High-performance giant-dielectric properties of rutile TiO2 co-doped with acceptor-Sc3+ and donor-Nb5+ ions

Giant dielectric properties of materials have widely been reported in recent years. However, a simultaneously low dielectric loss tangent (tanδ) and high dielectric permittivity (ɛ′) with a low temperature coefficient (Δɛ′(T)/ɛ′RT) have been very difficult to achieve. In this work, high performance of giant dielectric properties were achieved in rutile-TiO2 ceramics by co-doping with acceptor-Sc3+ and donor-Nb5+ ions. The important role of the former dopant was to capture free electrons at internal insulating layers, playing as an acceptor. The latter dopant was used to produce free electrons. Ceramics that were 10% (Sc3++Nb5+) co-doped TiO2 (10%ScNTO) exhibited very low tanδ≈0.016-0.035 and high ɛ′≈103-104 values. By optimizing the sintering conditions, excellent temperature stability of ɛ′ at 1 kHz with Δɛ′(T)/ɛ′RT < ±15% was obtained over a wide temperature range, meeting the requirement for use in X8R capacitors. Furthermore, the dielectric properties were slightly dependent on applied DC bias. Impedance spectroscopy analysis revealed that the ScNTO ceramics were electrically heterogeneous, consisting of semiconducting grains and very high insulating layers. The high-performance giant-dielectric properties of ScNTO ceramics were attributed to interfacial polarization at insulating layers with very high resistivity and large activation energy.