Preparation of BaTi4O9 and Ba2Ti9O20 ceramics by the wet chemical gel-carbonate method and their dielectric properties

Preparation of BaTi4O9 and Ba2Ti9O20 ceramics by the wet chemical gel-carbonate method, and their microstructural and dielectric properties are presented. Monophasic Ba2Ti9O20 of triclinic symmetry having high dielectric constant (ɛr ∼ 52 at 1 MHz), low temperature coefficient of dielectric constant (τɛ ∼ 6 ppm/°C) and moderate quality factor (Q > 2000) could be realized on sintering at 1300 °C. These ceramics are prepared by using Ba and Ti compounds in 1:4.5 molar ratio in the reaction. But phase singular BaTi4O9 ceramics could not be synthesized by this method. The sintered ceramics obtained when Ba and Ti compounds are in 1:4 molar ratio, are associated with Ba4Ti13O30 phase that impart higher τɛ values. However by using Ba and Ti compounds in 1:4.1 molar ratio, sintered ceramics containing BaTi4O9 as well as Ba2Ti9O20 could be prepared. Such ceramics possess intermediate dielectric properties with ɛr, τɛ and Q being 23–50, ≥4 ppm/°C and ≥2000, respectively. The dielectric properties of the ceramics depend considerably on sintering temperature and their microstructure.