Effect of minor graphene doping on the microstructure and superconductivity of FeSe
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Effect of minor graphene doping on the microstructure and superconductivity of FeSe Chuangchuang Gong1 · Qian Zhao1,2 · Xuecheng Ping1 · Pan Zhang1 · Yishan Liu1 · Liang Hao1,2 Received: 25 May 2020 / Revised: 21 July 2020 / Accepted: 24 July 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract The polycrystalline FeSe bulks were sintered by solid-state reaction using a two-step sintering process to investigate the effect of graphene addition on the superconductivity and microstructure of the FeSe bulks. With the increase of graphene doping, the thickness of tetragonal β-FeSe sheet decreased obviously due to the existence of graphene between the layers. The grain connectivity of FeSe superconductor is significantly improved, and the critical transition temperature (Tc) is apparently enhanced up to 10.57 K in F e1.01SeG0.05, which increased by 15.3% compared to the F e1.01Se bulk without doping graphene. The critical current density (Jc) of Fe1.01SeG0.05 reaches 5 × 103 A/cm2 under zero magnetic field. Moreover, the critical current density (Jc) of Fe1.01SeG0.05 is simultaneously increased under high magnetic field due to the refined grains by graphene doping.
1 Introduction In recent years, iron-based HTS materials have attracted worldwide attention due to the superconducting transition temperature up to 55 K [1, 2]. Among them, the crystal structure of 11-series Fe-based superconductor is the simplest with a single tetrahedral structure forming by iron atom and element of the sixth main group (Se/Te), with the critical transition temperature of about 8 K [3]. The simple structure and the low toxicity of Se compared to As make the type of 11 superconductors very attractive for the study of superconductivity mechanism of iron-based superconductors and the possible practical applications. Furthermore, based on the superior characteristics of iron-based superconductors (IBSs), chemical doping is an effective method to improve superconductivity for the new
* Qian Zhao [email protected] * Xuecheng Ping [email protected] 1
Tianjin Key Laboratory of Integrated Design and On‑line Monitoring for Light Industry & Food Machinery and Mechanical Engineering, College of Mechanical Engineering, Tianjin University of Science and Technology, Tianjin 300222, China
Tianjin International Joint Research and Development Center of Low-Carbon Green Process Equipment, Tianjin 300222, China
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superconducting materials. Therefore, many research teams try to use different elements doping to replace Fe or Se sites in FeSe. Selenium has been successfully replaced by Te and S [4–6], and the results show that the method can significantly increase the superconducting transition temperature, such as the maximum initial transition temperature at FeSe0.5Te0.5 [7]. Meanwhile, many metal elements have been attempted to substitute the Fe site, including Mg, Al, Ti, V, Cr, Mn, Co, Nb, Cu, Zn, Mo, Sn, and Ag [8–13]. Among them, the doping of tetragonal structure metals such as Co, Ni, and Cu are conf
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