Abstract:Red-emission (Y_0.95Eu_0.05)₂O₃ submicron spheres and microplates were selectively obtained via hydrothermal precursor synthesis (150 °C, 12 h) followed by calcination at 1000 °C. Characterizations of the products were carried out by combined means of XRD, FT-IR, FE-SEM and PL analysis. The precursors could be modulated from basic-carbonate submicron spheres to normal carbonate microplates by increasing the molar ratio of urea to Y+Eu from 10 to 40-100. The resultant oxides largely retain their respective precursor morphologies at 1000 °C, but morphology confined crystal growth was observed for the microplates, yielding more enhanced exposure of the (400) facets. Both the (Y_0.95Eu_0.05)₂O₃ spheres and microplates exhibit nearly identical positions of the PL bands and similar asymmetry factors of luminescence [I(⁵D₀→⁷F₂)/I(⁵D₀→⁷F₁), ~11] under 250 nm excitation, but the microplates show a significantly strong red emission at ~613 nm (~1.33 times that of the spheres) owing to their larger particle size and denser packing of primary phosphor crystallites.

Key words: optical material; powder processing; morphology-dependent physical phenomena; rare earths; optical spectroscopy