Linear dielectric ceramics for near-zero loss high-capacitance energy storage

High energy-density (W_rec) dielectric capacitors have gained a focal point in the field of power electronic systems. In this study, high energy storage density materials with near-zero loss were obtained by constructing different types of defect dipoles in linear dielectric ceramics. Mg²⁺and Nb⁵⁺ are strategically chosen as acceptor/donor ions, effectively replacing Ti⁴⁺ within Ca_0.5Sr_0.5TiO₃-based ceramics. The results indicate that under an applied electric field, specific defects such as $\left[{Mg}_{Ti}^{″}-V_O^{··}\right]$ and ${[Nb}_{Ti}^{·}-{Ti}^{3+}]$, can effectively regulate $V_O^{··}$ and electron movement, significantly reducing losses. Furthermore, high-density insulating grain boundaries, reduced $V_O^{··}$ concentrations and diminished carrier mobility contribute to enhanced resistivity, resulting in high W_rec ∼7.62 J/cm³ and η ∼92 % at 640 kV/cm, making it one of the most promising linear dielectrics to date. Notably, W_rec and η remain remarkably stable across a broad range of frequencies (1–500 Hz), temperatures (25–175 °C) and numerous cycles (up to 10⁶). Additionally, finite element software was used to simulate the distribution of dielectric constant, electric potential, and local electric field, further verifying the correlation between microstructure and breakdown resistance. This innovative work provides a sustainable strategy to optimize the energy storage capacity of lead-free ceramics over a wide temperature range through strategic manipulation of defects.