Na–Ni co-substitution induced simultaneous enhancement of dielectric constant and breakdown field in CaCu3Ti4O12 ceramics: A mechanism study

: Due to conflicts in physical mechanisms, simultaneously improving the dielectric constant ( ε ˊ) and breakdown field strength ( E b ) of dielectric materials remains challenging. Fortunately, progress has been made in addressing this issue, though the underlying mechanisms still require further investigation. In this study, Ca 1– x Na x Cu 2.95 Ni 0.05 Ti 4 O 12 ( x =0, 0.003, 0.005, 0.007) ceramics were prepared, and the sample with x =0.005 exhibited significant enhancement in both ε ˊ and E b . Through density functional theory calculations and X-ray photoelectron spectroscopy, Na doping is confirmed to promote Cu + and concentration, while Ni increases Ti 3+ content. Notably, Cu + and Ti 3+ together enhance ε ˊ, and the increased forms depletion layers to improve E b . These findings clarify the synergistic mechanism of Na–Ni co-doping for the simultaneous improvement of ε ˊ and E b in CCTO ceramics. They not only provide research insights for the composition design of high performance ceramic capacitors but also hold great promise for the development of high energy density dielectric ceramics.