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

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