Fluorescence enhancement and structural development of sol-gel derived Er³⁺-doped SiO₂ by yttrium codoping

Er³⁺-Y³⁺ codoped SiO₂ powdered bulks were prepared by a sol-gel process. The effect of Y³⁺ codoping on the fluorescence properties and structural development of Er³⁺-doped SiO₂ is investigated. The maximum 1.54 μm photoluminescence (PL) intensity occurs in the sample with Er³⁺ (10 mol%)-Y³⁺ (50 mol%) codoped and annealed at 985°C. This can be attributed to the competition between the content of hydroxy groups and Er site symmetry. Improvement of optimum PL properties due to Y³⁺ codoping by a factor of ∼20 for intensity and 1.8 for the full width at half maximum (57 nm) was obtained in comparison with the Er³⁺-doped SiO₂ system. Extended X-ray absorption fine structure analysis shows that the local chemical environment of Er³⁺ ions in the Er³⁺-Y³⁺ codoped SiO₂ is similar to that in Er₂O₃. The average spatial distance between Er³⁺ ions is enlarged due to a partial substitution of Y³⁺ for Er³⁺ ions in the Er₂O₃-like local structure, which results in a reduction of the concentration quenching effect.