Effect of codopants on enhanced luminescence of GdTaO4 : Eu3+ phosphors

(Gd0.92−xMx)TaO4:Eu0.08 (M=Li+, Na+,K+,Mg2+,Zn2+,Ca2+,Ba2+,Al3+) phosphors were synthesized by conventional solid-state reaction. The effect of codoping M ions on enhanced photoluminescence (PL) of GdTaO4:Eu3+ was investigated. It was found that the improvement of PL intensity was closely related to the effective ionic radius of codopant and the mismatch in Pauling’s electronegativity between codopant and Gd. The PL intensity of GdTaO4:Eu3+ phosphor was improved evidently by codoping with Li+,Mg2+,Zn2+, or Al3+ whose radius is less than that of Gd3+, and hardly with Na+,K+,Ca2+, or Ba2+ whose radius is larger than that of Gd3+. Meanwhile, the intensity increased with the electronegativity mismatch for codoping with Li+,Mg2+,Zn2+, or Al3+. It was proposed that the effect of codopants on enhanced luminescence was mainly regarded as the result of a suitable local distortion of crystal field surrounding the Eu3+ activator. These results will play an important role in seeking some more effective codopants.