Abstract
The linear-like relaxor ferroelectric Sr0.7Bi0.2TiO3 with regulable microstructure offers a new platform to reveal the essential mechanism of energy storage properties improvement and develop advanced pulse capacitors. Herein, Li with relatively weak volatility accompanied by Bi was introduced in Sr0.7Bi0.2TiO3 to form a charged defect and increase the maximum polarization (Pmax) while avoiding the deterioration of dielectric breakdown strength (BDS). The occupation of Li and the formation of Li-Bi defect dipole polar were analyzed using first principle calculations. A unique local superlattice induced by the lattice distortion was first observed in related systems. The Pmax was enhanced due to the increased size and number of polar structures. The breakdown behaviour and local electric field distribution were analyzed using numerical simulation. The BDS was improved due to the decreased oxygen vacancies, high thermal conductivity and enhanced electrical insulation. The excellent and stable energy storage performance was achieved in different temperatures, frequencies and cycles. Meanwhile, the optimized sample possesses excellent and stable charge–discharge properties, especially fatigue resistance (105 cycles under 25 °C and 150 °C). After the process optimization, the sample shows a higher energy storage density of 3.44 J/cm3 with a high efficiency of 93.74 % at 345 kV/cm due to the further enhanced BDS. In this work, the performance improvement mechanism was studied in-depth, providing a new strategy for optimizing linear-like lead-free relaxor ferroelectric energy storage properties.
Published Version
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