Interactions between Mn dopant and oxygen vacancy for insulation performance of BaTiO3

We performed first-principles calculations and electron spin resonance (ESR) measurements on Mn-doped perovskite BaTiO3 (BT) ceramics in order to investigate the interactions between Mn dopant and O vacancy (V-O). We discovered the following two. First, V(O)s are stabilized at the nearest neighbor O site of Mn at a Ti site and this results in the suppression of V-O diffusion. Second, electrons generated by the formation of V(O)s are trapped in unoccupied Mn-3d orbitals in the BT bandgap. This indicates that the valence state of Mn changes according to the V-O density. We synthesized Mn-doped BT by varying the partial pressure of O-2 gas and examined the Mn valence states with ESR measurements. We successfully observed that the majority type of Mn ions (2+, 3+, and 4+) depends on O-2 gas pressure of the firing atmosphere. According to these theoretical and experimental investigations, we concluded that Mn dopants have two effects, i.e., V-O and electron carrier trapping. Moreover, the mechanisms of Mn doping in BT improved the insulation resistance, and the reliability of BT-based ceramic capacitors/condensers were thoroughly examined. Published by AIP Publishing.