BaF₂, the fastest known scintillator, is a very attractive material for γ-ray detection and light charged particles.The BaF₂ doped with rare earth ions, such as the Ce³⁺ ion, can suppress the slow components. Ce:BaF₂, a reasonably fast, efficient and rugged scintillator characterized by a reasonable stopping power, good matching refraction index and availability of large size crystals, was first proposed in 1977 as a substitute for BaF₂, which it is also the most efficient of all the rare-earth-doped alkaline earth fluorides.

Ce:BaF₂ Scintillator Crystal— A reasonably fast and rugged scintillator

BaF₂ has a decay time of less than 1 ns, which makes it unique among the high-Z scintillators and consequently very attractive for many applications where good timing is important.  BaF₂ has a low refractive index of about 1.478 at a wavelength of 500 nm and can be relatively easily matched with a proper polymeric matrix. Moreover, BaF₂’s conversion of light for ionising radiation is quite linear with energy. However, the integrated intensity of the fast component is low and the emission spectrum of BaF₂ contains an exciton band with undesirably long decay time. This problem can be solved by the introduction of an activator, which transforms the exciton emission into the faster activator luminescence. Trivalent cerium has been became a natural choice for the activator, because the Ce³⁺ ion has a fairly short decay time. Ce:BaF₂ scintillator is a well-known, reasonably fast and efficient scintillator characterized by a decent stopping power and availability of large size crystals. Bulk single crystalline  Ce:BaF₂ have been used as traditional scintillators for gamma ray detection.