Effect of non-stoichiometry on the luminescence of Eu2+ doped aluminates with the β-alumina-type crystal structure

In Al2O3 rich Ba-aluminate: Eu phosphors, a green luminescence band involving Eu is found next to the blue Eu2+-luminescence. The green band is ascribed to associates of Eu and oxygen ions at Ba sites. These Osub(Ba) ions also influence the concentration quenching behaviour of the Ba aluminate with high Eu content. The drop in the quantum efficiency of Ba-aluminate:Eu2+ on decreasing the Eu content of phosphors is not related to the presence of Osub(Ba). It is explained by the presence of Ba-vacancies. No green luminescence was observed in Mg-rich β-alumina type Eu2+ phosphors. Also, the quenching of the luminescence at higher Eu concentrations is less. Most probably, Mg2+ ions, positioned in between Osub(Ba) and Eu2+, block the interaction between last-named ions. (Auth.)