Notable enlargement of remnant polarization for fatigue-free SrBi 4 Ti 4 O 15 thin films by La-substitution

La-doped SrBi 4 Ti 4 O 15 , SrBi 4– x La x Ti 4 O 15 (SBLT- x , x = 0.00, 0.10 and 0.25), thin films have been successfully prepared by the sol–gel method. Structures, surface morphology and ferroelectric properties were investigated. Compared with undoped SBTi, SBLT-0.10 shows a notable larger remnant polarization (2 P r = 46 μ C/cm 2 ). Meanwhile, the SBLT-0.10 film shows little change of P nv and − P nv up to 4.4 × 10 10 switching cycles, suggesting an excellent fatigue-endurance characteristics.