Pioneering dielectric materials of Sn-doped NbTiO ceramics with excellent temperature and humidity stability for advanced ceramic capacitors

In this study, the rutile TiO 2 system, widely acclaimed for its superior properties, was enhanced through co-doping with isovalent Sn 4+ ions and 2.5% Nb 5+ donor ions, diverging from traditional acceptor doping practices. This novel doping strategy was implemented by employing a conventional solid-state reaction method, resulting in the synthesis of Sn-doped Nb 0.025 Ti 0.975 O 2 (Sn-NTO) ceramics. These ceramics demonstrated remarkable dielectric characteristics, with a high dielectric constant ( ′) ranging from ∼27 000 to 34 000 and an exceptionally low loss tangent between 0.005 and 0.056 at ∼25 °C and 1 kHz. Notably, the temperature coefficient of ′, , aligned with the stringent specifications for X7/8/9R capacitors. Furthermore, the Sn-NTO ceramics exhibited a stable C p response across various frequencies within a humidity range of 50 to 95% RH, with Δ C p (%) values within ±0.3%, and no hysteresis loop was detected, suggesting the absence of water molecule adsorption and desorption during humidity assessments. This behavior is primarily attributed to the effective suppression of oxygen vacancy formation by the Sn 4+ ions, which also affects the grain growth diffusion process in the Sn-NTO ceramics. The observed heterogeneous electrical responses between semiconducting grains and insulating grain boundaries in these polycrystalline ceramics are attributed to the internal barrier layer capacitor effect. The dielectric properties exhibit excellent stability across a wide range of temperatures. Additionally, the capacitance is almost exclusively dependent on humidity levels.