Sol-gel derived erbium doped yttrium silicates

Yttria-silica gels were prepared through the sol-gel process. Gels of compositions (100-5x) SiO2-4xY2O3-xEr 2O3 (x = 0.05, 0.5, 1.0, 1.5, 2.0, 3.0 and 4.0), all in mole %, were prepared. Samples were designated SYEz, where z = 100--5x. Samples with co-doping ratios [Y3+]:[Er3+] equal to 4, 150 and 200 were prepared for a 0.05 mol.% Er2O3 composition. In addition, samples corresponding to nominal compositions of (Y/Er)2Si2O7 and (Y/Er)2SiO 5 were synthesized.;Dried gels were densified to glasses and glass-ceramics, through controlled heat treatment. Heat treatment schedules and densification temperatures were chosen based on thermal analyses (DTA, TGA). Phase-separation and crystallization were followed using X-Ray diffraction analysis on powders of heat-treated samples. Optical properties of the samples were studied by UV-VIS-NIR absorption, photo-luminescence (PL) and time-resolved spectroscopic techniques and were correlated with microstructure. Radiative and non-radiative properties of the densified samples at 1535 nm were studied by correlating the absorption and time-resolved spectral data with standard theoretical methods.;Samples with greater than 90 mol.% SiO2 densified to form transparent glasses before crystallization. Samples containing less than 90 mol.% SiO2 crystallized before densification. The tendency to crystallize depends on the total trivalent addition (Y2O3 + Er 2O3) and not on the ratio of Y:Er.;Samples containing the lowest trivalent content (SYE99-0.25 mol.%) remained amorphous up to 1200°C and produced the longest lifetime measured, 13.3 ms. No evidence for concentration quenching was observed. The highest value of PL quantum efficiency obtained was 73.1%.;In phase-separated samples, the PL decay lifetime increased with increasing Y:Er ratio and increasing temperature of heat treatment. After annealing at 1300°C, the lifetime measured for the highest Y:Er ratio of 200:1 (SYE89) was 10.0 ms and 3.3 ms for a ratio of 4:1 (SYE90). At high Y:Er ratios (>150:1), the main non-radiative decay mechanism is multi-phonon relaxation. Energy transfer mechanism becomes dominant as the ratio decreases (4:1). OH quenching is found to affect optical activity of Er ions in the amorphous phase.