Lead fluoride β-PbF2 nanocrystals containing Eu3+ and Tb3+ ions embedded in sol-gel materials: Thermal, structural and optical investigations.

Nanocrystalline β-PbF 2 phase singly-doped with Eu 3+ and Tb 3+ ions have been successfully synthesized using sol-gel technique and subsequent heat-treatment of xerogels at 350 °C. Thermal behavior and structural properties of obtained materials were studied using thermogravimetric analysis (TG), differential scanning calorimetry (DSC) as well as FT-IR and Raman techniques. XRD results confirmed formation of β-PbF 2 nanocrystals embedded in silica amorphous hosts after annealing at 350 °C. Moreover, the photoluminescence properties have been investigated based on excitation and emission spectra as well as decay analysis from the 5 D 0 (Eu 3+ ) and the 5 D 4 (Tb 3+ ) excited states. The sharp intraconfigurational 4f 6 −4f 6 and 4f 8 −4f 8 emission transitions assigned as the 5 D 0 → 7 F J (J=0–4) of Eu 3+ and the 5 D 4 → 7 F J (J=6-3) of Tb 3+ bands, respectively, were registered. The most prominent bands in studied xerogels and glass-ceramic materials are related to the following electronic transitions: 5 D 0 → 7 F 1 (orange) and 5 D 0 → 7 F 2 (red) (Eu 3+ ) as well as 5 D 4 → 7 F 5 (green) and 5 D 4 → 7 F 6 (blue) (Tb 3+ ). Thus, the R/O (Eu 3+ ) and G/B (Tb 3+ ) luminescence intensity ratios were calculated and analyzed. Luminescence decay kinetic clearly indicated a presence of two different surroundings around Eu 3+ and Tb 3+ dopants in β-PbF 2 -based glass-ceramic samples. In such singly-doped with Eu 3+ and Tb 3+ materials, the longer luminescence lifetimes (Eu 3+ : τ 1 ( 5 D 0 )=0.90 ms, τ 2 ( 5 D 0 )=5.15 ms; Tb 3+ : τ 1 ( 5 D 4 )=0.48 ms, τ 2 ( 5 D 4 )=4.01 ms) of an appropriate excited states were achieved in comparison to xerogel hosts (Eu 3+ : τ( 5 D 0 )=0.38 ms; Tb 3+ : τ( 5 D 4 )=0.49 ms). The obtained results indicate the incorporation of Eu 3+ and Tb 3+ ions into nanocrystalline phase during ceramization process. [ABSTRACT FROM AUTHOR]