Effects of Lanthanum substitution on the luminescence properties and energy transfer mechanism of Gd_9.33(SiO₄)₆O₂:Ce polycrystalline

(Gd,La)_9.33(SiO₄)₆O₂:Ce polycrystalline powder with different proportion of Gd/La and Ce concentration was prepared by sol-gel technique, the crystal structure was confirmed by XRD, the luminescence properties were discussed under UV excitation. The energy transfer of Gd-Gd and Gd-Ce have been systematically investigated using luminescence spectra and there are three different types transfer mechanism for different Ce³⁺ and La³⁺ concentrations. The nonradiative energy transfer mechanism can switch from a short-range exchange mechanism to a longer-range dipole–dipole mechanism through energy migration between donors in heavily La substituted samples. The luminescence thermo-stability and activation energy were also measured and calculated. The luminescence properties and thermo-stability of Gd_9.33(SiO₄)₆O₂:Ce polycrystalline were improved, because of La³⁺ substitution which lead to the change of the energy transfer mechanism from Gd³⁺ to Ce³⁺