Two sol-gel methods (via chlorides and nitrates) of synthesis: theory and experimental investigation of ceramic powders of Tb3+-doped Eu2O3

For this research, two sol-gel methods (via chlorides and nitrates) using the Pechini variant assisted by epoxide were theoretically and practically established to obtain ceramic powders of europium oxide (Eu₂O₃) xerogels undoped and doped with different molar concentrations of the trivalent terbium ion (Tb³⁺: 0.01, 0.025, 0.05, 0.075 and 0.1 mol %). This study aimed to determine if there would be differences or changes in the luminescent properties of the Eu³⁺, as well as in its morphological/structural properties, due to interaction with the Tb³⁺ ion. Through infrared (IR) spectroscopy, the formation of M-O-M bonds, typical of materials synthesized with rare-earth oxides, was demonstrated. The characteristic bands of the vibrational modes of Eu₂O₃ were observed by Raman studies using an argon laser at 532 nm. According to the results of the luminescence analysis, the materials exhibit the transitions ⁵D₀-⁵F₁, ⁵D₀-⁵F₂, ⁵D₀-⁵F₃, and ⁵D₀-⁵F₄, which are characteristic of the red/orange photoluminescence of the trivalent europium ion (Eu³⁺). XRD was used to determine the composition of the ceramic powders and to define the crystalline structures as cubic type. Finally, the micrographs were analyzed with SEM to compare the morphologies and obtain the average particle size.

Graphical abstract

Synthesis scheme of Eu₂O₃:Tb³⁺: (a) v ch and (b) v nt.