Theoretical prediction on interfacial bonding and strengthening mechanism of polymorphic ZrO₂/Fe interfaces

This work presents a theoretical way to reveal the strengthening mechanism of the activation of elements in the interface of polymorphic ZrO₂/Fe interfaces. O-terminated t-ZrO₂(001)/Fe(001) interface with site 3 atomic structure gives the largest W_ad than other interfaces, indicating its strongest interfacial binding strength. For O-terminated t-ZrO₂(001) slabs, the work of adhesion of t-ZrO₂/Fe interfaces decreases with the sequence of: site 3 (HCP) > site 1 (Top) > site 2 (Bridge), which implies the HCP sites occupy the strongest interfacial binding character. m-ZrO₂(101)/Fe(112) interfaces show small W_ad indicating their weak binding strength. Griffith's theoretical calculation predicts that the crack may initiate inside the bulk phases rather than at the interface for t-ZrO₂(001)_O2/Fe(001) site 3 interface; the interfacial binding strength of which is much higher than that of ZrO₂ or Fe bulk phases. The Ti-doped t-ZrO₂(001)_O2/Fe(001) has the highest interfacial binding strength, because the overlap population of Ti-O bonds in Ti-doped interface is as high as 0.41, and the overall interfacial atomic structure has been re-constructed after geometrical optimization. The lowest segregation energy (∼-0.1 eV) of Ti-doped t-ZrO₂(001)_O2/Fe(001) is given indicating the process of Ti dopant segregated into the interface is an exothermic reaction.