Frequency and temperature independent (Nb_0.5Ga_0.5)_x(Ti_0.9Zr_0.1)_1-xO₂ ceramics with giant dielectric permittivity and low loss

Nb⁵⁺ and Ga³⁺ co-doped Ti_0.9Zr_0.1O₂ ceramics were synthesized using the conventional solid-state reaction method. Single rutile-liked phase of octahedron structure were identified for all compositions in (Nb_0.5Ga_0.5)_x(Ti_0.9Zr_0.1)_1-xO₂ (NGT) with x = 0.01 to 0.10 by X-ray diffraction patterns coupled with Rietveld refinement. Microstructural scanning image, together with energy dispersive x-ray spectroscopy (EDX), revealed good chemical homogeneity in NGT samples. A giant dielectric permittivity of 5 × 10⁴ and a low loss of 0.02 was obtained in NGT with x = 0.01 due to the contribution of electron-pinned and defect-dipole effect. Furthermore, a temperature (-20–120 °C), frequency (0.1–10⁴ Hz) and bias electric field (100–200 V/mm) independent dielectric permittivity and loss was found in this composition, which is critical for potential applications of supercapacitors.