Optical investigation of Eu3+:PbF2 ceramics and transparent glass-ceramics

This paper reports an optical investigation of glass-ceramics formed by annealing glasses with compositions 50 GeO2-40 PbO-10 PbF2-x EuF3, x = [0.5; 1:1.5; 2] and polycrystalline ceramics with composition 100 PbF2, y EuF3, with y = 5, 10, 15 and 20. For each material, the photoluminescence spectrum and the photoluminescence lifetimes of the D-5(0), D-5(1) and D-5(2) EU3+ levels are measured. Occurrence of Eu3+:beta-PbF2 nanocrystallites in the glass-ceramics is confirmed and total ceramisation requires more than 10% of EuF3 with respect to PbF2 in the starting glass. In the Eu3+:beta-PbF2 ceramics and glass-ceramics, Eu3+ ions replace Pb2+ in their regular cubic site, but they interact together to form dimers and higher nuclearity clusters. These two species are easily distinguished according to their photoluminescence decay rate. For the EuF3 rates investigated here, there are no isolated Eu3+ ions in the PbF2 lattice. A preliminary investigation of the optical properties of co-doped Gd3+:Eu3+:beta-PbF2 ceramics was also performed. It shows that mixed Gd3+-Eu3+ dimers and clusters are formed, and that efficient Gd3+ -> Eu3+ energy transfer occurs in these ceramics. The Pb2+ ions of the lattice may also be involved in the energy transfer process. (C) 2011 Elsevier B.V. All rights reserved.