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

A new tungstate Na 8WO 7·2H 2O and molybdate compound (NH 4) 6Mo 7O 24·4H 2O are used, respectively, as precursors to the preparation (in aqueous solutions and at room temperature) of Eu 8(WO 7) 3·5H 2O and Eu 2Mo 7O 24·4H 2O, respectively. It is verified that the emission intensity of the 5D 0 → 7F 2 bands is higher (about three times) to Eu 2Mo 7O 24·4H 2O in comparison to Eu 8(WO 7) 3·5H 2O. From the obtained X-ray powders’ diffraction patterns is concluded that Na 8WO 7·2H 2O and Eu 8(WO 7) 3·5H 2O are isomorphs. Furthermore, it is inferred that Eu 2Mo 7O 24·4H 2O exhibits a structure similar to that of Eu 8(WO 7) 3·5H 2O. Furthermore, it is verified that the anhydrous Na 8WO 7 is stable in the 105–550 °C range, Eu 8(WO 7) 3 in the 110–350°C range and Eu 2Mo 7O 24 in the 350–720 °C range.