Origins of Giant Dielectric Properties with Low Loss Tangent in Rutile (Mg(1/3)Ta(2/3))(0.01)Ti(0.99)O(2) Ceramic

The Mg(2+)/Ta(5+) codoped rutile TiO(2) ceramic with a nominal composition (Mg(1/3)Ta(2/3))(0.01)Ti(0.99)O(2) was synthesized using a conventional solid-state reaction method and sintered at 1400 °C for 2 h. The pure phase of the rutile TiO(2) structure with a highly dense microstructure was obtained. A high dielectric permittivity (2.9 × 10(4) at 10(3) Hz) with a low loss tangent (<0.025) was achieved in the as-sintered ceramic. After removing the outer surface, the dielectric permittivity of the polished ceramic increased from 2.9 × 10(4) to 6.0 × 10(4), while the loss tangent also increased (~0.11). The dielectric permittivity and loss tangent could be recovered to the initial value of the as-sintered ceramic by annealing the polished ceramic in air. Notably, in the temperature range of −60–200 °C, the dielectric permittivity (10(3) Hz) of the annealed ceramic was slightly dependent (<±4.4%), while the loss tangent was very low (0.015–0.036). The giant dielectric properties were likely contributed by the insulating grain boundaries and insulative surface layer effects.