2006 年 48 巻 1 号 p. 25-29
We review our recent works on the positional disorder and diffusion path of mobile ions in fast ionic conductors Bi1.4Yb0.6O3and La0.67Li0.16TiO3. These were studied through the nuclear density distribution obtained by a combined technique including the Rietveld refinement, the maximum-entropy method (MEM) and MEM-based pattern fitting of neutron powder diffraction data. The oxide ions in the fluorite-structured Bi1.4Yb0.6O3have a complicated disorder spreading over a wide area, shift to the ‹111› directions from the ideal fluorite position and diffuse along the ‹100› directions. At 77 K, the Li cations in the La0.62Li0.16TiO3perovskite are located at the 2csite (Wycoff notation of theCmmmspace group) on the (002) La deficient layer, while at room temperature, they spread over a wide area and migrate following the 2c-4f-2cor 2c-2d-2ctie line on the (002) layer.