Excellent dielectric performance and nonlinear electrical behaviors of Zr-doped CaCu3Ti4O12 thin films

Abstract

The dielectric and nonlinear current–voltage properties of CaCu3Ti4−xZr x O12 (x = 0, 0.05, 0.1, 0.15 and 0.2) thin films prepared by the modified sol–gel method and annealed at 750 °C for 1 h were systematically studied. Zr doping resulted in a significant reduction in the mean grain size from 177.4 to 42.9 nm. The dielectric properties of the thin films increased significantly with the increase of Zr content from x = 0 to 0.2, indicating the importance of microstructure in controlling the dielectric properties of CaCu3Ti4−xZr x O12 thin films. A highly frequency-independent giant dielectric permittivity from 102 to 106 Hz was successfully achieved in CaCu3Ti3.8Zr0.2O12 thin film, which possessed a very high dielectric permittivity value of 7591 and a very low tanδ value of 0.023 at 1 kHz. The results indicated that reduction in the mean grain size affected the number of polarized ions per unit volume n0 (to improve e′) and the number of grain boundaries (to reduce tanδ). CaCu3Ti3.75Zr0.15O12 thin film showed the highest nonlinear coefficient (5.8) and lowest leakage current (131 μA). In addition, the relaxation mechanism based on the internal barrier layer capacitance model and the back-to-back dual Schottky barrier model were used to explain the dielectric properties and the nonlinear electrical behaviors of the samples.