Dielectric relaxation and conduction behaviors of Aurivillius Na_0.5Bi_4.5Ti₄O₁₅ ceramics with Na doping

Aurivillius Na_0.5Bi_4.5Ti₄O₁₅ and Bi₄Ti₃O₁₂ compounds were synthesized via solid-state reaction technique. X-ray powder diffraction study confirmed monophasic four-layered Na_0.5Bi_4.5Ti₄O₁₅ and three-layered Bi₄Ti₃O₁₂ ceramics. Dielectric relaxation and conduction behaviors of Na-contained Na_0.5Bi_4.5Ti₄O₁₅ ceramics were thoroughly investigated in a large scale of temperature of 30–650 °C and frequency of 40 Hz–1 MHz. In addition, comparative studies of both the compounds were discussed. Impedance and modulus analyses revealed a single relaxation behavior in Na_0.5Bi_4.5Ti₄O₁₅ compound which was originated from the grain’s interior with grain resistance of 2.189 × 10⁵ Ω and capacitance of 4.268 × 10⁻¹⁰ F at 570 °C. While in Bi₄Ti₃O₁₂ ceramic the relaxation was due to the contributions of grain and grain boundaries. Alternating current (AC) conductivity analysis revealed the presence of two different conduction regions in both the compounds. Activation energies for the two different conduction mechanisms, i.e., in low-temperature region and in high-temperature region were calculated to be ~ 0.23 and ~ 1.27 eV at 1 kHz for Na_0.5Bi_4.5Ti₄O₁₅ compound and ~ 0.43 eV and ~ 0.97 eV at 1 kHz for Bi₄Ti₃O₁₂ compound, respectively. The present study of dielectric relaxation and conduction behaviors would be helpful for further investigations of Na_0.5Bi_4.5Ti₄O₁₅-related Aurivillius compounds.