ALBERT

Description: Highly transparent (Y 0.95− x Gd x Eu 0.05 ) 2 O 3 ( x  =   0.15–0.55) ceramics have been fabricated by vacuum sintering at the relatively low temperature of 1700°C for 4 h with the in-line transmittances of 73.6%–79.5% at the Eu 3+ emission wavelength of 613 nm (~91.9%–99.3% of the theoretical transmittance of Y 1.34 Gd 0.6 Eu 0.06 O 3 single crystal), whereas the x  =   0.65 ceramic undergoes a phase transformation at 1650°C and has a transparency of 53.4% at the lower sintering temperature of 1625°C. The effects of Gd 3+ substitution for Y 3+ on the particle characteristics, sintering kinetics, and optical performances of the materials were systematically studied. The results show that (1) calcining the layered rare-earth hydroxide precursors of the ternary Y–Gd–Eu system yielded rounded oxide particles with greatly reduced hard agglomeration and the particle/crystallite size slightly decreases along with increasing Gd 3+ incorporation; (2) in the temperature range 1100°C–1480°C, the sintering kinetics of (Y 0.95− x Gd x Eu 0.05 ) 2 O 3 is mainly controlled by grain-boundary diffusion with similar activation energies of ~230 kJ/mol; (3) Gd 3+ addition promotes grain growth and densification in the temperature range 1100°C–1400°C; (4) the bandgap energies of the (Y 0.95− x Gd x Eu 0.05 ) 2 O 3 ceramics generally decrease with increasing x ; however, they are much lower than those of the oxide powders; (5) both the oxide powders and the transparent ceramics exhibit the typical red emission of Eu 3+ at ~613 nm (the 5 D 0 7 F 2 transition) under charge transfer (CT) excitation. Gd 3+ incorporation enhances the photoluminescence and shortens the fluorescence lifetime of Eu 3+ .