Photoluminescence behavior of the Sm3+ and Tb3+ ions doped into the Gd2(WO4)3 matrix prepared by the Pechini and ceramic methods

the gd2(wo4)3:re3+ compounds (where re3+ = sm and tb) were prepared by the pechini and ceramic methods and characterized by x-ray diffraction and infrared spectroscopy. these rare earth materials present high orange (sm3+-compound) and green (tb3+-compound) luminescence intensity under uv radiation. the excitation spectra of these compounds presented broad bands arising from ligand-to-metal charge transfer (o？w and o？re3+) and narrow bands from 4f-intraconfigurational transitions. the excitation spectra of tb3+ system also exhibit broad bands attributed to the interconfigurational transition (4f-5d). the emission spectra exhibited the 4g5/2？6hj (j = 5/2, 7/2, 9/2 and 11/2) and 5d4？ 7fj (j = 0-6) transitions (direct excitation), for the systems doped with sm3+ and tb3+, respectively, while a broad band assigned to the lmct (o？w) is observed when the excitation is monitored on the o？w lmct state around 270 nm. the experimental intensity parameters hsm and heu present similar behaviors, suggesting that the sm3+ ion is in a highly polarizable chemical environment with similar covalent character of the metal-donor atom interaction to the tungstate doped europium system. the cross-relaxation process from the 5d3 to the 5d4 levels of the gd2(wo4)3:tb3+ system has been also reported.