X-ray diffraction study for one-dimensional ionic conductors K x (Ga1 − y Aly)2 + x Ti2 − x O7 (x ≃ 0.14, y ≃ 0.10, 0.23, 0.39)

Abstract

The structures of one-dimensional ionic conductors K x (Ga1 − y Al y )2 + x Ti2 − x O7 (x ≃ 0.14, y ≃ 0.10, 0.23, 0.39) were refined by single-crystal X-ray diffraction. A one-dimensional tunnel-like space with a large cross section is formed by the linkage of coordination polyhedra of the metal and oxygen ions; K ions are distributed in the tunnel. Significant differences were seen in structures with different Al content; these differences could be explained by considerations in crystal chemistry. The probability density functions (PDFs) of the K ion were obtained using up to fourth-order terms of the atomic displacement parameters. The joint PDFs for the K ion have clarified that a K conduction path deviates slightly from the central axis of the tunnel in all the samples. In contrast with the usual one-dimensional ionic conductors, no distinct bottleneck effect was observed from the joint-PDFs and one-particle potentials.