Structural and enhanced dielectric properties of Li-doped BT elaborated by the sol-gel method

In this paper, we studied the effect of lithium doping on the structural, microstructural, dielectric, and electrical properties of Ba_1-xLi_xTiO_3-δ (BTLx) ceramics prepared via the sol-gel method, with x = 0, 0.01, 0.03, 0.05, 0.07 and 0.09. The results obtained from Rietveld refinement of X-ray diffraction, infrared spectroscopy, and Raman spectroscopy show that all the samples crystallize in the tetragonal phase. Dielectric measurements show that increasing the lithium doping rate results in lower dielectric losses (from 0.04 for x = 0 to 0.008 for x = 0.09 at room temperature) and lower transition temperature Tm for compositions with x ≤ 0.07. The phase transition diffusivity parameter γ varies between 1 and 1.39, showing that our samples exhibit a diffuse phase transition but far from relaxor behavior. Complex impedance spectroscopy indicates that the grain boundary resistance of the materials is predominant in the electrical behavior of the materials. The activation energy Ea was calculated at 10 kHz by linear fitting of the temperature dependence of conductivity using the Arrhenius formula. The obtained values indicate that conduction for compositions with 0 ≤ x ≤ 0.05 occurs through free electrons originating from the ionization of oxygen vacancies, while for the compositions with x = 0.07 and 0.09, the predominant conduction mechanism is ionic conduction.