High breakdown electric field and ultralow loss in Sb+Ho co-doped TiO2 giant dielectric ceramics induced by strongly coupled defect clusters

Achieving a large dielectric constant and high breakdown electric field simultaneously has been a hot and difficult topic for co-doped TiO₂ ceramics. In this study, (Sb_0.5Ho_0.5)_xTi_1–xO₂ (SHTOx, x = 0, 0.01, 0.02, 0.04 and 0.06) ceramics with strongly coupled defect clusters were prepared to improving the dielectric and breakdown properties. In particular, the SHTO0.01 ceramic exhibits CP (ε′ = 1.61 × 10⁴, 1 kHz), ultralow loss (tanδ = 0.0037, 1 kHz), excellent DC bias (0–400 V/cm) and thermal stability (Δε′/ε′_25 °C ≤ ±15% at 1 kHz, −145 to 215 °C). Besides, high dielectric breakdown properties (E_b ∼2.287 kV/cm and α = 7.24) was also achieved. Meanwhile, the mechanism of achieving excellent overall properties was deeply explored by XPS, UDR law, impedance spectroscopy and relaxation behavior analysis. The high dielectric and breakdown field strength performances mainly originate from the strongly coupled defective dipole clusters and the highly insulating grain boundaries as well as electrode-ceramic interfaces, which synergistically restrict the long-range movement of free electrons. This research indicates that the construction of defect clusters with strong coupling is an effective approach towards obtaining CP ceramics with ultra-low loss and high breakdown field strength performances.