Single-phased white-emitting 12CaO·7Al2O3:Ce3+, Dy3+ phosphors with suitable electrical conductivity for field emission displays

Abstract

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 ⁴F_9/2 → ⁶H_15/2 and ⁴F_9/2 → ⁶H_13/2 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.