Work

Dielectric Properties of Co-Doped TiO2 with Mg and Nb for Energy Storage Applications

Year: 2025

Type: article

Abstract: Titanium dioxide is attractive for energy storage due to its abundance, stability, non-toxicity, low cost, and favorable electronic/optical properties. Colossal permittivity (CP) in co-doped TiO2 is mainly linked to defect structures rather than intrinsic bulk behavior. This work studies the dielectric properties of TiO2 co-doped with niobium and magnesium, synthesized by solid-state reaction. Grain size effects were examined by varying ball milling parameters of (½Mg½Nb)0.05Ti0.95O2 and then were correlated with structure, morphology, and dielectric response. X-ray diffraction (XRD), infrared spectroscopy (FTIR), scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS), and impedance spectroscopy (IS) (40 Hz–106 Hz, 150–370 K) were employed for structural, morphological, and electrical characterization. XRD confirmed the rutile phase. For co-doped samples, larger grains yielded higher dielectric constants, reaching high permittivity (ε′ = 429, T = 300 K, f = 10 kHz at 500 rpm for 2 h). Lower loss tangent (tan δ = 0.11, T = 300 K, f = 10 kHz at 200 rpm for 2 h) is linked to Mg segregation at grain boundaries. The most conductive sample showed the highest dielectric constant, suggesting an IBLC polarization mechanism driven by grain boundary effects. XPS confirmed Nb and Mg incorporation, with Ti4+ dominant and minor Ti3+ from oxygen vacancies and surface hydroxylation/defects.

Source: Nanomaterials

DOI: 10.3390/nano15211632