Theoretical modeling of defect segregation and space-charge formation in the BaZrO3 (210)[001] tilt grain boundary

• We study the BaZrO3 (210)[001] tilt grain boundary using density functional theory.
• Both protons and oxygen vacancies segregate with energy of − 1.32 eV and − 1.45 eV.
• We apply a space-charge model to the obtained segregation energies.
• Space-charge potentials of about 0.65 V are obtained for T < 900 K at wet conditions.
• The excess core charge is only due to protons when T < 900 K.

Density-functional theory (DFT) has been used to determine the structure and interface energy of different rigid body translations (RBTs) of the (210)[001] grain boundary (GB) in BaZrO3. There exist several different stable structures with almost equally low interfacial energy. Segregation energies of protons and oxygen vacancies have been determined for the most stable (210)[001] grain boundary structure. The results suggest that both defect species favor segregation to the same site at the boundary interface with minimum segregation energies of − 1.45 eV and − 1.32 eV for vacancies and protons respectively. The segregation energies have been used in a thermodynamic space-charge model to obtain equilibrium defect concentrations and space-charge potentials at a 10% dopant concentration. Space-charge potential barriers around 0.65 V were obtained at intermediate temperatures under hydrated conditions, where protons are the main contributor to the excess core charge. The potential is slightly lower under dry conditions.