A series of Ce ³⁺ doped α -Sr _{2-2 x} Ce _x Na _x P ₂ O ₇ phosphor compounds has been prepared using a high-temperature solid-state reaction technique. The luminescence properties under vacuum ultraviolet-UV and x-ray excitation were studied. Luminescence spectra reveal three UV-emitting peaks at about 310, 330, and 350 nm from which we conclude that Ce ³⁺ occupies two distinct sites in α -Sr ₂ P ₂ O ₇ . The influences of the doping concentration, the temperature, and the excitation wavelength on the luminescence of Ce ³⁺ at the Ce(I) and Ce(II) sites together with the decay characteristics are discussed. The light yield under x-ray excitation is found to be around 10 000 photons/MeV.