INVESTIGATION OF EU3+ SITES IN SRLAGA3O7, SRLAGAO4 AND SRLAALO4 CRYSTALS

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 chem ical formulae ABCO(4) and ABC(3)O(7) (A = Ca,Sr; B = Y, La- Gd; C = AI ,Ga). Random distribution of crystallochemically different ions over t he lattice sites results in the spread of energy of Eu3+ excited state s in the three matrices, but the site symmetry is preserved in SrLaAlO 4 and SrLaGaO4. Strongly perturbed sites behave as one quasicentre wit h single decay time of luminescence. The multiphonon relaxation rates for the D-5(2) level of Eu3+ have been analysed with a point charge no nlinear relaxation mechanism proposed recently. Unusually low electron -phonon coupling in SrLaGaO4:Eu3+ system has been found. (C) 1997 Else vier Science Ltd.