Preparation and characterization of a new graphite superconductor: Ca0.5Sr0.5C6

Saki Nishiyama, Hidenori Fujita, Masatoshi Hoshi, Xiao Miao, Takahiro Terao, Xiaofan Yang, Takafumi Miyazaki, Hidenori Goto, Tomoko Kagayama, Katsuya Shimizu, Hitoshi Yamaoka, Hirofumi Ishii, Yen Fa Liao, Yoshihiro Kubozono

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Abstract

We have produced a superconducting binary-elements intercalated graphite, CaxSr1-xCy, with the intercalation of Sr and Ca in highly-oriented pyrolytic graphite; the superconducting transition temperature, T c, was ~3 K. The superconducting CaxSr1-xCy sample was fabricated with the nominal x value of 0.8, i.e., Ca0.8Sr0.2Cy. Energy dispersive X-ray (EDX) spectroscopy provided the stoichiometry of Ca0.5(2)Sr0.5(2)Cy for this sample, and the X-ray powder diffraction (XRD) pattern showed that Ca0.5(2)Sr0.5(2)Cy took the SrC6-type hexagonal-structure rather than CaC6-type rhombohedral-structure. Consequently, the chemical formula of CaxSr1-xCy sample could be expressed as 'Ca0.5(2)Sr0.5(2)C6'. The XRD pattern of Ca0.5(2)Sr0.5(2)C6 was measured at 0-31 GPa, showing that the lattice shrank monotonically with increasing pressure up to 8.6 GPa, with the structural phase transition occurring above 8.6 GPa. The pressure dependence of T c was determined from the DC magnetic susceptibility and resistance up to 15 GPa, which exhibited a positive pressure dependence of T c up to 8.3 GPa, as in YbC6, SrC6, KC8, CaC6 and Ca0.6K0.4C8. The further application of pressure caused the rapid decrease of T c. In this study, the fabrication and superconducting properties of new binary-elements intercalated graphite, CaxSr1-xCy, are fully investigated, and suitable combinations of elements are suggested for binary-elements intercalated graphite.

Original languageEnglish
Article number7436
JournalScientific Reports
Volume7
Issue number1
DOIs
Publication statusPublished - Dec 1 2017

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    Nishiyama, S., Fujita, H., Hoshi, M., Miao, X., Terao, T., Yang, X., Miyazaki, T., Goto, H., Kagayama, T., Shimizu, K., Yamaoka, H., Ishii, H., Liao, Y. F., & Kubozono, Y. (2017). Preparation and characterization of a new graphite superconductor: Ca0.5Sr0.5C6. Scientific Reports, 7(1), [7436]. https://doi.org/10.1038/s41598-017-07763-y