Fully concentrated Eu3+ based oxalate Eu-2(C2O4)(3)center dot 10H(2)O phosphor has been successfully synthesized by an efficient surfactant-free hydrothermal method directly without further sintering treatment. The techniques of XRD, TG-DTA, FT-IR, SEM, EDS and PL were employed to characterize the as-obtained products. It was found that in the temperature range of 100-150 degrees C, all samples were well crystallized with monoclinic structures. And the best purity of the samples produced was achieved when the temperature is 150 degrees C. The possible formation mechanisms for Eu-2(C2O4)(3)center dot 10H(2)O with different structures were put forward. The Eu-2(C2O4)(3)center dot 10H(2)O phosphors can be effectively excited by 396 nm light, and exhibit strong red emission around 619 nm, attributed to the Eu3+ D-5(0) -> F-7(2) transition. A detailed investigation on the fluorescence of products revealed that the luminescence properties are strongly correlated with the crystallinities, morphologies and sizes. (C) 2014 Elsevier Ltd. All rights reserved.