Synthesis, characterization and fluorescence study of Eu(III) tungstates and molybdates

A new tungstate Na8WO7·2H2O and molybdate compound (NH4)6Mo7O24·4H2O are used, respectively, as precursors to the preparation (in aqueous solutions and at room temperature) of Eu8(WO7)3·5H2O and Eu2Mo7O24·4H2O, respectively. It is verified that the emission intensity of the 5D0 → 7F2 bands is higher (about three times) to Eu2Mo7O24·4H2O in comparison to Eu8(WO7)3·5H2O. From the obtained X-ray powders’ diffraction patterns is concluded that Na8WO7·2H2O and Eu8(WO7)3·5H2O are isomorphs. Furthermore, it is inferred that Eu2Mo7O24·4H2O exhibits a structure similar to that of Eu8(WO7)3·5H2O. Furthermore, it is verified that the anhydrous Na8WO7 is stable in the 105–550 °C range, Eu8(WO7)3 in the 110–350°C range and Eu2Mo7O24 in the 350–720 °C range.