Large-size-mismatch co-dopants for colossal permittivity rutile TiO2 ceramics with temperature stability

Abstract Colossal permittivity (CP) in donor-accepter co-doped rutile TiO 2 has attracted significant interest. Here, the CP behavior of (Ta + La) co-doped rutile TiO 2 ceramics were studied, where the ionic radii of Ta 5+ and La 3+ are much larger than that of Ti 4+ . The ceramics with an extremely low doping exhibit colossal dielectric permittivity (∼2.6 × 10 4 ) with an acceptable low dielectric loss ( 6  Hz. The CP properties obtained in (Ta + La) co-doped TiO 2 ceramics show excellent temperature stability over a wide temperature range of 20–400 °C. The X-ray diffraction analysis and the density functional theory calculation illustrates that the La 2 3+ V o • • Ti 2 3+ and Ta 2 5+ Ti 3+ Ti 4+ defect complexes with the lowest energy are responsible for the enhanced dielectric properties. Moreover, the defect complex formed by large-size trivalent substitutions and oxygen vacancy is very stable, and assists in improving temperature stability of the dielectric properties of co-doped rutile TiO 2 ceramics.