Effect of Bi_2O_3 doping on persistent luminescence of MgGeO_3:Mn^2+ phosphor

Abstract

The photoluminescence, persistent luminescence and thermoluminescence properties of Mg(0.998-x)Mn0.002BixGeO3 (x = 0, 0.001, 0.005, 0.01, 0.02) were investigated. A Mn-Bi co-doped sample with x = 0.005 showed the most intense red persistent luminescence due to the Mn2+:4T2→6A1 transition peaked at 680 nm. The persistent luminescence intensity of the sample with x = 0.005 was 30 times higher than that of the Mn singly doped sample (x = 0). All Mn-Bi co-doped samples showed an additional glow peak at approximately 320 K. From the continuous decrease of Bi3+ luminescence intensity in storage process by UV light, it was suggested that Bi itself functions as an electron-trapping center. We proposed an energy level diagram which explains red persistent mechanism in MgGeO3:Mn-Bi.