Effects of Y Doping on Dielectric and Varistor Properties of CaCu3Ti4O12 Thin Films
Ca1−3x/2YxCu3Ti4O12 (x = 0, 0.05, 0.1, 0.15, and 0.2) (CCTO) thin films were prepared by a modified sol–gel method. The effects of Y doping on the microstructure and electrical properties of the CCTO thin films were investigated. According to x-ray diffraction analysis, the main phase of all Y-doped CCTO thin films is cubic Im3¯\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \bar{3} $$\end{document}. Meanwhile, some secondary phases were defected. Scanning electron microscopy analysis showed that Y doping can easily lead to a smaller grain size and larger porosity in CCTO thin films. Room-temperature dielectric analysis showed that the dielectric constant of different Y doping samples at 1 kHz was 4213, 4523, 4974, 4824, and 4777, and the dielectric losses were 0.053, 0.051, 0.062, 0.067, and 0.049, respectively. The study of Y-doped CCTO thin films showed that Y doping increased the dielectric constant of the films at low frequencies, but at the same time it increased their dielectric loss and decreased their dielectric frequency and temperature stability range. Y-doping had little effect on the nonlinearity of the films and did not significantly change their nonlinear coefficients.