Large visible-light-driven photostriction in Bi(Ni2/3Nb1/3)O3–PbTiO3 ferroelectrics

Photostrictive effect that has been discovered for over half a century is getting renewed interest in recent years in view of the great potentials for optomechanical applications. Ferroelectric materials represented by lead lanthanum zirconated titanate have been widely studied in this field because of their relatively large photostriction and fast photoresponse, but their wide bandgaps with limit response to visible light hinder further practical application. Here, visible-light-driven photostrictions of the order of 10 −3 are discovered in Bi(Ni 2/3 Nb 1/3 )O 3 –PbTiO 3 (BNNPT) ferroelectric solid solutions. Three BNNPT compositions with different phase structures, exhibiting notably different piezoelectric and photovoltaic properties, are selected to conduct the photostriction investigation, and their analogous photostrictive behaviors contradict with previous acknowledgment that the photostriction of ferroelectrics originates from the photovoltage-induced inverse piezoresponse. The nonuniform shifts of the XRD diffraction peaks under external laser illumination and the redshifts of the laser power dependent Raman modes disclose that the photostriction is mainly attributed to the light-induced distortion of BO 6 octahedra. This study sheds insight into the mechanism of the photostriction of ferroelectrics.