Dielectric properties of Al2O3 modified CaCu3Ti4O12 ceramics

In this work, CaCu3Ti4O12 modified by Al2O3 (w = 0, 0.05, 0.1, 1%) powders were prepared via a sol–gel process, and then the ceramics were prepared by conventional process using the obtained powders. The dependence of structure and properties of CaCu3Ti4O12 ceramics on the addition fractions of Al2O3 were studied. The results showed that the grain size and density of the samples greatly increase after modifying Al2O3. Moreover, all the samples exhibit giant dielectric properties (~ 104) and relatively low dielectric loss over a wide temperature and frequency range (20–200 °C, 102–106 Hz). The giant dielectric properties of these samples could be explained by the internal barrier layer capacitance (IBLC) model, which consists of semiconducting grains and insulating grain boundaries. Specifically, the optimal Al2O3 modified CaCu3Ti4O12 (w = 0.05%) ceramic shows colossal permittivity (~ 4.29 × 104) and low dielectric loss (~ 0.06) at room temperature and 1 kHz. The results indicated that the microstructures and dielectric properties of CaCu3Ti4O12 were significantly improved after modifying Al2O3.