Microstructure and luminescent properties of Eu2W2O9 phosphors

A homogeneous Eu2W2O9 phase with small grains (similar to 4.0 mu m) was formed for the specimens fired below 1175A degrees C. As the firing temperature was increased above 1150A degrees C, grain growth occurred and the grain shape changed from faceted to round. The excitation spectra of the Eu2W2O9 phosphor were similar to those of the Eu-2(WO4)(3) phosphor, but the absorption band due to the O2--> W6+ ligand to metal charge transfer was shifted to lower energies and the F-7(o)-> H-5(3) and F-7(o)-> F-5(2,4) transitions were not found. The intensity of the excitation and emission spectra of the Eu2W2O9 phosphor considerably increased with increasing firing temperature, due to the increased grain size and changed grain shape. The intensity of the red emission band of the Eu2W2O9 phosphor was higher than that of the Eu-2(WO4)(3) phosphor. Moreover, the addition of LiCl to the Eu2W2O9 phosphors considerably enhanced the intensity of their emission spectra, probably due to the increased grain size. Therefore, LiCl-added, Eu2W2O9 phosphor is a promising candidate material for red color emission.