Upconversion luminescence of KGd(MoO 4) 2:Er 3+,Yb 3+ powder prepared by Pechini method

Abstract

Er 3+ doped potassium gadolinium molybdate (KGM) phosphor with sensitizer Yb 3+ ion was synthesized by the Pechini method using citric acid and ethylene glycol. The crystallization processes of the phosphor precursors were characterized by X-ray diffraction (XRD) and thermogravimetry-differential scanning calorimetry (TG-DSC), which indicated that ultrafine uniform crystallites of KGM:Er,Yb were obtained by sintering the precursors at above 650 °C for 5 h. Upconversion luminescence (UL) spectra of the samples were studied by a 976 nm semiconductor laser diode (LD) excitation. The UL spectra exhibited the green and red emission bands that were attributed to the 2H 11/2, 4S 3/2→ 4I 15/2 and 4F 9/2→ 4I 15/2 transitions of Er 3+, respectively. The possible UL mechanisms of Er 3+ were explained by means of an energy level diagram. The maximum luminescent intensity was achieved when the concentration of Er 3+, Yb 3+ arrived at 1 mol.% and 20 mol.%, respectively.