Effect of sintering on the dielectric properties of 0.5BaTiO₃–0.5Bi_2/3Cu₃Ti₄O₁₂ nanocomposite synthesized by solid state route

A nanocomposite ceramic with the chemical composition 0.5BaTiO₃–0.5Bi_2/3Cu₃Ti₄O₁₂ (BT-BCT 5) was synthesized by a solid-state reaction method at 870 °C for different sintering durations (4, 8, 12 and 16 h). X-ray diffraction analysis confirms the presence of BaTiO₃ and Bi_2/3Cu₃Ti₄O₁₂ phases in the composite ceramic. Transmission electron microscope analysis of the nanocomposite demonstrates the formation of nano-particles (90 ± 10 nm) in the composite. Further, scanning electron microscope (SEM) images show that the morphology consists of large and small grains (1.0–2.5 μm) with a bimodal distribution. The surface morphology of composite was studied by atomic force microscope using tapping mode of measurement also substantiate the results obtained by SEM analysis. The sample sintered for 12 h exhibits very high dielectric constant (ε_r ≈ 43459) at 100 Hz and room temperature. The presence of semiconducting grains with insulating grain boundaries significantly attributes to such a high dielectric constant value, supporting the internal barrier layer capacitance mechanism operative in BT-BCT 5 nanocomposite.