Engineering crystal structure transformation from layered perovskite-like to pyrochlore for electrostatic energy storage

The pyrochlore phase in ferroelectric materials has long been unaccepted as a negative factor. Therefore, every effort was made to eliminate it. Here, based on electrostatic energy storage capacitors, we provide a counter view to evaluate its effects on ferroelectric properties, i.e., the electrostatic energy storage properties of ferroelectric thin films can be significantly improved by a deliberately designed pyrochlore phase. By adjusting the components and annealing temperature to control crystal structure transformation, an energy storage density of 69 J/cm3 and an efficiency of 70.1% were achieved as a pyrochlore-dominated film, along with good temperature and fatigue stability. It is attribute to its relatively low loss and linear ferroelectric polarization behavior, which enhances the breakdown field while reducing the remnant polarization. These results will provide a versatile strategy for the development of ferroelectric thin film energy storage capacitors with high energy storage density, high efficiency, and good fatigue resistance based on crystal structure transformation.