In this study, the double-layered Aurivillius phases CaBi₂Ta₂O₉ (CBT) and PbBi₂Ta₂O₉ (PBT) were prepared through a hydrothermal route with NaOH as a mineralizer. XRD analysis confirmed that the CBT and PBT compounds were successfully formed and adopted an orthorhombic crystal structure with an A2₁am symmetry. Le Bail refinements of XRD data indicated that the unit cell volume of CBT was smaller than PBT and is associated with the smaller ionic radius of Ca2+ compared to Pb2+. The surface morphology of both samples, as determined using SEM, demonstrated plate-like grains with anisotropic grain growth. It was found that the different ionic radii of A-site cations (Ca2+ and Pb2+) strongly affected the structural, optical and electrical properties of the Aurivillius phase. The occupation of smaller Ca2+ cations induced a higher structural distortion, which resulted in higher bandgap (Eg) energy and ferroelectric transition temperature (Tc) of CBT, compared to those of PBT.In this study, the double-layered Aurivillius phases CaBi₂Ta₂O₉ (CBT) and PbBi₂Ta₂O₉ (PBT) were prepared through a hydrothermal route with NaOH as a mineralizer. XRD analysis confirmed that the CBT and PBT compounds were successfully formed and adopted an orthorhombic crystal structure with an A2₁am symmetry. Le Bail refinements of XRD data indicated that the unit cell volume of CBT was smaller than PBT and is associated with the smaller ionic radius of Ca2+ compared to Pb2+. The surface morphology of both samples, as determined using SEM, demonstrated plate-like grains with anisotropic grain growth. It was found that the different ionic radii of A-site cations (Ca2+ and Pb2+) strongly affected the structural, optical and electrical properties of the Aurivillius phase. The occupation of smaller Ca2+ cations induced a higher structural distortion, which resulted in higher bandgap (Eg) energy and ferroelectric transition temperature (Tc) of CBT, compared to those of PBT.