Tunable color, optical properties, and energy transfer of Tb ³⁺ –Sm ³⁺ –Yb ³⁺ tri-doped lithium–niobium–tellurite glass for applications in color display devices and WLEDs

A TeO₂-Nb₂O₅-LiO₂-CaO (TNLC) lithium-niobium-tellurite glass single-doped and co-doped with Tb³⁺, Sm³⁺, and Yb³⁺ ions was synthesized <i>via</i> a conventional melt-quenching method. The Tb³⁺-Sm³⁺ co-doped TNLC glass could be tuned to emit white light effectively by controlling the ratio of Tb³⁺ and Sm³⁺ in the glass. The fluorescence lifetime of the Tb³⁺-Sm³⁺ co-doped TNLC glass indicated the existence of multiple energy transfer channels, including from Tb³⁺ to Sm³⁺ ions and the reverse energy transfer from Sm³⁺ to Tb³⁺ ions. Taking advantage of these energy transfer channels, the color coordinates of the material could be changed from yellowish-pink and yellowish-green emissions to white emission by controlling the ratio of ions doped in TNLC glasses. The optimal molar concentration ratio between Tb³⁺ and Sm³⁺ ions for the best white light emission was 0.83 for the TNLC-0.5Tb0.6Sm sample. Changing the ratio of these rare-earth (RE) ions allowed tuning the color temperature of the material from 5616 to 7699 K. Thus, Tb³⁺-Sm³⁺ co-doped and Tb³⁺-Sm³⁺-Yb³⁺ tri-doped TNLC glasses are promising materials for color display applications and white light-emitting diodes (WLEDs).