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Relaxor ferroelectrics (RFEs) are being actively investigated for energy‐storage applications due to their large electric‐field‐induced polarization with slim hysteresis and fast energy charging–discharging capability. Here, a novel nanograin engineering approach based upon high kinetic energy deposition is reported, for mechanically inducing the RFE behavior in a normal ferroelectric Pb(Zr_0.52Ti_0.48)O₃(PZT), which results in simultaneous enhancement in the dielectric breakdown strength (E_DBS) and polarization. Mechanically transformed relaxor thick films with 4 µm thickness exhibit an exceptionalE_DBSof 540 MV m⁻¹and reduced hysteresis with large unsaturated polarization (103.6 µC cm⁻²), resulting in a record high energy‐storage density of 124.1 J cm⁻³and a power density of 64.5 MW cm⁻³. This fundamental advancement is correlated with the generalized nanostructure design that comprises nanocrystalline phases embedded within the amorphous matrix. Microstructure‐tailored ferroelectric behavior overcomes the limitations imposed by traditional compositional design methods and provides a feasible pathway for realization of high‐performance energy‐storage materials.

Internet of Things (IoT) is driving the development of new generation of sensors, communication components, and power sources. Ideally, IoT sensors and communication components are expected to be powered by sustainable energy source freely available in the environment. Here, a breakthrough in this direction is provided by demonstrating high output power energy harvesting from very low amplitude stray magnetic fields, which exist everywhere, through magnetoelectric (ME) coupled magneto‐mechano‐electric (MME) energy conversion. ME coupled MME harvester comprised of multiple layers of amorphous magnetostrictive material, piezoelectric macrofiber composite, and magnetic tip mass, interacts with an external magnetic field to generate electrical energy. Comprehensive experimental investigation and a theoretical model reveal that both the magnetic torque generated through magnetic loading and amplification of magneto‐mechanical vibration by ME coupling contributes toward the generation of high electrical power from the stray magnetic field around power cables of common home appliances. The generated electrical power from the harvester is sufficient for operating microsensors (gyro, temperature, and humidity sensing) and wireless data transmission systems. These results will facilitate the deployment of IoT devices in emerging intelligent infrastructures.