Temperature variable luminescence and color tuning of Eu2+/Mn2+-codoped strontium magnesium phosphates as promising red-emitting phosphors for light emitting diodes

Eu2+ and Mn2+ codoped violet-/red-emitting strontium magnesium phosphates, SrMgP2O7, SrMg2P2O8 and Sr2Mg3P4O15, were prepared and their emission properties, especially for color tuning with temperature variable luminescence, were investigated. Simply by changing the host composition of the SrO-MgO-P2O5 ternary system, we can control the Eu2+-sensitized Mn2+ emission efficiency as well as the thermal quenching of incorporated activators. We can realize that the overall luminescence behavior is induced by the Mn2+ center positioned at different coordination states with intermixed Sr2+/Mg2+ sites in various hosts, which resulted in widely tunable colors from violet-red through orange-red to pure red. Finally, bright and stable reddish color illuminated light emitting diodes (LEDs) can be obtained by combining the proposed phosphates with ultraviolet LEDs, demonstrating the potential red-emitting phosphors for ultraviolet-pumped phosphor converted white-LEDs.