Site selective spectroscopy and crystal field analysis of Eu3+ doped lanthanum–calcium–zirconium–silicon borate

Abstract

The fluorescence of Eu3+ doped lanthanum–calcium–zirconium–silicon borate ceramic was studied at 77 and 300 K using laser excited site selective spectroscopy. The fluorescence spectrum excited at 514.532 nm reveals the presence of three distinct sites for Eu3+. The sites were assigned to Eu3+ substituting for lanthanum in a ninefold coordination site in LaBO3 and Eu3+ substituting for Ca2+ in six- and sevenfold coordination sites in Ca2B2O5. To assign the spectra to the definite sites a phenomenological crystal field analysis was conducted, using C2v symmetry. The crystal field for Eu3+ in Ca2B2O5 was found to be dominated by electrostatic effects. The large 7F1 level splitting and the value of the B20 parameter support the concept of strong ionic bonding between europium and oxygen in Ca2B2O5.