Energy storage performance of (K, Na)NbO ₃ ferroelectric thin films with Mn-Ta and Mn-Ti co-doping

The lead-free KNN (K _0.5 Na _0.5 NbO ₃ ) films were co-doped with Mn-Ta and Mn-Ti via the Sol-Gel method. With Mn doping, the leakage behavior in the KNN films is significantly weakened. Annealed at 700 °C, the KNNM film shows good crystallinity, dense morphology and better energy storage performance. With Mn-Ta and Mn-Ti co-doping, the KNNM4R (K _0.5 Na _0.5 Nb _0.96-x Mn _0.04 R _x O ₃ , R = Ta, Ti) films still show tetragonal phase and the smoothest surface morphology at 6mol% Ta or Ti content, with about 200 nm in thickness. Under the breakdown field strength of 2700 kV/cm and 2800 kV/cm, the (P _m -P _r ) of Ta6 and Ti6 films are 20.7 μC/cm ² and 22.4 μC/cm ² , the W _rec and η are up to 20.7 J/cm ³ , 23.9 J/cm ³ and 57%, respectively.