In this study, the single-phase warm white-light phosphors were synthesized by the conventional solid-state reaction method. A phosphor composed of CaSnO3 with the additions of Ce3+ (0.5 wt%) and Mn4+ (0.3 wt%) shows the optimum emission intensity at a correlated color temperature of 3758 K when excited by a 266 nm laser. The luminescence of another CaSnO3phosphor with the additions of Ce3+ (0.5 wt%), Mn4+ (0.2 wt%), and Dy3+ (0.3 wt%) at a CCT of 3998 K is also studied by an excitation at 325 nm. In addition, the spectral overlap between the emission band of Ce3+ and the excitation band of Mn4+ supports the occurrence of the energy transfer from Ce3+ to Mn4+. The speculated energy transfer mechanism between Ce3+ and Mn4+ has been studied and demonstrated to be the exchanged interactions mechanism. Moreover, the concentration quenching was also observed, and the related critical distance of energy transfer evaluated by the concentration quenching methods is about 23.426 Å.
