Abstract
Preparation of Sr-aluminates in fine powder form, with Al/Sr ratio varying from 2 to 12 has been attempted by the hydrothermal method, starting from Al 2O 3.xH 2O gel containing europium and Sr(OH) 2 at 240 – 250°C. The products are annealed at 850 – 1150°C in N 2 + H 2 atmosphere to yield, efficient blue to green luminescent phosphors. The predominant phase isolated belongs to the family of ‘stuffed’ tridymite-nepheline structures, having the general formula, Sr n Al 2O 3+n where n ⩽ 1. With decreasing n-value, the relative intensity of the 405 nm emission band increases in preference to that of the 510 nm emission. The excitation spectra as well as the EPR results indicate the presence of Eu 2+ in the vacancy-associated nonequivalent sites. In presence of H 3BO 3 in the hydrothermal medium, aluminoborates such as SrAl 5BO 10, Sr 2Al 2B 2O 8 and Sr 3Al 6B 8O 24 are produced, whose only emission maximum around 400 nm remains as a band even at LN 2 temperature.
Published Version
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