In this paper, a series of Rb⁺-doped Er³⁺/Yb³⁺–Y₂O₃ films were synthesized via a sol-gel method and spin coating. The structure and morphology of the samples were investigated by X-ray diffraction and scanning electron microscopy. The Rb⁺-doped films with nanoparticles, in the size range of 20–40 nm, were obtained. The spectroscopic analysis of the samples was investigated by using the emission spectra and the intensity of luminescence. All the samples exhibited a green emission ascribed to ²H_11/2/⁴S_3/2 to ⁴I_15/2 of Er³⁺ and a red one ascribed to ⁴F_9/2 and its stark level to ⁴I_15/2 of Er³⁺. As the Rb⁺ concentration increased, the intensities of the green light and red light were enhanced 16.97- and 5.81-fold relative to that of the undoped sample. Moreover, by controlling the Rb⁺ concentration, the samples were capable of generating color-tunable luminescence from red to green linearly. The tunable emission was caused by the change of ion distribution ratio in ⁴F_7/2(Er) and ⁴F_9/2(Er) levels. The results suggest that the as-prepared Rb⁺-doped Er³⁺/Yb³⁺–Y₂O₃ films have a great potential for applications of luminescence.

In this study, a series of well-crystallized Yb³⁺/Er³⁺/Tm³⁺-tridoped Y₂O₃-ZnO ceramic nano-phosphors were prepared using sol–gel synthesis, and the phosphor structures were studied using X-ray diffraction, scanning electron microscopy, and thermogravimetric analysis. The phosphors were well crystallized and exhibited a sharp-edged angular crystal structure and mesoporous structure consisting of 270 nm nano-particles. All phosphors generated blue, green, and red emission bands attributed to Tm: ¹G₄→³H₆, Er: ²H_11/2 (⁴S_3/2)→⁴I_15/2, and Er: ⁴F_9/2→⁴I_15/2 radiative transitions, respectively. Increasing in luminescent centers, weakening of lattice symmetry, and releasing of dormant rare earth ions can enhance all emissions. Er³⁺ can obtain energy from Tm³⁺ to enhance green and red emission. These colors can be tuned by optimizing the doping concentrations of the Er³⁺ ion. The color coordinates were adjusted by tuning both the Er³⁺ concentration and excitation laser pump power to shift the color coordinates and correlated color temperature. The findings of this study will broaden the potential practical applications of phosphors.