields and increased vortex activation energy for moderate Sb doping, indicating stronger vortex pinning. However, the critical current density remains low because of poor intergranular connectivity. The results demonstrate a crossover from an electronically tuned superconducting state to a disorder-dominated regime in isovalently substituted iron pnictides.

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arXiv2026

Effect of Mn Substitution on Superconductivity in PrFeAs(O,F): Role of Magnetic Impurities

We investigate Mn substitution at the Fe site in PrFe1-xMnxAsO0.7F0.3 (0 to 0.1) using structural, Raman, density functional theory (DFT), transport, and magnetic measurements. X-ray diffraction and Raman analyses confirm preferential Mn incorporation into the FeAs planes, accompanied by lattice expansion and suppression of Fe-related vibrational modes. Electrical transport reveals a systematic decrease of the superconducting transition temperature from 48 K (x = 0) to complete suppression at x = 0.1, together with low-temperature resistivity upturns evolving toward insulating-like behavior. Magnetization and magnetotransport measurements show degradation of superconducting coherence, critical current density, upper critical field, and vortex activation energy with increasing Mn content. The results demonstrate that Mn acts as an efficient magnetic impurity, strongly perturbing the electronic and magnetic environment of the FeAs layers. Comparative analysis indicates relatively enhanced robustness of superconductivity in the Pr-based system, highlighting the role of rare-earth-dependent electronic correlations in impurity effects.

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arXiv2026

Fluorine-substitution-dependent phase diagram and superconducting properties of Sm-based oxypnictides synthesized by a high-pressure growth technique

A series of SmFeAsO1-xFx (Sm1111) bulk samples (x = 0.05 to 0.40) are synthesized by an in-situ cubic-anvil high-pressure technique at 4 GPa and systematically characterized through structural, microstructural, Raman, transport, and magnetic measurements. Structural analysis confirms that the tetragonal Sm1111 phase remains dominant across the entire substitution range, with lattice parameters decreasing smoothly as fluorine content increases, demonstrating effective incorporation of F even in the overdoped regime (x = 0.4). Raman spectroscopy provides complementary, local-phase-sensitive evidence that supports the structural analysis and confirms fluorine substitution in the main Sm1111 phase. In the underdoped region, the superconducting transition temperature (Tc) is enhanced by 10-17 K and the critical current density (Jc) is increased by up to an order of magnitude compared with conventionally synthesized samples at the ambient pressure. The upper critical field, estimated using the WHH model, reaches values approaching 200 T, reflecting strong paramagnetic limitation and multiband effects. TAFF analysis reveals a power-law field dependence of the activation energy, consistent with collective vortex pinning in polycrystalline iron-based superconductors. The superconducting phase diagram constructed from Tc and Jc versus fluorine content reveals a dome-like trend, with a maximum Tc of 57 K and Jc of 10^4 A cm^-2 at the optimal doped region. Comparison with conventionally synthesized Sm1111 samples demonstrates that high-pressure growth significantly extends the effective fluorine substitution range and enhances the superconducting performance, particularly in the underdoped regime. These results establish high-pressure fluorine substitution as an effective materials-engineering approach for tuning the phase diagram and optimizing the superconducting properties of Sm1111.

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arXiv2026

Complete electronic phase diagram and enhanced superconductivity in fluorine-doped PrFeAsO1-xFx

Establishing a complete electronic phase diagram for REFeAsO (RE = rare earth, RE1111) ironbased superconductors has remained experimentally challenging. Here, we report a systematic investigation of PrFeAsO1-xFx over the full nominal fluorine-doping range 0 to 1 and construct the first comprehensive electronic phase diagram for this system. The evolution from the nonsuperconducting parent compound to the fluorine-rich limit reveals a broad dome shaped superconducting region. Structural refinement demonstrates a systematic lattice contraction with increasing fluorine content (x), corroborated by Raman spectroscopy through softening of the Pr(A1g) phonon mode and hardening of the Fe(B1g) mode, confirming effective fluorine incorporation at the oxygen sites. The maximum superconducting transition temperature (Tc) reaches up to 52.3 K, approximately 5 K higher than previous reports for Pr1111. Magnetotransport measurements yield large upper critical fields Hc2(0) exceeding 100 T, while analysis of resistive transition broadening reveals thermally activated flux flow with a crossover from single-vortex to collective pinning regimes. Specific-heat measurements exhibit a reduced jump deltaC/γTc < 1.43, reflecting strong superconducting fluctuations and multiband pairing. These results establish clear structure property correlations and provide a unified description of superconductivity across the entire doping range of the Pr1111 system.

