Enhanced Energy Storage and Charge Transport in Nanocrystalline 0.39BaTiO₃–0.31SrTiO₃–0.30KNbO₃ Perovskite Synthesized via Mechanical Milling

Mechanical milling was used to manufacture the ternary nanostructured 0.39BaTiO₃-0.31SrTiO₃-0.30KNbO₃ (BKS) system for periods ranging from 0.5 to 20 hours. Structural investigation corroborated the production of nanocrystalline phases, with HRTEM indicating an average particle size of ~ 44.4nm for the 20-hour milled sample. Dielectric experiments revealed large frequency-dependent permittivity peaks, reflecting the normal relaxor ferroelectric behavior. Thermoelectric investigations verified the n-type semiconducting properties, where electrical conduction is controlled by variable range hopping at intermediate temperatures and adiabatic small polaron hopping at elevated temperatures. At 328 K, the BKS 20h sample had a recoverable energy density of 8.54 mJ cm⁻³ and an efficiency of 60.4%, indicating potential for energy storage capability. An optical study indicated a 2.51 eV direct band gap. Electrochemical analysis revealed a dominating pseudocapacitive behavior accompanied by high specific capacitance of 450 F g⁻¹ at 1 A g⁻¹, low internal resistance, and expeditious charge transfer kinetics. Achieving a maximum energy density of 22.5 Wh kg⁻¹ and a power density of 4800 W kg⁻¹ indicates a beneficial energy-power balance. The unique properties result from the dynamic interaction of the perovskite components, which improves both conductivity and ion mobility. As a result, the BKS 20h nanocomposite stands out as an achievable candidate for next-generation energy storage, dielectric, and optoelectronic technologies.