The Upconversion Luminescence Of Rare-earth Ions In Oxy-fluoride Glasses And Ceramics

Rare-earth (RE) doped materials are extensively used for all-solid-state short-wavelength lasers, three dimensional display and anti-fake labels et al, due to the fact that the RE doped materials can convert un-visible infrared and ultraviolet light into the visible light. In this paper, the RE doped materials having the property of converting the infrared into visible light, i.e., upconversion luminescence materials, were studied. The entire work could be distributed into two parts: in the first part, the effects of materials'chemical composition on the luminescence efficiency of the samples were discussed in detail. The Er³⁺ doped oxyfluoride glasses with different matrix compositions were synthesized and corresponding optical measurements were carried out, including absorption spectra, Raman scattering and upconversion luminescence. On basis of the above measurements, the influence of the composition on the absorption and emission properties of Er³⁺ and the phonon energy of the matrix was analyzed. Subsequently, the role of the phonons in the upconversion process was discussed specially. It was found that the ratio of the red to green emission (r(i)) of the low concentration of Er³⁺ doped samples was not influenced by the phonon energy under the 980 nm LD excitation. However, the value of r(i ) increased with the increase of the phonon energy in Er³⁺/Yb³⁺ codoped glasses which indicated that the emissions of this kind of material were influenced remarkably by the phonon. It was also found that the red emission was enhanced hundreds of times, which means that the Er³⁺/Yb³⁺ codoped materials have the potential as the high-efficiency red emission materials. In the second part, i.e., chapter 4, the influence of microstructure on the upconversion luminescence of RE ions was studied. The microstructure was affected by many conditions, e.g., the uniformity of the solid-state reaction, the speed of cooling and the annealing. In this part, the relationship between the microstructure and the luminescence was researched by the SEM and XRD. It was confirmed that the formation of the Pb2F2O dendrite is beneficiary to the increase of the emission intensity of Ho³⁺ in Ho³⁺ doped 20GeO₂-80PbF₂ ceramics. The overall emission intensity of Er³⁺, especially the red emission, was enhanced greatly which is ascribed to the precipitating ofβ-PbF₂ crystals in Er³⁺ doped 50GeO₂-50PbF₂ glasses. The work in the second part is useful for the synthesis of the anti-fake and the phosphor materials, and the study of relationship between the luminescence and microstructure of RE doped materials.