Erünal, E.E.ErünalJakes, P.P.JakesKörbel, S.S.KörbelAcker, J.J.AckerKungl, H.H.KunglElsässer, C.C.ElsässerHoffmann, M.J.M.J.HoffmannEichel, R.A.R.A.Eichel2022-03-042022-03-042011https://publica.fraunhofer.de/handle/publica/22705510.1103/PhysRevB.84.184113The interplay between aliovalent CuO doping and nonstoichiometry on the development of defect structures and the formation of secondary phases of antiferroelectric NaNbO(3) ceramics has been investigated by means of x-ray diffraction (XRD), first-principles calculations using density functional theory (DFT), and electron paramagnetic resonance spectroscopy. The results indicate that, for stoichiometric 0.25 mol% CuO-doped NaNbO(3), as well as for 2.0 mol% Nb-excess sodium niobate, the Cu(2+) functional centers are incorporated at the Nb site (Cu'''(Nb)). For reasons of charge compensation, two kinds of mutually compensating defect complexes (Cu'''(Nb) - V(O)(center dot center dot))' and (V(O)(center dot center dot) - Cu(Nb)(center dot center dot) - V(O)(center dot center dot))(center dot) are formed where, for the niobium-excess compound, additionally, V'(Na) contribute to the mechanism of charge compensation. In contrast, for 2.0 mol% Na-excess sodium niobate, a Na(3)NbO(4) secondary phase has been detected by XRD, and only part of the Cu(2+) forms these types of defect complexes. The major part of the Cu(2+) is incorporated in a fundamentally different way by forming Cu(2+)-Cu(2+) dimeric defect complexes.enpoint defectmodeltheorycrystal defectdielectric deviceferroelectric devicepiezoelectric device620530journal article