文摘
The phosphor powders prepared by calcining mixtures (1:1, 1:2, and 1:3 mol ratios) of Eup>3+p>-doped lanthanum(III) hydroxycarbonate (LaCO3OH:Eup>3+p>) and δ-alumina (δ-Al2O3) powders under a mixed gas flow of H2 and N2 exhibited orange (593 and 617 nm) and blue (441 nm) emission peaks, which were associated with Eup>3+p>-doped lanthanum aluminate (LaAlO3:Eup>3+p>) and Eup>2+p>-doped lanthanum hexaaluminate (La0.827Al11.9O19.09:Eup>2+p>) phosphors, respectively. The relative amount of the latter phosphor increased with increasing reaction temperature and relative amount of δ-Al2O3 in the mixture. The conclusion that the blue emission is not associated with LaAlO3:Eup>2+p> but La0.827Al11.9O19.09:Eup>2+p> was supported by the following experimental results: the reduction of LaAlO3:Eup>3+p> did not give a blue emission; Eup>2+p> ions occupied more than one site in the host; the line shape and position of the blue emission band were close to those of the single La0.827Al11.9O19.09:Eup>2+p> phase. No formation of LaAlO3:Eup>2+p> might be due to the increase in the ionic radius caused by the reduction of Eup>3+p> to Eup>2+p>.