title: Formation of a solid solution between [N(C2H5)4][BF4] and [N(C2H5)4][PF6] in crystal and plastic crystal phases.
abstract: The phase behavior of [N2222][BF4] and [N2222][PF6] (N2222+= tetraethylammonium cation) binary systems has been investigated in the present study. Differential scanning calorimetry revealed that the crystal-to-plastic-crystal transition temperature decreases upon mixing the two salts, with a minimum at x([N2222][PF6]) = 0.4, where x([N2222][PF6]) denotes the molar fraction of [N2222][PF6]. Powder X-ray diffraction analysis indicated the formation of a solid solution with a rock-salt type structure in the plastic crystal phase at all ratios and the lattice parameter a changes according to Vegard's law. In the crystal phase, two solid solution phases based on the structures of the single salts are observed. Raman spectroscopy confirmed the changes in the solid-solid transition temperature as observed by differential scanning calorimetry. Consequently, in the resulting phase diagram, the solid solution is formed in a wide x([N2222][PF6]) range for both the crystal and plastic crystal phases.
authors.affiliation: Department of Fundamental Energy Science, Graduate School of Energy Science, Kyoto University Sakyo-ku, Kyoto 606-8501, Japan. k-matsumoto@energy.kyoto-u.ac.jp.
authors.forename: Kazuhiko
authors.identifier: http://orcid.org/0000-0002-0770-9210
authors.initials: K
authors.lastname: Matsumoto
authors.affiliation: Department of Fundamental Energy Science, Graduate School of Energy Science, Kyoto University Sakyo-ku, Kyoto 606-8501, Japan. k-matsumoto@energy.kyoto-u.ac.jp.
authors.forename: Ryojun
authors.initials: R
authors.lastname: Nonaka
authors.affiliation: Department of Fundamental Energy Science, Graduate School of Energy Science, Kyoto University Sakyo-ku, Kyoto 606-8501, Japan. k-matsumoto@energy.kyoto-u.ac.jp.
authors.forename: Yushen
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Fundamental Energy Science, Graduate School of Energy Science, Kyoto University Sakyo-ku, Kyoto 606-8501, Japan. k-matsumoto@energy.kyoto-u.ac.jp.
authors.forename: Gleb
authors.initials: G
authors.lastname: Veryasov
authors.affiliation: Department of Fundamental Energy Science, Graduate School of Energy Science, Kyoto University Sakyo-ku, Kyoto 606-8501, Japan. k-matsumoto@energy.kyoto-u.ac.jp.
authors.forename: Rika
authors.initials: R
authors.lastname: Hagiwara