Line broadening and crystallographic sites for Eu3+ in disordered double borate Ca3Gd2(BO3)4

• The line broadening properties of Ca3Gd2(BO3)4: Eu3+ are investigated.
• Three types of substitution sites for Eu3+ are identified in Ca3Gd2(BO3)4.
• The crystal-field parameters are calculated from the 7FJ levels.
• The larger distribution of M-O distances gives higher crystal-field strength on Eu3+.

The samples of Eu3+-doped Ca3Gd2(BO3)4 were synthesized by solid-state reaction. Line broadening and site-substitution properties of Eu3+ in Ca3Gd2(BO3)4 are investigated by the site-selective laser-excitation spectroscopy. Three excitation lines corresponding to the three crystallographic sites are observed in the excitation spectra of the 7F0 → 5D0 transition. The spectral lines in the excitation and emission spectra of Ca3Gd2(BO3)4:Eu3+ are much broader than those in usual crystalline lattices which are attributable to the structural disorder of the Ca3Gd2(BO3)4 lattice. Crystal-field splittings of three types of Eu3+ in Ca3Gd2(BO3)4 are determined from selectively excited emission spectra. The crystal-field parameters and crystal-field strength parameters are calculated with the values of experimentally obtained 5D0 and 7FJ energy levels. The results are discussed in relation with the distribution of the substitution sites for Eu3+ in Ca3Gd2(BO3)4.