The role of chemical composition in the synthesis of Ca/K-1144 iron based superconductors

Masi, Andrea; Armenio, A. Angrisani; Celentano, G.; Barbera, A. La; Rufoloni, A.; Silva, Enrico; Vannozzi, Angelo; Varsano, Francesca

doi:10.1016/j.jallcom.2021.159202

Cited by 18 publications

(14 citation statements)

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“…The material synthesis was carried out similarly as previously reported [12,13]. Briefly, the elements (arsenic powder from Alfa Aesar, 99%, potassium cubes from Alfa Aesar, 99.5%, calcium granules from Sigma Aldrich, 99.5%, iron powder from Alfa Aesar, 99.998%, Barium rods from Alfa Aesar, 99+%, Na ingots from Alfa Aesar, 99.8%) were weighed and mixed in a 60 ml stainless steel grinding jar with five 12 mm steel balls in a ball to powder weight ratio of 30:1.…”

Section: Methodsmentioning

confidence: 99%

“…Briefly, the elements (arsenic powder from Alfa Aesar, 99%, potassium cubes from Alfa Aesar, 99.5%, calcium granules from Sigma Aldrich, 99.5%, iron powder from Alfa Aesar, 99.998%, Barium rods from Alfa Aesar, 99+%, Na ingots from Alfa Aesar, 99.8%) were weighed and mixed in a 60 ml stainless steel grinding jar with five 12 mm steel balls in a ball to powder weight ratio of 30:1. For all the samples, an excess in the A, AE and As content was introduced to counterbalance oxidation of the starting materials [13]. The pristine 1144 starting composition is thus Ca:K:Fe:As = 1.28:1.24:4:4.2.…”

Section: Methodsmentioning

confidence: 99%

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Tailoring the critical temperature of Ca/K-1144 superconductors: the effect of aliovalent substitution on tetragonality

Masi

Duchenko

Celentano

et al. 2022

Supercond. Sci. Technol.

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Among the Iron Based Superconductors (IBSC), the so-called 1144 family attracted in recent years significant interest due to its stoichiometric nature, with materials robust towards chemical inhomogeneities and characterized by a well-defined critical temperature. The most studied 1144 compounds are in fact characterized by the A1AE1Fe4As4 chemical composition, where A and AE constitute an appropriate combination of Alkaline and Alkaline-Earth metals, respectively. The 1144 structure is in fact formed only when the A and AE elements respect specific requirements in terms of relative size and parent compounds structure. The stoichiometric aspect, one of their strong points, has represented however up to today a restriction, limiting the conceptualization of 1144 structures to quaternary compounds. In this work, we demonstrate that to obtain the 1144 crystalline phase it may be sufficient to maintain a 1:1 ratio between ions of different size that intercalate the Fe-As planes, and that in selected conditions an opportunely tailored cation substitution is possible. Using a simple mechanochemically assisted synthesis route 1144 compounds where Ca is substituted by Na, K by Ba, and both simultaneously, are obtained. We demonstrate that the critical temperature of doped compounds is not simply related to the substitution amount or to the resulting Fe valence. We show that the superconducting transition is in fact linked to the structural distortion induced by the chemical composition variation: by tailoring the chemical composition we obtain doubly substituted samples - with substitution levels up to 20% - characterized by a tetragonality ratio c/a similar to the pristine compound and critical temperatures of approximately 34 K.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Tailoring the critical temperature of Ca/K-1144 superconductors: the effect of aliovalent substitution on tetragonality

Masi

Duchenko

Celentano

et al. 2022

Supercond. Sci. Technol.

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“…Briefly, elemental powders were subjected to a milling treatment using a steel vial and steel balls in a 30:1 ball to powder mass ratio for 5 h. The pressed powders were then subjected to thermal treatment for 10 h at 750 °C, adopting a 10 °C/min heating rate and a 5 °C/min cooling rate. With respect to our previous work, a slight imbalance in the starting Ca:K ratio was introduced in order to minimize K-122 phase segregation [ 17 ] starting thus from a nominal Ca:K:Fe:As = 1.2:1.18:3.75:4 atomic ratio. XRD diffraction patterns (data not shown) show the distinctive peaks of the p4/mmm 1144 phase [ 1 ] as in our previous work [ 17 ] and do not highlight significant presence of secondary phases (only traces of K-122 and CaO are evident).…”

Section: Methodsmentioning

confidence: 99%

“…With respect to our previous work, a slight imbalance in the starting Ca:K ratio was introduced in order to minimize K-122 phase segregation [ 17 ] starting thus from a nominal Ca:K:Fe:As = 1.2:1.18:3.75:4 atomic ratio. XRD diffraction patterns (data not shown) show the distinctive peaks of the p4/mmm 1144 phase [ 1 ] as in our previous work [ 17 ] and do not highlight significant presence of secondary phases (only traces of K-122 and CaO are evident). The sample has been characterized by means of DC magnetic measurements applied perpendicularly to the disk surface.…”

Section: Methodsmentioning

confidence: 99%

Critical Current and Pinning Features of a CaKFe4As4 Polycrystalline Sample

et al. 2021

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We analyze the magnetic behavior of a CaKFe4As4 polycrystalline sample fabricated by a mechanochemically assisted synthesis route. By means of DC magnetization (M) measurements as a function of the temperature (T) and DC magnetic field (H) we study its critical parameters and pinning features. The critical temperature Tc has been evaluated by M(T) curves performed in Zero Field Cooling-Field Cooling conditions. These curves show the presence of a little magnetic background for temperatures above Tc, as also confirmed by the hysteresis loops M(H). Starting from the M(H) curves, the critical current density Jc of the sample has been calculated as a function of the field at different temperatures in the framework of the Bean critical state model. The Jc(H) values are in line with the ones reported in the literature for this typology of samples. By analyzing the temperature dependence of the critical current density Jc(T) at different magnetic fields, it has been found that the sample is characterized by a strong type pinning regime. This sample peculiarity can open perspectives for future improvement in the fabrication of this material.

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“…CaNi-1144 经过 2 × 10 16 p/cm 2 的 3 MeV 质子辐照后 J c 明显提升，并且 J c 的各向异性显著减小，在低温下甚至接近各向同性 [63] 。CaCo-1144 受到剂量为 10 15 p/cm 2 的 3 MeV 质子辐照后 J c 性能也有着 2 倍的提升 [49] 有良好的化学稳定性。Masi 等人 [75] 采取了一种中低温(~600°C)烧结的合成方法，简化了制备过程。测试结果表明该方法制备的 CaK-1144 多晶样品中杂相较少，仅含有少量 K-122 及 FeAs 相，样品的 J c 性能较高，在 4.2 K 自场下约为 2 × 10 4 A/cm 2 ，但 T c 下降较大，约 30 K。Masi 等人 [76] 在此基础上进行了进一步的优化，通过改良球磨时的能量以及热处理过程，进一步将 J c 提高了 1.5 倍以上。 Pavan Kumar Naik 等人 [77] 研究了 Sn 对 CaK-1144 多晶样品性能的影响。在样品中，掺杂的 Sn 作为润湿相分布在晶界处，改善了晶粒的连接性，抑制二次相的形成，与 CaK-1144 之间保持化学稳定。研究表明，掺杂 30 wt% Sn 的多晶样品性能最高，在自场、4.2 K 下由 1.17 × 10 4 A/cm 2 (未掺杂)提升至 2.17 × 10 4 A/cm 2 。Ishida 等人 [78] 采用放电基超导多晶制备工艺的同时，还展开了 1144 线带材的研制工作。Cheng 等人 [24] 采用粉…”

Section: 单晶的生长unclassified