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arXiv2025

Enhancement of the superconducting transition temperature in Mn-doped CaKFe4As4 processed by the high gas-pressure and high-temperature synthesis method

A series of Mn-doped CaKFe4As4 samples, CaK(Fe1-xMnx)4As4 with x values of 0, 0.005, 0.01, 0.02, 0.03, 0.04, and 0.05, are synthesized using two distinct routes: conventional synthesis process at ambient pressure (CSP), and high gas-pressure and high-temperature synthesis (HP-HTS) method. Comprehensive characterizations are performed on these samples to investigate their superconducting properties. This study examines the effects of Mn substitution at Fe sites in the FeAs layer on the superconducting properties of the CaKFe4As4 (1144) material. The HP-HTS process improves the microstructure and phase purity of the parent sample (x = 0), resulting in an enhanced superconducting transition temperature (Tc). In contrast, Mn doping via the CSP method in CaKFe4As4 reduces the sample quality and superconducting performance. Notably, the high-pressure synthesis method leads to an increase in the Tc by 3 to 7 K, particularly at low Mn concentrations. While the critical current density (Jc) of the parent sample (x = 0) shows a significant enhancement under the applied magnetic fields, Jc decreases for Mn-doped CaKFe4As4 bulks. These results demonstrate that high-pressure synthesis is an effective approach to improve the superconducting properties of Mn-doped 1144 compounds.

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arXiv2025

Optimization of superconducting properties of F-doped SmFeAsO by cubic anvil high-pressure technique

We optimize the synthesis conditions for SmFeAsO0.80F0.20 (Sm1111) bulks using a cubic-anvil high-pressure (CA-HP) apparatus through both ex-situ and in-situ processes, applying pressures of up to 4 GPa and heating temperatures of up to 1600°C. A comprehensive characterization has been performed, including structural, microstructural, transport, and magnetic measurements. Our findings indicate that a modest growth pressure of approximately 0.5 GPa is sufficient for the formation of the Sm1111 phase in the ex-situ process. In contrast, the in-situ process requires higher synthesis pressure (4 GPa) and temperature (1400 °C for 1 hour) to achieve the Sm1111 phase with enhanced superconducting properties. Notably, the optimized in-situ process significantly reduces the reaction time needed for the formation of the Sm1111 phase compared to conventional synthesis process at ambient pressure (CSP), leading to an increase in the transition temperature by 3 K and improvements in critical current density (Jc). Conversely, the optimized ex-situ process results in an onset transition temperature (Tc) of approximately 53 K, similar to that of CSP, though it enhances the Jc by an order of magnitude. Despite these advancements, a small amount of impurity phases, as observed during CSP, persists in all Sm1111 samples prepared through either the in-situ or ex-situ CA-HP processes. These results suggest that the in-situ process under optimized conditions (1400 °C, 4 GPa for 1 hour) can effectively improve the superconducting properties of Sm1111. Additionally, a comprehensive analysis comparing these results with high gas pressure techniques, spark plasma sintering, and CSP methods suggests that a small amount of impurity phases in Sm1111 is persistent and cannot be completely eliminated by various pressure techniques, even at the applied pressure of up to 4 GPa.

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arXiv2025

Effect of spark plasma sintering on the superconducting properties of Sm-based oxypnictide

We optimize the superconducting properties of Sm-based oxypnictide (Sm1111: SmFeAsO0.80F0.20) by using the Spark Plasma Sintering (SPS) technique under various synthesis conditions, including heating temperatures ranging from 600 to 1000 °C for durations of 5 to 30 minutes at the applied pressure of 45 MPa. All prepared bulks are characterized by structural and microstructural analysis as well as transport and magnetic measurements to conclude our findings. SmFeAsO0.80F0.20 bulks are also prepared using the conventional synthesis process at ambient pressure (CSP) and the high gas pressure and high temperature (HP-HTS) methods at 500 MPa, which exhibit a superconducting transition temperature (Tc) of ~54 K. Interestingly, the SPS process of SmFeAsO0.80F0.20 increases the sample densities up to 97-98% and confirms the optimized synthesis conditions of 900°C for 5-10 min; however, the increased sintering temperature or duration reduces Tc due to the possible evaporation of lighter elements, particularly fluorine. Furthermore, the SPS technique is unable to reduce the observed impurity phases for the Sm1111, which is similar to the CSP and HP-HTS processes. A slight increment in the Jc by the SPS process is observed due to the enhancement of sample density. A comparative analysis of Sm1111 superconductors prepared by SPS is performed with CSP and HP-HTS processes, suggesting that an increased sample density is ineffective on the superconducting properties in the presence of the impurity phases. This finding can be beneficial for the fundamental and applied research of iron-based superconductor (FBS).

