Optimization of photostriction of BNT-based ceramics by forming phase boundary and tuning grain size

Ferroelectric materials with excellent photostrictive properties have attracted wide attention due to their great potential in optomechanical applications. Here, by doping Sr0.5Ba0.5(Co0.5Sb0.5)O3 into 0.75Na0.5Bi0.5TiO3-0.25K0.5Bi0.5TiO3, the band gap is effectively reduced (3.28–2.50 eV) and the morphological phase boundary (MPB) is formed. With the increase of sintering duration and doping amount, the grain size increases. Excellent photostriction (1.5×10−3) and photostriction efficiency (1.5×10−11 m3/W) were found in 0.98(Bi0.5(Na0.75K0.25)0.5TiO3-0.02Sr0.5Ba0.5(Co0.5Sb0.5)O3 ceramic. In the state of reduced bandgap, the significant enhancement in photostriction characteristics is mainly attributed to the increase in lattice susceptibility near MPB and a slight increase in grain size of the ceramics which effectively decreases the stress and subsequently reduces the total energy of the system. Raman spectra of variable laser power shows blue shift of the correlation modes, which indicates that the lattice shrinkage is dominated by distortion of BO6 octahedral.