Chemical and structural origin of hole states in yttria-stabilized zirconia. (15th January 2021) - Dong, Yanhao
Abstract: Yttria-stabilized zirconia (YSZ) has important electrochemical applications as a fast oxygen ion conductor and is the state-of-the-art electrolyte material for solid oxide fuel/electrolyzer cells. While much attention has been paid to the fast oxygen ion conduction, the electronic conductivity and especially hole carriers are not well understood, yet essential for the electrochemical stability, conduction kinetics and microstructural evolution in YSZ. The present work uses first-principles calculations to illustrate the chemical nature and local structural features of hole states in oxidized YSZ. Three types of hole states have been identified, including delocalized hole states on normal oxygen ions, localized hole states on special oxygen ions with extreme local structures, and peroxide-like groups. The implications on various experimental observations are discussed. Graphical Abstract: Atomistic simulations are conducted to illustrate the chemical and structural origin of hole states in yttria-stabilized zirconia, which explains various experimental observations including enhanced conductivity, oxygen bubble formation and high migration energy of hole polarons. Image, graphical abstract