Absolute quantum yield(Φ) is one of the most important parameters to evaluate the potential of novel materials.Lanthanide complexes Eu_xGd_(1-x)(TTA)3phens are synthesized with the ratio of Gd~(3+) dopant concentration ranging from 10%to 90%to improve the absolute quantum yield.Eu_xGd_(1-x)(TTA)_3phens possess similar infrared and ultraviolet spectra,showing that they have similar molecular structures.The absolute emission quantum yields of Eu_xGd_(1-x)(TTA)_3phens are determined using a fluoromax-4spectrofluorometer equipped with an integrating sphere.The fluorescence lifetimes of the Eu_xGd_(1-x)(TTA)_3phens are measured in the same experiment.It was found that both absolute quantum yields and fluorescence lifetimes of Eu_xGd_(1-x)(TTA)_3phens are of quasi-periodic variation with the change of the Gd~(3+)dopant concentrations.The absolute quantum efficiency and fluorescence lifetime vary with respect to the Gd content in an opposite fashion,indicating that the rate of energy absorption by the Eu_xGd_(1-x)(TTA)_3phens and the conversion to light energy is critical for the absolute quantum efficiency.The radiative rate constant K_r and non-radiative rate constant K_(nr) are calculated.The dependence of K_r and K_(nr) on the Gd~(3+) dopant concentrations is very similar to that of absolute quantum efficiency.The radiation rate constant K_r and absolute quantum efficiency have a linear relationship. Absolute quantum yield (Φ) is one of the most important parameters to evaluate the potential of novel materials. Lanthanide complexes Eu_xGd_ (1-x) (TTA) 3phens are synthesized with the ratio of Gd ~ (3+) dopant concentration ranging from 10 % to 90% to improve the absolute quantum yield. Eu_xGd_ (1-x) (TTA) _3phens possess similar infrared and ultraviolet spectra, showing that they have similar molecular structures. The absolute emission quantum yields of Eu_xGd_ (1-x) (TTA ) _3phens are determined using a fluoromax-4 spectrofluorometer equipped with an integrating sphere. The fluorescence lifetimes of the Eu_xGd_ (1-x) (TTA) _3phens are measured in the same experiment. It was found that both absolute quantum yield and fluorescence lifetimes of Eu_xGd_ (1-x) (TTA) _3phens are of quasi-periodic variation with the change of the Gd ~ (3+) dopant concentrations. The absolute quantum efficiency and fluorescence lifetime vary with respect to the Gd content in an opposite fashion, indicating that the rate of energy absorpt ion by the Eu_xGd_ (1-x) (TTA) _3phens and the conversion to light energy is critical for the absolute quantum efficiency. The radiative rate constant K_r and the non-radiative rate constant K_ (nr) are calculated. dependence of K_r and K_ (nr) on the Gd ~ (3+) dopant concentrations is very similar to that of absolute quantum efficiency. The radiation rate constant K_r and absolute quantum efficiency have a linear relationship.