Dielectric properties of nano-crystalline BaTiO3 synthesized by micro-emulsion method

Ferroelectricity of the thin films consisting of nano-crystalline BaTiO3 by micro-emulsion (ME) method was investigated. Ultra-fine BaTiO3 particle of 8 nm in diameter was obtained. A clear solution of the well-dispersed powder was spin-coated on Si/SiO2/Al2O3/Pt substrate. The crystallinity and particle size were changed with post-annealing from 600 to 1000 °C. Dielectric properties of the films were measured as a function of biasing field, frequency and temperature. It was revealed from the evaluation of dielectric properties and microstructure that annealing at higher than 700 °C provided BaTiO3 thin film with ferroelectricity. Typical ferroelectric D–E hysteresis was observed with thin films of 360 nm thick fired at 700 °C. The ceramic consists of the fine-grains of 18 nm in diameter. Dielectric constant and dissipation factor were 770 and 2.4%, respectively. The grain growth was taken place with elevating the heating temperature. But the grain growth was not as serious as expected. The sample fired at 1000 °C had still fine grain size of 67 nm. The insulation resistance was higher than 109 Ω cm, which is an acceptable vale for capacitor applications.