Processing of Manganese‐Doped [Bi 0.5 Na 0.5 ]TiO 3 Ferroelectrics: Reduction and Oxidation Reactions During Calcination and Sintering

The effect of multivalent manganese doping on the defect structure is studied for the “lead‐free” piezoelectric [Bi 0.5 Na 0.5 ]TiO 3 (BNT) by means of high‐frequency electron paramagnetic resonance (EPR) spectroscopy. The results show that manganese is incorporated with di‐ and trivalent oxidation states on a titanium site, acting as an acceptor (Mn ′ Ti , Mn ′′ Ti ). In particular, it is demonstrated that during calcination at 800°C the manganese functional centers are oxidized to Mn 3+ . Subsequent to the sintering at 1100°C, part of the trivalent manganese centers are reduced back to the initial Mn 2+ ‐oxidation state.