Effect of Fe/Ta doping on structural, dielectric, and electrical properties of Bi₄Ti_2.5Fe_0.25Ta_0.25O₁₂ ceramics

Aurivillius single-phase Bi₄Ti_2.5Fe_0.25Ta_0.25O₁₂ ceramics was prepared via high-temperature solid-state reaction method. The detailed structural analysis of the doped Bi₄Ti₃O₁₂ compound was carried out by Rietveld refinement of the full XRD Pattern. Dielectric and electrical properties were studied in a wide range of temperature and frequency by dielectric/impedance spectroscopies. The comprehensive analysis of frequency spectrum reveals the occurrence of two relaxation behaviors in the ceramics at low frequency and high frequency, respectively. A phase transition was observed at ~650°C in Bi₄Ti_2.5Fe_0.25Ta_0.25O₁₂ somewhat lower than the ferroelectric transition temperature of Bi₄Ti₃O₁₂. The possible reason for the decrease of ferroelectric transition temperature was discussed based on the structural analysis. The present results could be useful for designing and/or modifying properties of Bi₄Ti₃O₁₂-related ceramics.