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arXiv2025

Praseodymium doping effect on the superconducting properties of FeSe$_{0.5}$Te$_{0.5}$ bulks under ambient and high-pressure growth conditions

A series of Pr-doped FeSe$_{0.5}$Te$_{0.5}$ (Fe$_{1-x}$Pr$_x$Se$_{0.5}$Te$_{0.5}$; $x = 0$ to 0.3) bulks are prepared by conventional synthesis process at ambient pressure (CSP), and high gas pressure and high temperature synthesis (HP-HTS) methods. These bulks are well characterized by structural and microstructural analysis, Raman spectroscopy, transport, and magnetic measurements. The HP-HTS process of the parent bulks has enhanced the onset transition temperature ($T_c^{\rm onset}$) by 1.5 K and the critical current density ($J_c$) by two orders of magnitude compared to the CSP method. Pr-doped FeSe$_{0.5}$Te$_{0.5}$ up to 10% doping content prepared, either CSP or HP-HTS, slightly increases the unit cell volume, and high-pressure growth produces an almost pure superconducting phase, which confirms the successful Pr-doping at Fe sites. Raman spectroscopy measurements and DFT calculations suggest the substitution of Pr-atoms in the interlayer spacing of Fe(Se,Te) lattice. High-pressure growth of Fe$_{1-x}$Pr$_x$Se$_{0.5}$Te$_{0.5}$ also makes the sample less dense compared to the parent sample grown by HP-HTS. Transport and magnetic measurements depict that Tconset is almost unaffected by Pr-doping, whereas $J_c$ of Pr-doped FeSe$_{0.5}$Te$_{0.5}$ is enhanced by one order of magnitude relative to the parent sample developed by CSP but lower than that of the parent sample grown by HP-HTS. Hence, Pr-doping at Fe sites preserves $T_c^{\rm onset}$ and improves $J_c$ of FeSe$_{0.5}$Te$_{0.5}$ regardless of the doping contents and growth conditions. These results are promising for the practical application of iron-based superconductors to improve $J_c$ properties without affecting $T_c^{\rm onset}$ through CSP process and congruent with discoveries from other superconductors, like cuprates and MgB$_2$.

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arXiv2025

Synthesis and characterizations of arsenic doped FeSe bulks

FeSe(11) family has a simple crystal structure belonging to iron-based superconductors (FBS) and has many stable phases including hexagonal and tetragonal structures, but only the tetragonal phase exhibits the superconductivity. In this study, we have investigated the effects of chemical pressure induced by As-doping at Se-sites in the FeSe system by preparing a series of FeSe1-xAsx (x = 0.005, 0.01, 0.02, 0.05, 0.1, and 0.2) bulks. A broad characterization has been performed on these samples using structural, microstructural, transport, and magnetic measurements. The obtained lattice parameters are increased by As-doping, which suggests the successful insertion of As at Se-sites into the tetragonal lattice for low doping contents up to 5%, whereas the higher As-substitution appears in the form of the FeAs impurity phase. The temperature dependence of the resistivity of all samples has similar behaviour and depicts the highest onset transition temperature of around 11.5 K, but the zero resistivity is not reached until the measured temperature of 7 K, which could be due to the presence of the impurity phases. Our study suggests that a dopant with a large ionic radius, i.e., Arsenic, promotes the formation of the hexagonal phase of the 11 family and is effective for a small amount of doping level for the superconducting properties, whereas higher As-doping levels reduce the superconducting properties.

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arXiv2025

High-pressure growth effect on the properties of high-Tc iron-based superconductors: A short review

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 HPHTS 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.

