Effect of Nanosized FeF2 Addition on Phase Formation, Microstructure and Critical Temperature of Tl2Ba2CaCu2O8 Superconductor

Y.S. Ng, D. E. Uskenbaev, Serua Tursyntay, Maxim Kulakov, Yessenboldy Khuanbay, W. Kong, M. N.Mohd Nasir, A. B. P. Ilhamsyah

2026

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DOI 10.66514/ssst34-1-31-39
Data confidence 70 medium
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Abstract

The Tl2Ba2CaCu2O8 (Tl-2212) phase superconductor with critical temperature 110 K, offers a better phase stability, easier synthesis control and more reproducible superconducting properties than Tl2Ba2Ca2Cu3O10 (Tl-2223) with critical temperature 125 K, making it more suitable for systematic studies despite its slightly lower critical temperature. To enhance the critical current density, magnetic nanoparticles with size, l between the coherence length,  and the penetration depth,  can be added to the Tl-2212 phase, where the particles act as effective flux pinning centers. In this study, 120 nm antiferromagnetic FeF2 nanoparticles were added into Tl2Ba2Ca2Cu2O8(FeF2)x with x = 0 to 0.04 wt.%. The main aim was to investigate the effects of nanosized FeF2 on the Tl-2212 phase formation and critical temperature. X-ray diffraction (XRD) analysis confirmed that a single Tl-2212 superconducting phase was formed in all FeF2 added samples. The non-added sample exhibited a superconducting onset critical temperature (Tc-onset) of 108 K, whereas samples with FeF2 additions of x ≤ 0.03 wt. % retained a relatively high Tc-onset of approximately 100 K, indicating that low FeF2 concentrations have only a minimal effect on the onset of superconductivity. These results demonstrate that FeF2 can be incorporated into Tl-2212 without causing significant disruption to phase formation or the critical temperature provided that the doping level is x ≤ 0.03 wt.%. This suggests that careful FeF2 doping could be a viable addition for optimizing microstructural and textural properties while maintaining high critical temperature.