SOLID-STATE CHEMISTRY OF POLYTUNGSTIC (POLYMOLYBDIC) ACIDS AND THEIR SALTS .3. EFFECTS OF DOPANT-SI, DOPANT-GE, DOPANT-SN, DOPANT-PB HYDRATION, AND REDUCTION ON THE PHOTOLUMINESCENCE OF NA5EU(MOO4)4

Doping Na5Eu(MoO4)4, which has a scheelite structure, results in an intensity increase of the intrinsic photoluminescence. In the emission spectra an extra emission peak appears in the narrow range of 616.2-616.5 nm throughout the SiGeSnPb dopant series. The increasing intensity of intrinsic photoluminescence seems to be connected to the covalent bonding strength of SiO, GeO, SnO, PbO. The appearance or disappearance of an extra peak may be explained in terms of a symmetry change of a local site of the Eu(III) ion. The emission intensity of Na4.67Eu0.67M′0.33(MoO4)4 · yH2O (y = 1, 1, 2, 2 for M′ = Si, Ge, Sn, Pb, respectively) is lower than that of their corresponding anhydrous phosphors. This may be explained in terms of the vibrational frequencies and the low valent state of the chemical bonds. © 1990.