Defect engineering in Ba-doped SrTiO3 ball-milled particles

• The properties of Ba-doped SrTiO 3 materials obtained through the ball milling process can be tuned by heat treatment. • Changes in the optical and magnetic properties are linked to defect evolution and the removal of chemisorbed water. • The decrease in magnetic saturation correlates with the reduction in the size of vacancy aggregates on the surface, as well as their number. Owing to their unusual optical and electrical properties, nanocrystalline SrTiO 3 has sparked great interest in optoelectrical and photocatalytic devices. However, the relationship between the structure of SrTiO 3 and its resulting properties remains poorly understood, thus limiting property-oriented material design, especially in the case of large-scale top-down manufacturing, such as ball milling. Here, we employed multiple characterization techniques, such as X-ray photoelectron spectroscopy, positron annihilation spectroscopy, X-ray diffraction, and SEM imagining, to explain the optical and magnetic properties of Ba-doped SrTiO 3 in light of its structural and compositional features, including surface groups and defect sites. The experimental data showed that the properties of SrTiO 3 materials obtained through the ball milling process can be easily tuned by heat treatment in an appropriate atmosphere. The powders produced have numerous defects and feature weak room-temperature ferromagnetism unrelated to the Ti 3+ state. Changes in the optical and magnetic properties are linked to defect evolution and the removal of chemisorbed water. Isolated oxygen vacancies cause the appearance of an intense red band at 615 nm but do not strongly affect the magnetic properties. The decrease in magnetic saturation correlates with the reduction in the size of vacancy aggregates on the surface, as well as their number.