Defects characterization of Dy-doped BaTiO3 ceramics via electron paramagnetic resonance

The point defects and the structural and dielectric properties of Dy-doped BaTiO3 ceramics prepared at 1400 °C were investigated. The solubility of Dy in the self-compensation mode was determined to be x = 0.07 for (Ba1−xDyx)(Ti1−xDyx)O3, and no EPR signals associated with the Dy3+ Kramers ion or the Ba and Ti vacancies were detected using the electron paramagnetic resonance (EPR) technique. As x increases, the dielectric behavior changed from a first-order phase transition to a diffuse phase transition to a Y7R dielectric-temperature stability. A strong EPR signal at g = 1.974, which is rare among rare-earth-doped BaTiO3 ceramics appeared unexpectedly in the single-phase (Ba1−xDyx)Ti1−x/4O3 ceramics with deliberately designed Ti vacancies. This signal was attributed to ionized Ba vacancy defects. A preference for the self-compensation mode of Dy3+ ions is responsible for the appearance of Ba vacancies. The real formula of the nominal (Ba1−xDyx)Ti1−x/4O3 is expressed as (Ba1−xDy3x/4)(Ti1−x/4Dyx/4)O3. In addition, the defect chemistry is discussed.