Donor-acceptor charge complex formation in barium titanate ceramics

BaTiO3 ceramics containing Mn accepters and Mo(6+), W(6+) and Nb(5+) on B-sites have been fired in reducing atmosphere and thereafter re-oxidized in N(2)/O(2). In single Mn-doped ceramics a valence change from Mn(2+) to Mn(3+) was observed for oxygen partial pressures of 5Pa and T>600 degrees C. Valence changes have been detected using dielectric, and thermomechanical measurements. Charge compensation and complex formation between accepters and donors strongly stabilize the divalent Mn accepters ions in BaTiO(3).