<p>A comprehensive investigation was carried out to elucidate the influence of A-site cationic off-stoichiometry on the microstructural, structural, dielectric, and electromechanical properties of the lead-free morphotropic phase boundary (MPB) composition 0.93(Na₀.₅Bi₀.₅TiO₃)-0.07BaTiO₃ (NBT-7BT). A series of compositions with controlled sodium and bismuth deviations from stoichiometry were synthesized via the solid-state ceramic synthesis route. The study reveals that A-site off-stoichiometry has a pronounced effect on grain growth and morphology, with Na-rich compositions exhibiting significant grain coarsening. Notably, a 2% Na-excess sample demonstrated a ~ 50% enhancement in the longitudinal piezoelectric coefficient (<i>d₃₃</i>), indicating improved electromechanical performance. Structural analyses of poled samples revealed a higher persistence of the cubic phase in Na-rich compositions, suggesting increased polar-structural heterogeneity. Dielectric spectroscopy showed enhanced dispersion behaviour with increasing off-stoichiometry. These findings highlight the critical role of A-site chemical tuning in modulating phase structure and functional response, providing a viable strategy for the design of high-performance, environmentally benign piezoceramics.</p>