Upconversion properties of Gd-based ceramics, attached into polystyrene films

Tm³⁺- and Yb³⁺-doped lithium-gadolinium oxide (Li-Gd2O3) ceramics, prepared by the simple evaporation technique, were incorporated into polystyrene (PS) films (as recycled Styrofoam). A study of the upconversion (UC) emission from Tm³⁺ as well as Yb³⁺ ions was performed under continuous wave excitation of a 980-nm laser, for both powder and PS film samples. High-intensity light emissions (UC) were observed at 476, 488, and 665 nm, associated with inter electronic energy state transitions of the Tm³⁺ ion, from ¹D2 to ³F4, ¹G4 to ³H6, and ³F3 to ³H6, respectively. Yb³⁺ presence makes possible the thulium blue emission in the UC luminescence because it acts as a sensitizer under 980-nm excitation. Lithium is used as part of the host lattice (Lix-Gd2-xO3; 0 ≤ x ≥ 1) in order to achieve a greater crystallinity as Li⁺ acts as fluxing agent. The PS films remain highly transparent in the light’s visible region even after the incorporation of the ceramic particles (around 80% T).