Colossal and anomalous dielectric behavior in grain-oriented TiO2

Abstract

In this work, anatase structure TiO2 particles with a preferential grain growth direction of [002] were synthesized by a facile and modified sol–gel approach. The pellets pressed from the TiO2 particles possess colossal dielectric constant (> 7 × 103 at 100 Hz and room temperature). The colossal dielectric constant behavior can be associated with the Maxwell–Wagner relaxation due to the textured grain structure. This approach is simple and provides an avenue to obtain the excellent dielectric properties of ceramics with oriented grains. Contrary to traditional relaxation behavior, an anomalous dielectric behavior was observed above room temperature. This abnormal dielectric behavior was caused by the positive temperature coefficient of resistance effect resulting from humidity response.