Facet-Dependent Ba Dissolution of Tetragonal BaTiO3 Single Crystal Surfaces

Tetragonal BaTiO3 with a high dielectric property is used as the principal material for multilayer ceramic capacitors (MLCCs), a core component of state-of-the-art electronic devices. However, Ba2+ at BaTiO3 surfaces can be dissolved in aqueous-based media, and such chemical instability has been a major obstacle to environmentally friendly aqueous-based MLCC processes. To understand the behavior of Ba2+ dissolution, we investigated H2O(l) and (H+ + Cl-)(aq.) adsorption on the single crystal surfaces of BaTiO3(100), (111), and (110) using density functional theory calculations. We found that the onset pH for Ba2+ dissolution is 1.65, 2.46, and 3.18 for BaTiO3(100), (111), and (110), respectively, indicating that the thermodynamics of Ba2+ dissolution are facet dependent. The onset pH and the coordination number (CN) of Ba on each surface shows a linear correlation, suggesting that the CN of Ba is a critical factor that can predict the Ba2+ dissolution thermodynamics.