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The defect energetics for several dopant incorporation modes and the dielectric–electric properties in Er‐doped BaTiO3 were studied by numerical simulations and the dielectric modulus formalism. Two “mixed” incorporation modes, both compatible with the existence of oxygen vacancies, are proposed. Simulation results for the solution energies show that, despite self‐compensation is the most favourable mode, the mixed modes exhibit quite similar energies and, therefore, could be active under some conditions. The incorporation of Er3+ into the BaTiO3 lattice decreases the dc conductivities with respect to the undoped case at high temperatures. Molecular Dynamics calculations and experimental measurements about conducting properties of Er‐doped BaTiO3 allow one to calculate activation energies for ionic conductivity, which agree with data for oxygen migration. Experimental and Molecular Dynamics data are then correlated with the possible defect configurations. Scheme of the defect clusters corresponding to the proposed mixed incorporation mechanisms: (a) “Ti‐vac” and (b) “Ba‐vac”. Green, grey, blue, and red balls correspond, respectively, to Ba2+, Ti4+, Er3+, and O2− ions.

a b s t r a c tIn this work the dielectric behaviour and main features of the phase transition of BaTiO 3 and Ba 0.99 Er 0.01 TiO 3 ceramics were carefully investigated. The temperature and frequency dependences of the dielectric properties of erbium doped BaTiO 3 ceramics were measured in the 25-225 • C and 100 Hz to 10 MHz ranges, respectively. From this study, a dielectric anomaly in the ferroelectric-paraelectric phase transition of the Ba 0.99 Er 0.01 TiO 3 ceramic was observed. The features of the samples phase transition were analysed by using Curie-Weiss, Santos-Eiras' and order parameter local phenomenological models. In the BaTiO 3 system, all models showed a normal phase transition, while was not possible to establish the character of the phase transition in the Ba 0.99 Er 0.01 TiO 3 system. The relaxation parameters of conductive processes for the study ferroelectric materials, analysed in the time domain, did not show any influence on the ferroelectric-paraelectric phase transition. Finally, it was demonstrated that the anomaly observed on the phase transition of the erbium doped BaTiO 3 ceramics is associated with the processes that results in the PTCR effect.

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