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

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 C_2v 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.