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

Abstract

We have studied the luminescence property of CaMoO₄:Eu³⁺. The emission peaks at 590 (⁵D₀→⁷F₁) and 613 nm (⁵D₀→⁷F₂) for Eu³⁺ 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 Eu³⁺ in EuO₈ polyhedron or parity mixing. Luminescence intensity increases significantly with co-doping of Gd³⁺. This is ascribed to energy transfer from Mo–O/Gd³⁺ to Eu³⁺. 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% Gd³⁺ co-doped CaMoO₄:Eu³⁺ under 277 nm (UV excitation) are 21 and 80%, respectively.