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arXiv2024

High-pressure growth effects on the superconducting properties of Sm-based oxypnictide superconductors

High-pressure synthesis can be an effective method for improving the sample quality of materials as well as their superconducting properties. In this paper, the synthesis process of F- doped SmFeAsO has been optimized by preparing a series of bulk SmFeAsO0.8F0.2 (Sm1111) using the high gas pressure and high-temperature synthesis (HP-HTS) method, considering various growth parameters like growth pressures (0-1 GPa) and heating time (0.5-2 h). Structural, microstructural, Raman spectroscopic, transport, and magnetic measurements are employed to comprehensively analyze these bulks and derive the conclusive findings. The parent SmFeAsO0.8F0.2 prepared by the conventional synthesis process at ambient pressure (CSP) has a transition temperature (Tc) of around 53-54 K, and the critical current density (Jc) of 103 A/cm2 at 5 K with a small amount of the impurity phases (SmOF and SmAs), consistent with previous reports. Interestingly, all bulks synthesized by HP-HTS have almost the same Tc and Jc as the parent sample. The optimal growth conditions are obtained as 900C, 1 hour, and 0.5 GPa with the sealed Ta-tube, which slightly improved the sample quality and the superconducting properties compared to other bulks grown by HP-HTS. Our study confirms that the existence of the impurity phases in the 1111 family is very robust and cannot be reduced by HP-HTS, leading to only a small variation in the observed superconducting properties of Sm1111 whether prepared by CSP or HP-HTS. This is the first comprehensive investigation of the high-pressure development of Sm1111, which shows distinct behaviour from other families of iron-based superconductors.

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arXiv2024

Copper doping effects on the superconducting properties of Sm-based oxypnictides

A systematic investigation has been performed by synthesis and comprehensive characterization of a series of SmFe1-xCuxAsO0.8F0.2 bulks (x = 0 to 0.2). These samples are well characterized by structural, Raman spectroscopy, microstructural, transport, magnetic measurements, and supplementary calculations within density functional theory (DFT). The parent compound, SmFeAsO0.8F0.2 (Sm1111), exhibits a superconducting transition temperature (Tc) of approximately 54 K. The lattice volume (V) is increased with Cu substitution (x) without observing any impurity phase related to copper, which confirms the successful incorporation of Cu at Fe sites in the superconducting FeAs layers. These analyses are also well in agreement with Raman spectroscopy measurements and relevant DFT results. The superconducting transition is decreased systematically with copper doping and completely suppressed for 7% Cu-doped Sm1111 (x = 0.07). A large amount of Cu substitution (x greater than 0.07) has demonstrated the metal to insulate transition in the low-temperature range, and no impurity phase was observed even at high Cu doping levels (x = 0.2). The calculated critical current density of the parent sample is suppressed with copper substitution, suggesting the reduced pinning centers, sample density, and grain connections, as confirmed by the microstructural analysis. Our studies suggest that the substitution of Cu in the superconducting FeAs layer, resulting the enlargement of the lattice volume, is a source of strong disorder scattering, leading to the suppression of Tc and the emergence of metal-to-insulator, unlike the more successful carrier doping by nickel (Ni) or cobalt (Co), as previously reported.

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arXiv2024

Effect of impurity phase and high-pressure synthesis on the superconducting properties of CaKFe4As4

AeAFe4As4 (Ae = Ca, A = K; 1144) having a transition temperature of 35 K is a stoichiometric family of iron-based superconductors (FBS). Here, we present a detailed study of a high-pressure synthesis of CaKFe4As4 bulks to investigate the impact of these conditions on the superconducting properties of the 1144 family. Additionally, these samples are also prepared by conventional synthesis method at ambient pressure (CSP) and studied the influence of impurities on the superconducting properties of CaKFe4As4. Structural, microstructural, transport and magnetization measurements have been performed to reach the final conclusions. Interestingly, the high-pressure synthesis of the parent CaKFe4As4 compound enhances the transition temperature (Tc) by 2 K and the critical current density (Jc) by one order of magnitude in the whole magnetic field range of 9 T than that of the 1144 bulks prepared by CSP. It suggests the improvement of the pinning centers and grain connections by the high-pressure synthesis approach. Interestingly, our results depict the superconducting onset transition temperature (Tconset) of this stoichiometric 1144 family is robust with the presence of the common 122 (CaFe2As2 or KFe2As2) impurity phases, which is a different behavior compared to other FBS families. However, these impurity phases reduce the grain connections and lead to the phase separation during the formation of the superconducting (1144) phase.

