The luminescence spectra of Eu3+ doped in a series of double perovskite lattices Ba(2)LnMO(6) (Ln = Y, Gd; M = Nb, To) have been recorded at room temperature and 10 K. Together with FT-IR and FT-Raman spectra and aided by DFT vibrational energy calculations, assignments have been made for the crystal field levels of the D-5(J) (J = 0,1) and F-2(J) (J = 0-2) multiplets. The luminescence spectra are consistent with monoclinic symmetry of these systems. The crystal field parameters from the fitting of the energy level data set of Ba2YNbO6:Eu3+ enable the crystal field strength to be calculated, and the order of magnitude is Cl- < O2- < F- for the EuX6n- (n = 6 for halogen, 9 for oxide) moieties. For these systems, an empirical linear relationship between crystal field strength and electronegativity of ligand X has been found. By contrast, the nephelauxetic series from the depression of the Slater parameter F-2 is Cl- approximate to O2- > F- > free ion for these systems.