Search for D-level emission of Pb2+ in alkaline-earth aluminates and gallates

The luminescence of the Pb2+ ion in compounds AB(2)O(4) (A = Sr2+, Ba2+; B = Al3+, Ga3+) with the tridymite structure and compounds AB(12)O(19) (A = Sr2+, Pb2+; B = Al3+, Ga3+) with the magnetoplumbite structure are investigated. As a consequence of the two different sites in the tridymites, two emission bands due to the P-3(0) --> S-1(0) (A band) transition on the Pb2+ ion are observed in compositions with this structure. Additionally, an emission band with a much larger Stokes shift is found in the tridymites as well as in the magnetoplumbites, which is attributed to a transition from a higher lever, the so-called D-level. The gallate lattices as well as the undiluted Pb2+ compositions dod not show a significant thermal barrier between the A and D levels; this is tentatively ascribed to the higher covalency of these compositions.