Synthesis and photoluminescence properties of Mn2+ doped Ca1-xSrxCN2 phosphors prepared by a carbon nitride based route

Mn2+ doped Ca1-xSrxCN2 phosphors were synthesized by a solid-state reaction in only 1 ​h under NH3 atmosphere at 700 ​°C from doped calcium carbonate and carbon nitride as precursors. The samples were characterized by powder X-ray diffraction, scanning electron microscopy and their diffuse reflectance and luminescence properties were investigated in order to evaluate the potential of such systems as red phosphors. All pure and well-crystallized Mn2+ doped samples exhibit broad red emission around 680 ​nm when excited at 270 ​nm at room temperature corresponding to the 4T1g(4G) → 6A1g(6S) transition. Maximum emission in CaCN2: Mn is obtained for Mn2+ content of 4 %mol and is stable up to 343 ​K and then shows a 20% decrease at 393 ​K. Finally, the progressive substitution of Sr2+ for Ca2+ evidences a solid solution domain between CaCN2 and β-SrCN2 with continuous increase of the crystal lattice dimensions. However, such substitution has no impact on the wavelength emission but leads to a decrease of the luminescence efficiency of the phosphor.