Search for D-level emission of Pb 2+ in alkaline-earth aluminates and gallates

The luminescence properties of the Pb 2+ ion in compounds AB2O4 (A = Sr 2+, Ba 2+; B = Al 3+, Ga 3+) with the tridymite structure and compounds AB12O19 (A = Sr 2+, Pb 2+; B = Al 3+, Ga 3+) with the magnetoplumbite structure are investigated. As a consequence of the two different sites in the tridymites, two emission bands due to the 3P0 → 1S0 ( A band) transition on the Pb 2+ 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 Pb 2+ compositions do not show a significant thermal barrier between the A and D levels; this is tentatively ascribed to the higher covalency of these compositions.