Barium titanate is a classical ABO₃ perovskite known for its high dielectric constant, ferroelectricity, and strong piezoelectric response, all of which are preserved and tunable at the nanoscale through particle size and phase control. BaTiO₃ nanoparticles exhibit excellent thermal and chemical stability together with size-dependent dielectric and band-gap properties. These features make them widely used in multilayer ceramic capacitors, piezoelectric sensors and actuators, electro-optic devices, and energy harvesting systems, as well as in emerging applications such as photocatalysis and bio-compatible functional materials.