Colossal dielectric performance of pure barium titanate ceramics consolidated by spark plasma sintering

Abstract

A facile sol–gel-hydrothermal method was developed to prepare well-dispersed BaTiO₃ (BT) nanocrystals with a size of about 20 nm. By using such nanopowder, dense BT nanoceramics were densified via spark plasma sintering (SPS). Dielectric measurements reveal that pure BT nanoceramics have an extremely high permittivity up to 6 × 10⁴ and a low dielectric loss. On the basis of microstructure characterization and dielectric measurement, it was proposed that the polaron dipoles configured by oxygen vacancies and Ti³⁺ cations within the grains could contribute to the colossal dielectric permittivity of the ceramics. By using the thermally activated polaron hopping model, a large activation energy E_A has been determined (0.135 eV) below the Curie temperature, possibly due to the coupling of polaron dipoles and intrinsic ferroelectric dipoles. This simple method offers the possibility to produce pure BT nanoceramics with a colossal permittivity.