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The synthesis and characterization of multicolor light-emitting nanomaterials based on rare earths (RE³⁺) are of great importance due to their possible use in optoelectronic devices, such as LEDs or displays. In the present work, oxyfluoride glass-ceramics containing BaF₂ nanocrystals co-doped with Tb³⁺, Eu³⁺ ions were fabricated from amorphous xerogels at 350 °C. The analysis of the thermal behavior of fabricated xerogels was performed using TG/DSC measurements (thermogravimetry (TG), differential scanning calorimetry (DSC)). The crystallization of BaF₂ phase at the nanoscale was confirmed by X-ray diffraction (XRD) measurements and transmission electron microscopy (TEM), and the changes in silicate sol–gel host were determined by attenuated total reflectance infrared (ATR-IR) spectroscopy. The luminescent characterization of prepared sol–gel materials was carried out by excitation and emission spectra along with decay analysis from the ⁵D₄ level of Tb³⁺. As a result, the visible light according to the electronic transitions of Tb³⁺ (⁵D₄ → ⁷F_J (J = 6–3)) and Eu³⁺ (⁵D₀ → ⁷F_J (J = 0–4)) was recorded. It was also observed that co-doping with Eu³⁺ caused the shortening in decay times of the ⁵D₄ state from 1.11 ms to 0.88 ms (for xerogels) and from 6.56 ms to 4.06 ms (for glass-ceramics). Thus, based on lifetime values, the Tb³⁺/Eu³⁺ energy transfer (ET) efficiencies were estimated to be almost 21% for xerogels and 38% for nano-glass-ceramics. Therefore, such materials could be successfully predisposed for laser technologies, spectral converters, and three-dimensional displays. Full article