Fabrication and upconversion luminescence of novel transparent Er2O3 ceramics

Transparent Er 2 O 3 ceramics were successfully fabricated via vacuum sintering for the first time, using low-temperature synthetic layered rare-earth hydroxide (LRH) as the precursor. The LRH exhibits single crystal structure and characteristic two-dimensional nanosheet morphology with a thickness of only ∼10 nm. Calcining the LRH precursor at optimum temperature of 1000 °C yields a rounded fine oxide powder with an average particle size of ∼35 nm and relatively uniform size distribution. With the sinterable oxide particle , the vacuum sintered Er 2 O 3 ceramic has a relatively high transparency of ∼80 % at around 5.4 μm (∼99 % of the theoretical value) and an average grain size of ∼55 μm. Under 980 nm laser excitation, the Er 2 O 3 ceramic displays strong red emission at ∼654‒685 nm and weak green emission at ∼553‒565 nm arising from 4 F 9/2 → 4 I 15/2 and 4 S 3/2 / 2 H 11/2 → 4 I 15/2 transitions, respectively. The intensities of red and green emissions rise along with increasing laser output powers, the upconversion mechanisms of which are both attributable to two-phonon processes. The CIE chromaticity diagrams move towards cooler tone from yellow to greenish-yellow colours with enhanced output powers. The lifetimes of the Er 2 O 3 ceramic were determined to be ∼13.0 and 8.4 μs for the 684 and 565 nm emissions, respectively.