Particle size effect on the microstructure and the aging process of flash-sintered barium titanate from micro and nanopowders

Flash sintering is a novel sintering technique that allows high-density ceramics to be obtained at low temperatures and using short dwell times, thus providing an energy-efficient alternative to conventional sintering. The microstructure of flash-sintered samples can be fine-tuned by a proper control of electrical parameters such as current density, electric field, and current profile, yielding significant improvements of functional properties. The starting powder should also be carefully selected since better sintering results are reported for smaller green grain sizes. However, this work evidences time evolution of electrical properties of flash-sintered BaTiO3 ceramics from submicron powders. The results reveal that these transformations greatly depend on powder grain size and can be further adjusted with an adequate selection of electric power profiles. This work provides new insights into ongoing phenomena during field-assisted sintering, such as grain growth and defect formation dynamics. Although the results focus on BaTiO3, it offers a new pathway to tailor the microstructure of flash-sintered ceramics, which may be extended to other electronic materials. Flash sintering experiments on different-sized BTO powders are performed, and the influence of the conditions over the achieved microstructures and functional properties is shown. For smaller powder sizes a time instability of properties is revealed.