Single-Phased White-Emitting 12CaO·7Al2O3:Ce3+, Dy3+ Phosphors with Suitable Electrical Conductivity for Field Emission Displays

A novel white-light-emitting phosphor, 12CaO·7Al ₂O ₃:Ce ³⁺, Dy ³⁺with H ^- encaging, was prepared by the solid-state reaction in H ₂ 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 ⁴F _9/2 → ⁶H _15/2 and ⁴F _9/2 → ⁶H _13/2 transitions of Dy ³⁺, respectively. A weak broad blue emission centered at 430 nm is also observed and attributed to the 5d-4f transitions of Ce ³⁺. The photoluminescence intensity of Dy ³⁺ increases greatly with increasing Ce ³⁺ concentration, indicating that the effective energy transfer occurred from Ce ³⁺ to Dy ³⁺ 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.