Structural study of Ca doped barium titanate

Both the combined structural refinement and the geometry energy calculation based on quantum mechanics were applied to determine the site preference and occupancies of Ca atom as a dopant in Ca-doped BaTiO3 prepared by the hydrothermal process. Of possible models based on cation disorder and anion vacancy, the best structural refinement result was obtained from the model, in which Ca atoms co-substituted for Ba and Ti atoms, and vacancies of the two O sites were created for charge compensation due to the substitution of Ca2+ ions for Ti4+ ions. The model proposed by the combined structural refinement was verified by the virtual crystal approximation method dealing with the disorder of atoms based on the first principle calculation. The final weighted R-factor and the goodness-of-fit for both data was 6.78% and 1.42%. The occupancies of Ca atoms distributed over Ba and Ti sites were 0.086(2) at Ba site and 0.027(2) at Ti site, and the vacancies of O atoms at O(1) and O(2) sites were 0.011(2) and 0.019(2), respectively. (C) 2011 Elsevier B.V. All rights reserved.