“…On the other hand, the values of ε r and tan δ at 1 kHz are 411, 550, 702, 679, and 0.041, 0.027, 0.022, 0.026 for BNT thin film annealed at 600, 650, 700, and 750 °C, respectively, and with the increase of annealing temperature the variations of ε r and tan δ are as same as those of 2 P r and 2 P s , obviously. The increase of ε r values (600–700 °C) is induced by the grain size effect on dielectric properties of polycrystalline thin films, while the decrease of ε r values above 700 °C is due to the insufficient Bi supply which results in nonstoichiometric structural defects in the BNT thin films 23. The decrease of tan δ with the increase of annealing temperature (600–700 °C) is due to the mobile oxygen vacancy affected by the annealing temperature 24, while the tan δ increase above 700 °C may be due to the insufficient Bi supply.…”