Influence of surface coating on the microstructures and dielectric properties of BaTiO 3 ceramic via a cold sintering process.

We present herein a modified cold sintering process (CSP) for BaTiO 3 ceramics using a surface coating at the particle surface which could enhance the relative density of BaTiO 3 up to ∼93.5% at 220 °C and 500 MPa. The surface coating greatly enhances the ceramic density, mainly because it facilitates the dissolution-precipitation process during CSP. Ba vacancies form at the surface of the coated powders, so Ba(OH) 2 solution is used to compensate Ba ions in the as-cold-sintered ceramics, which increases the dielectric permittivity. Post-annealing at 700 and 900 °C increases the relative density to 97%, and the resulting relative dielectric permittivities are 810 and 1550, respectively, at room temperature and 1 kHz. This technique may also be extended to materials with very small, incongruent solubility in water or volatile solutions that use the cold sintering process.