Synthesis, electrical properties, and optical characterization of Eu3+-doped La2Mo2O9 nanocrystalline phosphors

The lanthanum molybdate phosphor, La2Mo2O9, is a new fast ionic conductor that has shown potential uses as a nanocrystalline matrix for optically active lanthanide ions. Eu3+-doped La2Mo2O9 phosphors were prepared from freeze-dried powder precursor and the nano-polycrystalline powders obtained were characterized by XRD, DSC, TG/DTA, SEM, impedance spectroscopy, and optical spectroscopy. The substitution of La3+ by Eu3+ in La2-xEuxMo2O9 suppresses partially the phase transition observed in the undoped samples and increases both the density of sintered pellets and the ionic conductivity. Polycrystalline powder and sintered pellets of La2Mo2O9 phosphor exhibits optical transitions in the UV-visible region at low temperature, although there is a luminescence quenching process with temperature. At room temperature orange and red emissions are only observed when doping with Eu3+ ions. Moreover, a nanocrystal-size dependent energy transfer process from the matrix to the Eu3+ ions occurs. (C) 2004 Elsevier B.V. All rights reserved.