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K
H(SeO
)
Kiyanagi, Ryoji; Matsuo, Yasumitsu*; Ohara, Takashi; Kawasaki, Takuro; Oikawa, Kenichi; Kaneko, Koji; Tamura, Itaru; Hanashima, Takayasu*; Munakata, Koji*; Nakao, Akiko*; et al.
no journal, ,
The materials, M
H(XO) (M=alkaline metal, X=Se, S), exhibit high protonic conductivities in a relatively low temperature region. The high protonic conductivities emerge upon a structural phase transition and the phase transition temperature (Tc) varies depending on the elements of M and X. In this study, mixed materials, RbKH(SeO), were studied by means of conductivity measurements and single crystal neutron structure analyses in order to clarify how the elements at the M site affect the Tc from the structural aspect. The conductivity measurements revealed that the Tc decreased as the K content increased. The variation of the Tc was found to be non-linear with respect to the K content. The structure analyses showed that the K ions preferred to occupy one of two M sites and the occupancy of the K ion at this site non-linearly varied. In addition, the SeO tetrahedron became more distorted as the K content increased, suggesting the close relationship between the distortion and the Tc.
H(SeO)Kiyanagi, Ryoji; Matsuo, Yasumitsu*; Ishikawa, Yoshihisa*; Noda, Yukio*; Ohara, Takashi; Kawasaki, Takuro; Oikawa, Kenichi; Kaneko, Koji; Tamura, Itaru; Hanashima, Takayasu*; et al.
no journal, ,
The materials represented as MH(XO) (M=alkali metals, X=Se, S) are known to exhibit high protonic conductivities at relatively low temperature. Although the high protonic conductivity is considered to be due to the disorder of the hydrogen bonds in the materials, details have not been well understood. In addition, clarification of the phase transition to the high proton conducting phase is important in order to understand the realization of the high protonic conductivity. In this study, a high temperature neutron structural study was carried out on RbH(SeO), and the solid solution of RbKH(SeO) were also investigated by means of conductivity measurements and neutron structural studies. The high temperature neutron structure analyses revealed that the protons in the high proton conducting phase were two dimensionally distributed, which is considered to be the direct observation of the conducting protons. The solid solution exhibited non-linear decreases of the phase transition temperatures as the K concentration increased. The K ions were found to prefer to occupy one of two possible sites, of which occupancies apparently have close relationship with the phase transition temperature.