Investigation of Ba_2−xSr_xTiO₄: structural aspects and dielectric properties

Abstract

Investigation of solid solution of barium-strontium orthotitanates of the type, Ba_2−x Sr _x TiO₄ (0 ≤x≤ 2), show that pure phases exist only for the end members, Ba₂TiO₄ and Sr₂TiO₄, crystallizing in the β-K₂SO₄ and K₂NiF₄ structures, respectively. The intermediate compositions (till≥ 1) lead to a biphasic mixture of two Ba₂TiO₄-type phases (probably through a spinodal decomposition) with decreasing lattice parameters, indicating Sr-substitution in both the phases. For x > 1, Sr₂TiO₄ along with a secondary phase is obtained. The dielectric constant and dielectric loss were found to decrease with Sr substitution till the nominal composition of x = 1. However, pure Sr₂TiO₄ shows higher dielectric constant compared to the solid solution composition. Sr₂TiO₄ shows very high temperature stability of the dielectric constant.