Defect profile and electrical properties of Nb2O5-doped BaTiO3 materials

This work deals with the changes in properties induced by the incorporation of donor ions into the BaTiO3 lattice. We focused on the relationship between microstructual developmnt and the defect profile of Nb-based compositions around the semiconducting-insulating transition at 0.3% of donor oxide. The results indicated that the defect structure that developed controlled both microstructural and electrical properties. On sintering slightly doped BaTiO3, large semiconducting grains and low barium vacancy concentration were detected. This behavior was explained by considering an electronic compensation mechanism based on dopant incorporation. Further dopant addition led to a dramatic grain-growth inhibition and a clear transition to a material with higher resistivity. In addition, an extraordinary generation of barium vacancies was observed. Heavily doped materials consisted of core-shell structures with a Ti-rich phase surrounding BaTiO3 grains. This phenomenon originated a significant grain-boundary barrier layer response. (C) 2003 Kluwer Academic Publishers.