Eu2+ Luminescence in Hexagonal Aluminates Containing Large Divalent or Trivalent Cations

Abstract

The Eu2+ luminescence in hexagonal aluminates containing large divalent or trivalent cations was studied in relation to the crystal structures of the host lattices. It was found that these can be divided into three groups: compounds with the magnetoplumbite structure like ; the La‐containing aluminates ( and ) which have a structure quite close to magnetoplumbite; and phases with the β‐alumina structure like and . In the first type of host lattice, the Eu2+ luminescence is at a relatively short wavelength, in the last group at relatively long wavelength. The La aluminates doped with Eu2+ take an intermediary position in this respect. The existence of various types of host lattices is also reflected in the shape and the position of the excitation spectra of the Eu2+ luminescence. Their complicated shapes allow only a qualitative discussion of the position of the excited 5d levels of the Eu2+ ion. The quantum efficiency of the luminescence was found in most cases to be high. The temperature dependence curves of the intensity of the Eu2+ luminescence can be divided into two groups: those of the magnetoplumbite (like) phosphors and those of the β‐alumina type phosphors. The experimental quenching temperatures are discussed in relation to a model proposed by Blasse and Bril.