Structural and ferroelectric evolution in SrxBa1-xBi2Ta2O9 ceramics: From relaxor to normal ferroelectricity via A-site cation engineering

A series of Aurivillius-type Sr x Ba 1-x Bi 2 Ta 2 O 9 (SBBT, x = 0–1) ceramics were synthesized using a conventional solid-state reaction route and systematically investigated concerning their crystal structure and ferroelectric properties. High-resolution synchrotron XRD refinements indicate that BaBi 2 Ta 2 O 9 crystallizes in the polar A 2 1 am space group rather than I 4/ mmm , confirming the presence of local non-centrosymmetric distortions. A thermal-driven phase transition from orthorhombic to tetragonal is proposed for BBT. The disorder of Ba/Bi cations occurs in BaBi 2 Ta 2 O 9 . Increasing Sr-doping level tends to decrease the orthorhombic structural distortion of Sr x Ba 1-x Bi 2 Ta 2 O 9 . Raman spectroscopy reveals a redshift of the 840 cm −1 band with increasing Sr content x, consistent with the elongated minimum Ta-O distance within TaO 6 octahedra. The x = 0–0.4 compositions exhibit strong dielectric frequency dispersion, while the x = 0.8–1 samples display frequency-independent sharp dielectric peaks. Low-x compositions exhibit pinched P - E loops characteristic of relaxors, whereas high-x samples display squared P - E loops indicative of normal ferroelectrics. Vogel-Fulcher analysis and a phenomenological model reveal that Sr doping suppresses the dynamics of polar nano-region (PNRs) and increases their size across the x = 0–0.4 sample. These phenomena confirm a transition from relaxor to normal ferroelectricity in the SBBT system introduced by increasing Sr-doping level. This work provides new insights into the structure-property correlations in Aurivillius-phase relaxor ferroelectrics, offering guidance for the high-performance energy-storage materials design.