Investigation of Eu 3+ sites in SrLaGa 3O 7, SrLaGaO 4 and SrLaAlO 4 crystals

Abstract

Trivalent europium has been used as a probe of symmetry of crystalline sites occupied by rare earth ions and of electron-phonon coupling in crystals belonging to two wide families of compounds with general chemical formulae ABCO 4 and ABC 3O 7 ( A = Ca, Sr; B = Y, La- Gd; C = Al, Ga). Random distribution of crystallochemically different ions over the lattice sites results in the spread of energy of Eu 3+ excited states in the three matrices, but the site symmetry is preserved in SrLaAlO 4 and SrLaGaO 4. Strongly perturbed sites behave as one quasicentre with single decay time of luminescence. The multiphonon relaxation rates for the 5D 2 level of Eu 3+ have been analysed with a point charge nonlinear relaxation mechanism proposed recently. Unusually low electron-phonon coupling in SrLaGaO 4:Eu 3+ system has been found.