Effects of Sn4+ and Ta5+ dopant concentration on dielectric and electrical properties of TiO2: Internal barrier layer capacitor effect

Abstract

The (Sn1/2Ta1/2)xTi1-xO2.0125 (SnT–TO) ceramics with x = 1.0–5.0 % were prepared by a standard mixed–oxide method. The sintered ceramics showed highly dense microstructures with a single phase of rutile–TiO2 structure. The lattice parameters of the SnT–TO enlarged with increasing x. All the SnT–TO ceramics exhibited a high dielectric permittivity (ε′ > 104) due to the substitution of Ta5+. The ε′ value at 1 kHz increased with increasing the mean grain size. Furthermore, an ultra–low loss tangent (tanẟ<0.05) and low temperature coefficient (<±15 %) were achieved over a wide temperature range, which were attributed to the large grain boundary resistance owing to the substitution of isovalent Sn4+ ions. Hence, the SnT–TO ceramics were suitable for applications in ceramic capacitors. The semiconducting grains and insulating grain boundaries were confirmed using an impedance spectroscopy. The grain resistance increased with increasing Sn4+ ions. In addition, the DC bias dependence of the dielectric properties increased with increasing co–doping concentration. According to the microstructure analysis, dielectric response, and electrical properties, the origin of the high–performance colossal dielectric properties of SnT–TO was well described by the interfacial polarization based on the internal barrier layer capacitor effect.