Colossal and tunable dielectric tunability in domain-engineered barium strontium titanate

Realization of tunable materials that are multifunctional and maintain high performance in dynamically changing environments is a fundamental goal of science and engineering. Tunable dielectrics form the basis of a wide variety of communication and sensing devices and require breakthrough performance improvement to enable next-generation technologies. Using phenomenological modeling, film growth, and characterization, we show that devices consisting of domain-wall-rich Ba_0.8Sr_0.2TiO₃ films close to a polar-domain-variant phase boundary exhibit colossal dielectric tunability of 100:1 (99%) at a voltage (electric field) of ~15 V (750 kV/cm), resulting in a tunability-quality factor product figure of merit that rises to nearly 10⁵, two orders of magnitude higher than the best previous reported values. Remarkably, varying the amplitude of alternating-current bias enables modulation of this tunability by 50%, owing to domain-wall motion. These results suggest that domain engineering is a powerful approach for achieving excellent modulation of functional properties in ferroelectric films.