Phase-Separation Control of K^sub x^Fe^sub 2-y^Se^sub 2^ Superconductor through Rapid-Quenching Process

• Published in: Journal of the Physical Society of Japan Vol. 86; no. 4; p. 305
• Main Authors: Yanagisawa, Yusuke, Tanaka, Masashi, Yamashita, Aichi, Suzuki, Kouji, Hara, Hiroshi, ElMassalami, Mohammed, Takeya, Hiroyuki, Takano, Yoshihiko
• Format: Journal Article
• Language: English
• Published: Tokyo The Physical Society of Japan 01-04-2017
• Subjects: Iron; Microstructure; Phase transitions; Quenching; Rapid quenching (metallurgy); Superconductors
• ISSN: 0031-9015; 1347-4073

K^sub x^Fe^sub 2-y^Se^sub 2^ exhibits iron-vacancy ordering at Ts ~ 270 °C and separates into two phases: a minor superconducting (iron-vacancy-disordered) phase and a major non-superconducting (iron-vacancy-ordered) phase. The microstructural and superconducting properties of this intermixture can be tuned by an appropriate control of the quenching process through T^sub s^. A faster quenching rate leads to a finer microstructure and a suppression of formation of the non-superconducting phase by up to 50%. Nevertheless, such a faster cooling rate induces a monotonic reduction in the superconducting transition temperature (from 30.7 to 26.0 K) and, simultaneously, a decrease in the iron content within the superconducting phase such that the compositional ratio changed from K^sub 0.35^Fe^sub 1.83^Se^sub 2^ to K^sub 0.58^Fe^sub 1.71^Se^sub 2^.