Replication of wood into biomorphous nanocrystalline Y2O3:Eu3+ phosphor materials

Biomorphous Eu3+-doped Y2O3 was fabricated by replication of wood templates using vacuum-assisted infiltration of a water-based sol-gel mixture and subsequent calcination at 750A degrees C. The precursor sols were prepared from (Y0.95Eu0.05)(2)O-3 dissolved in 10 vol% nitric acid and adding citric acid as the chelating agent. X-ray powder diffraction analyses and Rietveld refinements confirmed that the calcined samples were solely composed of bixbyite Y2O3:Eu3+ phase with a mean crystallite size of 16 nm. Scanning electron micrographs and cathodoluminescence imaging showed that the cellular preform anatomy was retained and that the original wood cell walls were completely transformed into phosphor struts with pore sizes ranging from 5 to 20 mu m. The optical properties of the biomorphous phosphor materials were analyzed by photoluminescence spectroscopy and assigned to the characteristic Eu3+ (4f(6) -> 4f(6)) electric dipole or magnetic dipole transitions. From fluorescence lifetime measurements, the mean lifetime was calculated as 1.62 ms.