In present work, doping modified SrBi1.98La0.02Nb2-xTaxO9; x = 0.0–2.0 in steps of 0.5 (SBLNT) matrix is investigated for typical potential barrier formation yielding delayed dielectric relaxation and repair of weak ferroelectric character due to deterioration post microwave synthesis. Unit cell regularizes to tetragonal character on doping tantalum compared to dominant orthorhombic nature of undoped SrBi1.98La0.02Nb2O9 SBLN sample. Regular decrease in c-axis strain in the presence of fix lanthanum content is due to increased electrostatic repulsion along a-b plane on doping tantalum. Strong correlation between 4f-electrons of tantalum and intense sp3-hybridization between Ta(4f)-O(2p) electrons is discussed as a major cause for holding any unbound charge without participating in conduction. Complex impedance and modulus spectroscopy both confirm growth of highly resistive grain boundaries in sample with 50% tantalum doping. Poled and unpoled ferroelectric hysteresis loops for all samples indicate rise in ferroelectric hardness on increase in tantalum doping besides decreasing pore-size. © 2021 Elsevier B.V.