Abstract: (Y_1-x-y Gd_xCe_y) BO₃ and (La_1-x-yGd_xCe_yMg)B₅O₁₀ are different in structure and havebeen synthesized by solid state reactions.Their spectroscopic properties have been studied.The energy transfer between Ce³⁺ and Gd³⁺ in different borate matrix is quite different.In(Y_1-x-yGd_xCe_y)BO₃ the 5d state of Ce³⁺ lies lower in energy than ⁶I and ⁶P levels of the Gd³⁺, so Gd³⁺ in its excited state can thansfer its energy to Ce³⁺; whereas in(La_1-x-yGd_xCe_y Mg)B₅O₁₀ the 5d state of Ce³⁺ lies higher in energy than ⁶I and ⁶P levels of Gd³⁺ andvery close to ⁶I, the main excited state of Gd³⁺, hence Ce³⁺ can effectively transfer itsexcited energy to Gd³⁺.Accordingly, the energy transfer between Ce³⁺ and Gd³⁺ is mainlydetermined by the position of Ce³⁺ enrgy levels in different hosts.

Key words: Ce³⁺, Gd³⁺luminescence, rare aarth borate, energy transfer