Enhanced photoluminescence in CaMoO4:Eu3+ by Gd3+ co-doping

We have studied the luminescence property of CaMoO4:Eu(3+). The emission peaks at 590 ((5)D0→(7)F1) and 613 nm ((5)D0→(7)F2) for Eu(3+) are observed after excitation at 266 nm (i.e. Mo-O charge transfer band). The peak intensity of the latter dominates over the former indicating an asymmetric environment of Eu(3+) in EuO8 polyhedron or parity mixing. Luminescence intensity increases significantly with co-doping of Gd(3+). This is ascribed to energy transfer from Mo-O/Gd(3+) to Eu(3+). Luminescence intensity increases with annealing up to 900 °C due to the extent of decrease of non-radiative rates. Very high asymmetric values (A21) of 12-16 are found indicating a red emitter. As-prepared samples are dispersible in polar solvents like water, ethanol, methanol, dimethyl sulfoxide (DMSO) and ethylene glycol (EG); and among them, optimum luminescence is found in methanol. Polymer film shows red emission. The quantum yields of as-prepared 2 and 10 at% Gd(3+) co-doped CaMoO4:Eu(3+) under 277 nm (UV excitation) are 21 and 80%, respectively.