Luminescence in lanthanum chlorotungstate (LaWO4Cl)

The luminescence properties of LaWO4Cl are reported and discussed. The tungstate group occurs as a trigonal bipyramid. Although there is some analogy with the luminescence of the tetrahedral tungstate group, the small Stokes shift reveals the presence of five oxygen ions. The luminescence of the following ions was studied: Mo6+, Eu3+, Sm3+ and Tb3+. The molybdate group shows red emission with a larger Stokes shift than the tungstate group. Energy transfer from the tungstate group to the rare earth ions occurs over nearest-neighbor distances, except for Tb3+. Because of a low-lying f-d transition, the transfer efficiency is much higher for this ion