Constructing polymorphic phase boundary for high-performance inorganic photostrictive materials

By converting light into mechanical strain, photostrictive materials are expected to define a revolutionary solution to the wireless micro-electromechanical devices. However, the photoinduced strain (photostriction) of most inorganic materials are unsatisfactory as compared to the electric-field-induced strain of ferro/piezoelectric materials. Here, we demonstrate the effective optimization of the photostriction of inorganic materials by constructing polymorphic phase boundary (PPB) in Pb₃V_2-xP_xO₈ compounds. Large photostriction over 0.3% and excellent photostrictive efficiency in the level of 10^-10 m³/W are realized in Pb₃V_2-xP_xO₈ compositions at the PPB region, which perform better than most of the existing inorganic photostrictive materials. Besides, photostriction over 0.1% (same level of piezoelectric strain) can be achieved with light intensity as low as 200 mW/cm². We theoretically reveal that enhanced photostriction arises from photoinduced phase transition driven by Pb-O-V collinearity and V-V dimer formation, and P-doping can facilitate the transition, enabling large deformation at low photoexcitation. This work will accelerate the development of high-performance inorganic photostrictive materials and their applications for optomechanical devices.