Ultra–low loss tangent and giant dielectric permittivity with excellent temperature stability of TiO2 co-doped with isovalent-Zr4+/pentavalent-Ta5+ ions

The excellent giant dielectric properties (ExGDPs) are represented in the isovalent–Zr4+/pentavalent–Ta5+ ions co–doped TiO2 with different co–doping percentages (x%ZrTTO). The dopants were dispersed homogeneously in a highly compact–grained ZrTTO microstructure. The mean grain size and cell parameters with bond lengths slightly enlarged as x% increased. The (1%–5%) ZrTTO oxides exhibited ultra–low tanδ values of 0.004–0.016 with the giant dielectric permittivity (ε′∼2.7–3.7 × 104); while the ε′ of the 5%ZrTTO was slightly dependent on the temperature ranging from −60 to 200 °C, following the temperature dependence requirement for application in the X7/8/9R capacitors. Impedance spectroscopy showed a very large resistance of the grain boundaries. The dielectric properties of the 1%ZrTTO were strongly dependent on the applied DC electric field, indicating the dominant internal barrier layer capacitor (IBLC) effect. However, the dielectric properties of the 5%ZrTTO were nearly independent on the applied DC electric field up to 30 V/mm, which was primarily resulted from electron localization in defect dipoles. Therefore, the ExGDPs of the x%ZrTTO were attributed to the combined effects of the IBLC and localized–electron defect–dipoles related to oxygen vacancies (Ti4+⋅e−−VO••−e−⋅Ti4+ and 3Ti4+⋅e−−VO••−TaTi•) and Ti4+⋅e−−TaTi•.