Strain-induced phase and oxygen-vacancy stability in ionic interfaces from first-principles calculations

Understanding interfacial chemistry is becoming crucial in materials design for heterointerfaces. Using density functional theory, we elucidate the effect of strained interfaces on phase and oxygen-vacancy stability for CeO₂|ZrO₂, ThO₂|ZrO₂ and CeO₂|ThO₂ interfaces. The calculations show that ZrO₂ transforms from cubic fluorite to the orthorhombic columbite under tensile strain providing evidence of a previous experimental speculation of an unrecognized ZrO₂ phase. We also show oxygen vacancy formation energy decreases in the presence of tensile strain. As a result, the interfacial strain could be used as a knob to stabilize oxygen vacancies on either side of the interface, and control their concentration for fast-ion conductor applications.