Colossal dielectric properties in (Ta0.5Al0.5)xTi1−xO2 ceramics

Abstract

In this study, (Ta0.5Al0.5)xTi1−xO2 (x = 0–0.125) and Ta-doped ceramics were fabricated by conventional solid-state method. The phases and microstructures indicate that all ceramics show pure tetragonal rutile TiO2 with different grain size. Notably, by co-doping TiO2 with 0.08 (Ta+Al) ions, a colossal permittivity (εr, ∼6.24 × 104) and low dielectric loss (tan δ, ∼0.05) at room temperature were achieved. While the ceramic doped with same amount of Ta displays the giant εr but higher tan δ value, and the pure TiO2 exhibits a low permittivity value. The co-doped ceramics exhibit more excellent dielectric properties than that of pure TiO2 and Ta-doped TiO2 ceramics when they are subjected to temperature (20–200 °C) and frequency (102–106 Hz) variations. Moreover, the detailed dielectric and impedance spectra analyses for all samples indicate that the colossal permittivity could be explained by the internal barrier layer capacitance (IBLC) model. According to the model, the microstructures of ceramics are consisting of semiconducting grains and insulating grain boundaries, leading to formation of numerous micro-capacitors.