Photoluminescence and cathodoluminescence properties of green-red emitting ZnGd4Si3O13: Tb3+, Mn2+ phosphors

The photoluminescence and cathodoluminescence properties of new silicate oxyapatite phosphors ZnGd4Si3O13: Tb3+, Mn2+ were investigated in this study. The Rietveld refinement indicated that the prepared phosphors exhibited a hexagonal structure with space group P6(3)/m (no. 176). Under UV excitation, ZnGd4Si3O13: Mn2+ phosphors presented a red emission band due to the T-1((4)G)-(6)A(1)(S-6) transition of Mn2+ ions, while ZnGd4Si3O13: Tb3+ showed several emission lines at 490, 544, 585 and 621 nm attributed to the D-5(4)-> F-7(J) (J = 6, 5, 4, 3) transitions of Tb3+ ions. The co-doping of Tb3+ ions into ZnGd4Si3O13: Mn2+ resulted in a 100% enhancement of the photoluminescence intensity for Mn2+ ions through a dipole-dipole energy transfer mechanism. On the other hand, the energy transfer process from the sensitizers (Tb3+) to the activators (Mn2+) led to a decrease in Tb3+ emission as co-doping Mn2+ ions into ZnGd4Si3O13: Tb3+. Increasing the concentration of Mn2+ ions from x = 0.02 to x = 0.08 for Zn2-xMnxGd3TbSi3O13 efficiently enhanced the energy transfer efficiency from 90 to 98%. Under the electron-beam excitation, the emission spectra of phosphors were similar to those observed under UV excitation. However, a deviation of CIE coordinates was found under the electron-beam excitation due to the relatively unapparent energy transfer between Tb3+ and Mn2+ ions. The present results suggested a new series of color-tunable phosphors which can be used for both photoluminescence and cathodoluminescence applications.