A ferroelectric Bi4-xLaxTi3O12 (BLT) thin film library was fabricated from Bi2O3/La2O3/TiO2 multilayers using a multitarget RF-sputtering system equipped with an automated shutter. The polarization -electric field and structure were mapped as a function of the La content from x = 0 to 1. Remnant polarization (P,) increased as the La content decreased, and it reached a maximum 2P(r) of 20,mu C/cm(2) at x = 0.28. At x < 0.28 2P(r) decreased gradually as the La content decreased. This compositional dependence of the remanent polarization was the result of the degree of TiO6 tilting along the a-b plane changing as a function of the La content. This was quantitatively related to the intensity ratio between the (117) peak and the (008) peak in the X-ray diffraction (XRD) pattern and to the intensity of the Raman band at 848 cm(-1), arising from stretching mode of TiO6 octahedrons.