In this study, a KNN–barium stannate ceramic composite was designed at the near R–O–T phase boundary to achieve simultaneous enhancement of piezoelectric performance and thermal stability through stabilization of multiple ferroelectric phases. Unlike conventional KNN-based systems that often exhibit either high \({d}_{33}\) or high Curie temperature, the present ternary composition demonstrates a balanced combination of both properties, achieving a high piezoelectric coefficient of 375 pC/N together with a Curie temperature of 351 °C. The sintering temperature was systematically optimized, with the best performance obtained at 1100 °C under an optimized poling field of 4 kV/mm. FESEM analysis revealed microstructural evolution with sintering temperature, while Raman spectroscopy confirmed structural modifications associated with the broadened R–O–T phase boundary. BET and UV–Vis studies were also performed to investigate the surface area and optical band gap of the optimized composition. Beyond conventional piezoelectric characterization, the developed ceramic demonstrated efficient energy harvesting under low-intensity acoustic excitation and exhibited stable electromechanical performance under extreme shockwave conditions up to Mach 2.2 and 2 MPa. The combined demonstration of high-temperature piezoelectricity, acoustic energy harvesting, and shockwave-responsive sensing behavior highlights the novelty and multifunctional potential of the developed system for advanced sensing applications.
