Photoluminescence Investigations of Dy(3+)-Doped Silicate Xerogels and SiO(2)-LaF(3) Nano-Glass-Ceramic Materials

In this work, the series of Dy(3+)-doped silicate xerogels were synthesized by sol-gel technique and further processed at 350 °C into SiO(2)-LaF(3):Dy(3+) nano-glass-ceramic materials. The X-ray diffraction (XRD) measurements, along with the thermal analysis, indicated that heat-treatment triggered the decomposition of La(TFA)(3) inside amorphous sol-gel hosts, resulting in the formation of hexagonal LaF(3) phase with average crystal size at about ~10 nm. Based on the photoluminescence results, it was proven that the intensities of blue ((4)F(9/2) → (6)H(15/2)), yellow ((4)F(9/2) → (6)H(13/2)), and red ((4)F(9/2) → (6)H(11/2)) emissions, as well as the calculated yellow-to-blue (Y/B) ratios, are dependent on the nature of fabricated materials, and from fixed La(3+):Dy(3+) molar ratios. For xerogels, the emission was gradually increased, and the τ((4)F(9/2)) lifetimes were elongated to 42.7 ± 0.3 μs (La(3+):Dy(3+) = 0.82:0.18), however, for the sample with the lowest La(3+):Dy(3+) molar ratio (0.70:0.30), the concentration quenching was observed. For SiO(2)-LaF(3):Dy(3+) nano-glass-ceramics, the concentration quenching effect was more visible than for xerogels and started from the sample with the highest La(3+):Dy(3+) molar ratio (0.988:0.012), thus the τ((4)F(9/2)) lifetimes became shorter from 1731.5 ± 5.7 up to 119.8 ± 0.4 μs. The optical results suggest, along with an interpretation of XRD data, that Dy(3+) ions were partially entered inside LaF(3) phase, resulting in the shortening of Dy(3+)-Dy(3+) inter-ionic distances.