Single crystal growth, optical absorption and luminescence properties under VUV-UV synchrotron excitation of type III Ce³⁺:KGd(PO₃)₄, a promising scintillator material

Scintillator materials have gained great interest for many applications, among which the medical applications stand out. Nowadays, the research is focused on finding new scintillator materials with properties that suit the needs of each application. In particular, for medical diagnosis a fast and intense response under high-energy radiation excitation is of great importance. Here, type III Ce³⁺-doped KGd(PO₃)₄ single crystals with high crystalline quality are grown and optically characterized as a new promising scintillator material. The 4f → 5d electronic transitions of Ce³⁺ are identified by optical absorption. The optical absorption cross section of Ce³⁺ for the electronic transition from the ²F_5/2 to the 5d₁ level is 370 × 10⁻²⁰ cm². The luminescence of KGd_0.996Ce_0.004(PO₃)₄ crystal by exciting the 5d levels of Ce³⁺ with VUV-UV synchrotron radiation shows down-shifting properties with strong emissions at 322 and 342 nm from the 5d₁ to ²F_5/2 and ²F_7/2 levels of Ce³⁺ with a short decay time of ~16 ns, which is very suitable for scintillator applications. Moreover, these intense emissions are also observed when Gd³⁺ is excited since an energy transfer from Gd³⁺ to Ce³⁺ exists.