SYNTHESIS AND DIELECTRIC PROPERTIES OF SrBi_2Nb_2O_9 LAYERED PEROVSKITE BY SOL-GEL PROCESSING

摘要

Ferroelectric layered perovskite strontium bismuth niobium oxide SrBi_2Nb_2O_9 (SBN) ceramics and films were made by sol-gel processing. A multiple step hydrolysis-condensation process was applied to the synthesis of the SBN sol by using inorganic salts as precursors with citric acid as a complexing agent. Single phase polycrystalline SBN was obtained after heat-treatment at 650°C. It was found that the dielectric constants of SBN ceramics were dependent on heat-treatment. SEM, XPS, TGA/DTA and XRD analyses indicated that bismuth-deficiency may contribute to the relatively low dielectric constants. While a prolonged firing time at high temperatures may lead to a lattice expansion resulting in a significant decrease of the dielectric constant. C-oriented SBN films were obtained by dip-coating onto SrTiO_3 substrates and the films are dense and crack-free with a thickness of 900 nm.