Dielectric properties of (N, B) and (N, Cl) co-doped rutile TiO2 ceramics

Extensive studies on TiO₂-based colossal permittivity (CP, dielectric constant ε’ >10³) materials have focused on the cation doping of metal elements; however, little attention has been paid to nonmetallic dopants. Compared to metallic elements, nonmetallic atoms with small radii and high activities, such as H, C, B, and N, can be used as anion-doping elements. Their incorporation into the TiO₂ lattice includes interstitial and substitutional doping, which can influence the bandgap of TiO₂ and its electron transport performance differently, thereby exhibiting considerable potential in TiO₂-based applications. In this study, different N-containing compounds (BN and NH₄Cl) were doped into rutile TiO₂, while homogeneous ceramics of single-phase rutile TiO₂ were prepared via solid-state sintering. The effects of co-doping N, Cl, and N, B on the dielectric properties of rutile TiO₂ ceramics were investigated. While N and Cl doping showed no considerable effect on the dielectric properties of rutile TiO₂ ceramics, the co-doping of N and B doping in rutile TiO₂ considerably increased the dielectric constant to >10⁴ with suppressed tan δ in a wide frequency range from 1 kHz to 10 MHz. These ceramics exhibited excellent frequency stability (up to 100 MHz) and temperature stability (153–513 K), which outperforms most reported transition metal co-doped TiO₂ ceramics, thereby highlighting the untapped potential of the non-metallic dopants in enhancing dielectric materials.