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 $A$2₁am 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 ${\text{Ca}}^{2+}$ compared to ${\text{Pb}}^{2+}$. 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 (${\text{Ca}}^{2+}$ and ${\text{Pb}}^{2+})$ strongly affected the structural, optical and electrical properties of the Aurivillius phase. The occupation of smaller ${\text{Ca}}^{2+}$ cations induced a higher structural distortion, which resulted in higher bandgap ($E_g)$ energy and ferroelectric transition temperature ($T_c)$ 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 $A$2₁am 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 ${\text{Ca}}^{2+}$ compared to ${\text{Pb}}^{2+}$. 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 (${\text{Ca}}^{2+}$ and ${\text{Pb}}^{2+})$ strongly affected the structural, optical and electrical properties of the Aurivillius phase. The occupation of smaller ${\text{Ca}}^{2+}$ cations induced a higher structural distortion, which resulted in higher bandgap ($E_g)$ energy and ferroelectric transition temperature ($T_c)$ of CBT, compared to those of PBT.