Fabrication and Characterization of Transparent (Y 0.98− x Tb 0.02 Eu x ) 2 O 3 Ceramics with Color‐Tailorable Emission

Transparent (Y 0.98− x Tb 0.02 Eu x ) 2 O 3 ( x  =   0–0.04) ceramics with color‐tailorable emission have been successfully fabricated by vacuum sintering at the relatively low temperature of 1700°C for 4 h. These ceramics have the in‐line transmittances of ~73%–76% at 613 nm, the wavelength of Eu 3+ emission (the 5 D 0 → 7 F 2 transition). Thermodynamic calculation indicates that the Tb 4+ ions in the starting oxide powder can essentially be reduced to Tb 3+ under ~10 −3  Pa (the pressure for vacuum sintering) when the temperature is above ~394°C. The photoluminescence excitation ( PLE ) spectra of the transparent (Y 0.98− x Tb 0.02 Eu x ) 2 O 3 ceramics exhibit one spin‐forbidden (high‐spin, HS ) band at ~323 nm and two spin‐allowed (low‐spin, LS ) bands at ~303 and 281 nm. Improved emissions were observed for both Eu 3+ and Tb 3+ by varying the excitation wavelength from 270 to 323 nm, without notably changing the color coordinates of the whole emission. The transparent (Y 0.98 Tb 0.02 ) 2 O 3 ceramic exhibits the typical green emission of Tb 3+ at 544 nm (the 5 D 4 → 7 F 5 transition). With increasing Eu 3+ incorporation, the emission color of the (Y 0.98− x Tb 0.02 Eu x ) 2 O 3 ceramics can be precisely tailored from yellowish‐green to reddish‐orange via the effective energy transfer from Tb 3+ to Eu 3+ under the excitation with the peak wavelength of the HS band. At the maximum Eu 3+ emission intensity ( x  =   0.02), the ceramic shows a high energy‐transfer efficiency of ~85.3%. The fluorescence lifetimes of both the 544 nm Tb 3+ and 613 nm Eu 3+ emissions were found to decrease with increasing Eu 3+ concentration.