Yellow to orange-reddish glass phosphors: Sm³⁺, Tb³⁺ and Sm³⁺/Tb³⁺ in zinc tellurite-germanate glasses

An optical spectroscopy analysis of TeO-GeO₂-ZnO glass co-activating Sm³⁺/Tb³⁺ ions was carried out through Raman, photoluminescence spectra and decay time profiles as a function of Sm³⁺ concentration. According to the estimated CIE1931 chromaticity coordinates, the color of the emission can be adjusted from the yellow light region (0.4883, 0.4774), towards the reddish light region (0.5194,0.4144) by increasing the Sm³⁺ content from 1, 3, 5% mol, co-doped with 1% mol Tb³⁺ under co-excitation of Sm³⁺ and Tb³⁺ at 378 nm. The color temperatures are in the range of 1379–2804 K. Such photoluminescence is generated by the ⁴G _5/2 → ⁴H _5/2, ⁴H _7/2, ⁴H_9/2 emissions of Sm³⁺ in addition to the ⁵D₄→⁷F_6,5,4,3 emissions of Tb³⁺; the single doped Sm³⁺ glass displayed an intense orange light. Meanwhile, co-doped Sm³⁺/Tb³⁺ glasses excited at 378 nm showed a significant reduction in Tb³⁺ emission, with a simultaneous increment in the reddish-orange emission of Sm³⁺, due to a non-radiative resonant energy transfer from Tb³⁺ to Sm³⁺. Decay time profile analysis of the Tb³⁺ emission as function of Sm³⁺ ion content suggests that an electric dipole–dipole interaction into Tb³⁺–Sm³⁺ clusters might dominate in the energy transfer process, with an efficiency and probability of 0.22, 0.27, 0.38 and 122.8, 327.6, 522.7 s⁻¹, respectively.