Influence of surface coating on the microstructures and dielectric properties of BaTiO3 ceramic via a cold sintering process.

Abstract

We present herein a modified cold sintering process (CSP) for BaTiO3 ceramics using a surface coating at the particle surface which could enhance the relative density of BaTiO3 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.