A novel white-light-emitting phosphor, 12CaO·7Al2O3:Ce3+, Dy3+with H− encaging, was prepared by the solid-state reaction in H2 atmosphere. Upon excitation at 362 nm, the phosphor shows intense white-light emission that combines the blue and yellow emissions at 476 and 576 nm, assigned to the 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 transitions of Dy3+, respectively. A weak broad blue emission centered at 430 nm is also observed and attributed to the 5d–4f transitions of Ce3+. The photoluminescence intensity of Dy3+ increases greatly with increasing Ce3+concentration, indicating that the effective energy transfer occurred from Ce3+ to Dy3+ in the phosphor. In particular, the phosphor can be converted to a persistent semiconductor upon ultraviolet irradiation due to the electrons released from the encaged H− ions, and the electrical conductivity is measured to be 10−2 S cm−1. The conductive phosphor exhibits excellent white-light emission (CIE coordinate of (0.324, 0.323)) under low-voltage (5 kV) electron beam excitation, suggesting that the phosphor is a potential candidate for applications in field emission displays.