Structure fluctuation in Gd- and Mg-substituted BaTiO3 with cubic structure

Abstract

Gd- and Mg-substituted barium titanate crystals (Ba1−xGdx)(Ti1−x/2Mgx/2)O3 with the Gd composition range of x > 0.1 show no ferroelectric phase transition. To discuss atomic thermal fluctuations in such unusual barium titanate crystals with cubic symmetry, accurate crystal structure analyses were performed by the maximum entropy method (MEM)/Rietveld method with the split-atom model and anharmonic temperature factor model using high-energy synchrotron radiation X-ray diffraction data. The off-centered positions of Gd ions at the Ba site in the probability density function were clearly observed at a low temperature but smeared in the high-temperature region by the over-barrier motion of Gd ions.