Mn2+ concentration manipulated red emission in BaMg2 Si2 O7: Eu2+, Mn2+

The luminescent properties of concentration dependence are reported in BaMg2 Si2 O7: Eu2+, Mn2+ red phosphor. It is observed that the broad red emission of Mn2+ consists of two bands, located at 620 and 675 nm, respectively, which are attributed to two different Mn2+ centers [Mn2+ (I) and Mn2+ (II)] substituting for two nonidentical Mg2+ sites [Mg2+ (I) and Mg2+ (II)] in the host. It is also found that the relative emission intensity of the Mn2+ (II) to the Mn2+ (I) increases with increasing Mn2+ concentration, leading to a red-shift of the overall emission. A detail analysis on the energy transfer from Eu2+ to the two Mn2+ centers is presented, which indicates that the number ratio of Mn2+ (II) to Mn2+ (I) increases with increasing Mn2+ concentration. This result is interpreted by the preferential formation of Mn2+ (I) substituting for Mg2+ (I) site. Based on energy transfer, the emission intensity ratios of Mn2+ (I) to Eu2+ and Mn2+ (II) to Eu2+, which is Mn2+ concentration dependent, are calculated using related fluorescence lifetimes. The calculated results are in good agreement with that obtained experimentally in the emission spectra.