First-principles investigation of phosphate ester and carboxylic acid on BaTiO3 surfaces with stoichiometric terminations

Phosphate ester and carboxylic acid are common anchoring groups for organic dispersants which are used in BaTiO3 suspension processes for multi-layered ceramic capacitors (MLCCs). However, the adsorption behaviors and the structure sensitivity of phosphate ester and carboxylic acid on BaTiO3 surfaces at the molecular-level remain largely unknown and thus require a systematic study. In this report, we theoretically investigate ad-sorption of those molecules on the BaTiO3 surfaces using Density Functional Theory (DFT). Our study includes three low-index facets of BaTiO3: the BaTiO3(001), (011), and (111) surfaces with the stoichiometric terminations. Also, to model phosphate ester and carboxylic acid, we employ methyl dihydrogen phosphate (CH3OPO3H2) and acetic acid (CH3COOH) in our simulation. Our DFT result reveals that BaTiO3(011)-BaTiO is the most active surface for molecular and dissociative adsorption of phosphate ester and carboxylic acid compared to other surfaces. Also, the saturated coverages of phosphate ester and carboxylic acid on the BaTiO3(011)BaTiO surface are 0.5 ML (monolayer), respectively, based on the grand potential analysis. These findings reveal the role of the BaTiO3 facets and terminations for adsorption of phosphate ester and carboxylic acid. Thus, we believe that our DFT result will be a building block for understanding on the interaction of tetragonal BaTiO3 with relevant dispersants which are utilized in MLCC applications.