Notable enlargement of remnant polarization for fatigue-free SrBi₄Ti₄O₁₅ thin films by La-substitution

La-doped SrBi4Ti4O15, SrBi4-x La (x) Ti4O15 (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 (2P(r) = 46 mu C/cm(2)). Meanwhile, the SBLT-0.10 film shows little change of P-nv and -P-nv up to 4.4 x 10(10) switching cycles, suggesting an excellent fatigue-endurance characteristics.