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 degrees 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 degrees C provided BaTiO3 thin film with ferroelectricity. Typical ferroelectric D-E hysteresis was observed with thin films of 360 nm thick fired at 700 degrees 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 degrees C had still fine grain size of 67 nm. The insulation resistance was higher than 109 Omega cm, which is an acceptable vale for capacitor applications. (c) 2005 Elsevier Ltd. All rights reserved.