Red phosphorescence properties on Mn ions doped MgO-GeO 2 compounds, Mg 4 GeO 6 , Mg 2 GeO 4 , and MgGeO 3 , were investigated. The red phosphorescence was observed in MgGeO 3 :Mn 2þ . The red phosphorescence intensity of MgGeO 3 :Mn 2þ increased with adding the MgF 2 and Yb 2 O 3 . The red phosphorescence duration time of sample with a batch composition of 44 mol%-MgO, 6 mol%-MgF 2 , 50 mol%-GeO 2 , 0.1 mol%-MnO, and 0.05 mol%-Yb 2 O 3 is approximately 30 min. The mechanism of red phosphorescence in MgGeO 3 :Mn 2þ is discussed in terms of the relationship between valency state of manganese ions and point defects in matrix compound. q

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