Microstructural and dielectric properties of ceramics based on K2Sr4Nb10O30 and BaTiO3

The search for dielectric materials with a high dielectric constant and ε curves with a flat profile is still ongoing. K₂Sr₄Nb₁₀O₃₀-based dielectric ceramics, having the tetragonal tungsten bronze structure (TTB), which display a high permittivity and flat ε curves meeting the X7R specification. BaTiO₃-based ferroelectric ceramics are classic dielectric materials for ceramic capacitors. Results were obtained by mixing compounds with closely related structures, such as the tetragonal tungsten bronze (TTB) niobate K₂Sr₄Nb₁₀O₃₀ (KSN) and the perovskite BaTiO₃ (BT). Phase compositions were analyzed by using XRD and the microstructure was investigated by SEM. The present study explores the dielectric curves ε of the composition (K₂Sr₄Nb₁₀O₃₀)_x·(BaTiO₃)_1-x with x = 0.1-0.9 where x means the weight ratio of KSN. The dielectric constant at room temperature is lowest at x = 0.4. When x is between 0.4 and 0.7, ε curves of the ceramic composites present a linear decrease with the temperature. Two different phases, TTB and perovskite type, are present after sintering.