EPR and optical investigation of europium doped Ba12F19Cl5

Single crystals of the new host Ba12F19Cl5 doped with Eu2+ were grown and s tudied by electron paramagnetic resonance (EPR) and luminescence emission s pectroscopy. Three different Eu2+ sites were observed. Two of them had orth orhombic point symmetry while the last one was monoclinic. Physico-chemical and symmetry arguments allowed us to establish correspondence between the different Eu2+ centres and the host cation lattice sites. All three centres presented in their ground state important crystal field splitting. The 80 K luminescence emission spectrum consisted of one broad unsymmetrical f-d b and peaking at 22 700 cm(-1). No 4f-4f transitions of the Eu2+ ion were obs erved between room temperature and 80 K.