Effect of doping mode on the photoluminescence property of CaS:Eu phosphor

Eu-doped CaS phosphors were prepared from sulfurization of CaCO₃ in H₂S gas without flux. The doping of Eu activator was conducted in two different modes: synchronous doping during sulfurization of CaCO ₃ and subsequent doping by vacuumly calcinning pure CaS and Eu ₂O₃. Comparison of the as-prepared samples indicated that subsequent doping led to larger optimum Eu concentration and lower red emission intensity than synchronous doping. The different luminescence properties are ascribed to the different activator distributions in CaS host induced by different doping modes, and the uniform distribution resulted from synchronous doping is beneficial to the luminescence of the phosphor.