Impact of Aliovalent Alkaline-Earth metal solutes on Ceria Grain Boundaries: A density functional theory study

Ceria has proven to be an excellent ion-transport and ion-exchange material when used in polycrystalline form with a high-concentration of aliovalent doped cations. Despite its widespread application, the impact atomic-scale defects this are scarcely studied poorly understood. In article, using first-principles simulations, we provide fundamental understanding atomic-structure, thermodynamic stability electronic properties undoped grain-boundaries (GBs) alkaline-earth metal (AEM) GBs ceria. Using density-functional theory GGA+U functional, find $\Sigma$3 (111)/[$\bar{1}$01] GB is thermodynamically more stable than (121)/[$\bar{1}$01] due larger atomic coherency plane. We dope $\sim$20% [M]$_{GB}$ (M=Be, Mg, Ca, Sr, Ba) that energies have parabolic dependence on size solutes, interfacial strain packing density GB. see stabilization upon Sr Ba doping whereas Be Mg render them unstable. The states reveal no defect present or above band gap AEM ceria, which highly conducive maintain low mobility ionic conductor. properties, unlike stability, exhibit complex inter-dependence structure chemistry host solutes. This work makes advances cation ceria serving as anchor future studies can focus improving ionic-transport.