Large photostriction near the phase boundary in BiFeO3 under varying epitaxial strain

Controlling the structure and properties of perovskite materials through various handles has always been an important research direction. In this present study, constrained density functional theory calculations are performed to systematically investigate the impact of illumination on the so-called R and the T phases of strained BiFeO₃ film under different epitaxial biaxial strains. We find that the phase transition strain boundary between the two phases is barely affected by illumination. However, it is discovered that light can induce a noticeable change in the two phases population, and that both the R and the T phases are strongly photostrictive near the phase transition boundary, with such photostriction being mainly accounted for by a converse piezoelectric model. The results of our calculations reveal the exciting prospect of using strained phases of BiFeO₃ for photostrictive applications. This combined with their known functional behavior could lead to devices with exotic cross functionality.