Diffuse to normal ferroelectric transition in Gd-substituted BBTO Aurivillius ceramics

A comprehensive investigation of the structural, microstructural, ferroelectric, and dielectric relaxation characteristics was accomplished on Gd-substituted barium bismuth titanate (BaBi₄Ti₄O₁₅) (BBTO) Aurivillius ceramics. The Rietveld refined X-ray diffraction confirmed that the low-concentration (≤ 0.10) of Gd ions as a more stable orthorhombic with A2₁am phase and to higher concentration (> 0.10) as dual phase orthorhombic “A2₁am + F2mm” space group. The inherent plate-like grain morphology was characterized by a scanning electron microscope. A discernible microstructural phonon modification in Raman spectroscopy analysis exposed changes with temperature variations confirms of dual-phase pattern at increased dopant concentrations. T-dependent dielectric study reveals a shifting Curies Weiss ( \({T}_{m}\) $T_m$ ) transition towards lower temperature was noticed with an increase of Gd dopant. The relaxor ferroelectric phase transitions were detected using the modified Curie–Weiss law such as Vogel–Fulcher (VF), Cluster Glass (CG), and Stretched string (SS) models. The VF fitting was more stabilized for lower concentrations (Gd; x ≤ 0.10). Furthermore, the CG model was appropriate for the higher concentration of dopant (Gd; x > 0.10) indicating the stabilization of the relaxor ferroelectric nature. The temperature-dependent dielectric studies reveal a normal ferroelectric to relaxor ferroelectric crossover of 0.20 implying a reduction in interaction within the polar regions. The observed relaxor-like dielectric behavior suggests the generation of small-sized polar regions due to an imbalance of charge in compensation of the Bi₂O₂ layer for higher dopant concentrations. The randomly weak interaction between the small polar regions leads to a critically slowed down of polar regions dynamics below. The soft ferroelectric P-E loops with weak loop character of well predominant shape were observed in Gd-substitution BBTO ceramics.