Structural properties and visible emission of Eu3+-activated SiO2–ZnO–TiO2 powders prepared by a soft chemical process

Abstract In this work, the structural and optical properties of the 60SiO 2 –20ZnO–20TiO 2 system (in mol%) doped with 1 mol% of Eu 3+ were evaluated. Stable and transparent sols, homogeneous gels, and powders were prepared by a soft chemical process followed by annealing from 700 to 1100 °C. Visible emission was observed in the photoluminescence (PL) spectra from 570 to 700 nm owing to the Eu 3+ ions, with the most intense emission peaks at 614 and 590 nm related to the 5 D 0 → 7 F 2 and 5 D 0 → 7 F 1 transitions, corresponding to red (R) and orange (O) colors, respectively. The R/O intensity ratios between 3.16 and 3.73 were observed and correlated to the structural properties of the host. X-ray diffraction patterns indicated that the reduction of PL at 614 nm and changes in the R/O values were due to the crystallization process. In addition, the FTIR spectra showed a gradual decrease of the hydroxyl absorption bands around 3436 and 1640 cm −1 and an increase of the bands related to Ti–O–Ti and Si–O–Si linkages, indicating polymerization and densification process of the host was achieved above 700 °C. Moreover, increasing the annealing temperature resulted in the formation of ZnTiO 3 and Zn 2 TiO 4 crystalline phases, as well as rutile TiO 2 . Finally, intensity parameters ( Ω λ ), and quantum efficiency were calculated by applying Judd–Ofelt theory to Eu 3+ ions, which showed that the Eu 3+ -doped samples can be used in displays and LEDs.