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arXiv2024

Resurgence of superconductivity and the role of $d_{xy}$ hole band in FeSe$_{1-x}$Te$_x$

Iron-chalcogenide superconductors display rich phenomena caused by orbital-dependent band shifts and electronic correlations. Additionally, they are potential candidates for topological superconductivity due to the band inversion between the Fe $d$ bands and the chalcogen $p_z$ band. Here we present a detailed study of the electronic structure of the nematic superconductors FeSe$_{1-x}$Te$_x$ ($0<x<0.4$) using angle-resolved photoemission spectroscopy to understand the role of orbital-dependent band shifts, electronic correlations and the chalcogen band. We assess the changes in the effective masses using a three-band low energy model, and the band renormalization via comparison with DFT band structure calculations. The effective masses decrease for all three-hole bands inside the nematic phase followed by a strong increase for the band with $d_{xy}$ orbital character. Interestingly, this nearly-flat $d_{xy}$ band becomes more correlated as it shifts towards the Fermi level with increasing Te concentrations and as the second superconducting dome emerges. Our findings suggests that the $d_{xy}$ hole band, which is very sensitive to the chalcogen height, could be involved in promoting an additional pairing channel and increasing the density of states to stabilize the second superconducting dome in FeSe$_{1-x}$Te$_x$. This simultaneous shift of the $d_{xy}$ hole band and enhanced superconductivity is in contrast with FeSe$_{1-x}$S$_x$.

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arXiv2023

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 CaKFe4As4 (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 (Tconset) 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 (Jc) 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.

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arXiv2023

Antimony Doping Effect on the Superconducting Properties of SmFeAs(O,F)

We report the synthesis and characterization of a series of antimony-doped SmFeAs1-xSbxO0.8F0.2 (x = 0, 0.01, 0.03, 0.05, 0.1, 0.2, and 0.3) bulks to investigate the twin doping effects on the superconducting properties of SmFeAs(O,F) caused by fluorine (F) incorporation at O-site in SmO layer and antimony (Sb) substitution at As-site in the conducting layer (FeAs). Since the antimony (Sb) has a larger size than arsenic (As), the enhancement of lattice parameters has been confirmed by the XRD analysis. Microstructural analysis confirms that Sb-doping leads to a small improvement in the sample density and an increase in the inhomogeneity of the constituent elements, especially at higher Sb-doping levels. The parent compound SmFeAsO0.8F0.2 has shown the superconducting transition (Tc) at ~54 K, which is systematically reduced with the antimony doping contents (x). Our investigation indicates that the Sb-doped SmFeAs(O,F) phase at low levels is less prone to the multiphase formation than at high levels, which affects the inter- and intragranular behaviour originating from the microstructure nature of 1111 bulks. The critical current density (Jc) of the parent compound has almost the same value as previously reported, which is suppressed slowly with increased Sb-doping. It could be due to the reduced grain connections and the effective pinning centers. This study confirms that the superconducting FeAs layer doping with larger ions at arsenic sites does not support the superconducting properties of Sm1111, which is a distinct behavior from that of Sb-doped CeFeAs(O,F) and LaFeAs(O,F).

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arXiv2023

Optimization of Synthesis Parameters and Superconducting Properties of GdFeAsO1-xFx

REFeAsO (RE1111; RE: rare earth) belongs to the 1111 family of iron-based superconductors (FBS), which illustrates the enhancement of the superconducting transition (Tc) with smaller radii of RE. However, the synthesis of the 1111 phase with a heavy rare-earth is always challenging. In this paper, we report the optimization of the growth and superconducting properties of F-doped GdFeAsO1-xFx bulks by preparing the samples in a wide temperature range (700-1100°C) at ambient pressure. The optimized synthesis parameters are concluded based on structural, microstructural, transport, and magnetic measurements. These findings suggest that the optimal conditions for preparing F-doped Gd1111 bulks involve a two-step process at 900°C for 61 hours at ambient pressure, which is lower than previously reported. The optimized samples have revealed the superconducting transition temperature (Tconset) of 43 K for GdFeAsO0.83F0.17. The first-time reported critical current Jc value for this Gd1111 is observed of the order of 10^3 (A/cm^2) at 0 T and 5 K. Our investigation also concluded that highly pure precursors, particularly gadolinium metal, are required to achieve the superconducting properties of F-doped Gd1111. A high growth pressure of 1 GPa reduces the superconducting properties of F-doped Gd1111.

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