High‐recoverable energy‐storage density and dielectric tunability in Eu3+‐doped NBT‐xSTO binary solid solution films

The Eu3+-doped (1 - x)Na0.5Bi0.5TiO3-xSrTiO(3) (Eu-NBT-xSTO) thin films were prepared on Pt/Ti/SiO2/Si substrates. Raman analysis reveals that the phase structure may undergo a phase evolution of rhombohedral -> rhombohedral + tetragonal (morphotropic phase boundary) -> tetragonal with increasing content of STO. The scanning electron microscopy images show that the uniformity and high density of Eu-NBT-xSTO films were increased by adding STO, resulting in a pronounced effect on energy storage properties. The e-T curves confirm that a high phase transition diffuseness of gamma = 2.02 +/- 0.03 and 1.98 +/- 0.03 was achieved in Eu-NBT-0.24STO and Eu-NBT-0.3STO films, respectively. Furthermore, a large recoverable energy storage density of 31.5 J cm(-3) with an efficiency of 64% was obtained in Eu-NBT-0.3STO film, which also exhibited good thermal stability in the temperature range between -60 degrees C and 80 degrees C as well as long-term stability up to 1 x 10(8) switching cycles. These results suggest that the Eu-NBT-xSTO films may be used in the novel and advanced energy storage capacitors.