Yolk-shell structured Y₂O₃:Eu³⁺ phosphor powders with enhanced photoluminescence properties prepared by spray pyrolysis

Highly crystalline Y₂O₃:Eu³⁺ yolk-shell phosphor powders with enhanced photoluminescence intensity are successfully prepared by spray pyrolysis. The Y₂O₃:Eu³⁺ yolk-shell powder is formed directly from each droplet containing yttrium and europium salts and sucrose inside a hot-wall reactor that is maintained at 900 °C. The yolk-shell structure of the phosphor powder is maintained even at a high post-treatment temperature of 1200 °C, exhibiting the maximum photoluminescence intensity. For comparison, a spherical shape Y ₂O₃:Eu³⁺ phosphor powder is also prepared by the same procedure but without sucrose during spray pyrolysis. The photoluminescence intensity of the Y₂O₃:Eu³⁺ yolk-shell powder is 171% of that of the spherical shape phosphor powder at a post-treatment temperature of 1200 °C. The morphological advantage of a yolk-shell phosphor powder with a core@void@shell configuration inducing higher absorption of excitation light in the structure is attributed to multiple light-reflecting and light-scattering in the interstitial void between the core and the shell.