Tunable dielectric and energy storage properties in nonstoichiometric NaNbO3 thin films

Abstract

Defect engineering is an essential strategy to achieve the tunable functionalities in perovskite oxides containing volatile elements. In this work, we reported the influence of sodium deviation on the structural and electrical properties of sol-gel-derived NaNbO3 (NNO) thin films. Sodium deviation in NNO thin films was controlled by the level of x = Na/Nb ratio (x = 0.90, 1.00, 1.10, and 1.20) in the precursor solution. It is found that sodium deviation in NNO thin films has little influence on the crystalline structure, but the dielectric, leakage current, and energy-storage properties are closely related to the sodium deviation. Although excess sodium (i.e., x = 1.10) in the precursor solution could improve the leakage current and dielectric loss, the large polarization and superior energy storage density are observed in sodium-deficient (i.e., x = 0.90) NNO thin film. These results indicate sodium deviation as a valuable tool to balance the targeted properties of sodium-based perovskite oxides for potential applications.