This work concerns the growth of (Bi0,5Na0,5)TiO3 on Si/SiO2/LNO by RF magnetron sputtering. We observed, for the first time on BNT thin films, reactions that destroy the film. This behavior is associated to sodium or sodium oxide segregation. After an extensive description of the sodium impact onto the film, a solution with adapted deposition conditions to suppress these effects is reported. Raising the sputter deposition temperature to 250 °C allows to have a pure perovskite BNT single phase. The ferroelectric, dielectric and piezoelectric properties of BNT films (thickness = 350 nm) were assessed. In particular, the macroscopic piezoelectric coefficient d33 attains a maximum value of 56 pm/V.