Microstructure, dielectric response and impedance spectroscopy of SrCu3Ti4O12 ceramics prepared by a sol-gel technique

SrCu3Ti4O12 ultrafine powders and ceramics were successfully prepared using sol-gel and ceramic techniques. DTA/TG, XRD, HRTEM, SAED, SEM, and XPS were employed to characterize the samples' thermal decomposition, phase composition, microstructure, and element valence. During calcination, the dry precursors gradually decompose into oxides and recombine into SrCu3Ti4O12 polycrystalline above 620 °C. Simultaneously, the prepared ceramics sintered at 1025 °C for 8 h exhibited a colossal permittivity at room temperature (εr = 8.5 × 104, 1 kHz) and good temperature stability. XPS result confirms that Cu+/Cu2+ and Ti3+/Ti4+ coexist in ceramics, and Impedance analysis indicates a low-resistance region originating from inhomogeneity in the grain interiors. Finally, the relevance between defect formation and dielectric properties in SrCu3Ti4O12 materials is discussed.