• Fujioka, Masaya

Abstract

<jats:sec><jats:label/><jats:p>Since the discovery of layered iron‐based LaFeAsO<jats:sub>1−<jats:italic>x</jats:italic></jats:sub>F<jats:sub><jats:italic>x</jats:italic></jats:sub>, a series of iron‐based superconductors has been reported. The five main types of iron‐based superconductors are 1111, 122, 111, 11, and 21113 systems. The name relates to the coefficients of the chemical formula. A notable point of iron‐based superconductors is that the conducting layers include iron elements, and it had been originally thought that ferromagnetic elements were unsuitable for superconductivity. In the Introduction, the history of superconductivity from the first superconductor, mercury, to the iron‐based superconductors is described. In the “Family of Iron‐Based Superconductor” section, the 1111, 122, 111, 11, and 21113 systems of superconductors are introduced. In particular, the effects of chemical doping and applied pressure on each type of iron‐based superconductor are explained in detail. In the section titled, “Relationship Between the Atomic Structure of Iron‐Based Superconductors and the Superconducting Transition Temperatures,” the relationship between the atomic structure of iron‐based superconductors and superconducting transition temperature is discussed. In this relationship, SmFeAsO<jats:sub>1−<jats:italic>x</jats:italic></jats:sub>F<jats:sub><jats:italic>x</jats:italic></jats:sub>has suitable conditions for obtaining a high superconducting transition temperature. Actually, it has the current record superconducting transition temperature of the iron‐based superconductors. In the section titled, “Detailed Superconducting Properties of Polycrystalline Sm‐1111,” the details of SmFeAsO<jats:sub>1−<jats:italic>x</jats:italic></jats:sub>F<jats:sub><jats:italic>x</jats:italic></jats:sub>are described from basic properties to wire fabrication. In this material, how to introduce a high level of fluorine into the oxygen sites is the most important factor in improving the superconducting transition temperature. Furthermore, the effect of metal addition has been observed by indium, lead, and tin. Each metal addition enhances each different superconducting property. By improving basic properties and discovery of new insights, the superconducting properties of wires and tapes are gradually improving toward practical use.</jats:p></jats:sec>

Topics

• impedance spectroscopy
• Oxygen
• layered
• iron
• size-exclusion chromatography
• tin
• wire
• Indium
• superconductivity
• superconductivity
• Mercury