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 2F5/2 to the 5d1 level is 370 × 10−20 cm2. The luminescence of KGd0.996Ce0.004(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 2F5/2 and 2F7/2 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.

Scintillator materials are widely used for a variety of applications such as high energy physics, astrophysics and medical imaging. Since the ideal scintillator does not exist, the search for scintillators with suitable properties for each application is of great interest. Here, pr 3+-doped KGd(po 3) 4 bulk single crystals with monoclinic structure (space group: P2 1) are grown from high temperature solutions and their structural, thermal and optical properties are studied as possible candidates for scintillation material. the change in the unit cell parameters as a function of the pr 3+ level of doping and temperature is studied. Differential thermal analysis reveals that KGd 0.942 pr 0.058 (po 3) 4 is stable until 1140 K. The 5d 3 , 5d 2 and 5d 1 levels of pr 3+ with respect to the 3 H 4 ground state are centred at 166, 196 and 218 nm, respectively, in this host. The luminescence of KGd 0.990 pr 0.010 (po 3) 4 , by exciting these 5d levels, shows intense emissions centred at 256 and 265 nm from the 5d 1 to 3 f 3,4 and 1 G 4 levels of pr 3+ with a short decay time of 6 ns. The 6 p 3/2,5/2,7/2 → 8 S 7/2 transitions of Gd 3+ appear after exciting the 5d levels of pr 3+ and the 4 f levels of Gd 3+ , showing an energy transfer between pr 3+ and Gd 3+. Inorganic scintillation materials are widely used in a variety of applications in the field of particles and ionizing radiation detection such us medical imaging, dosimetry, nuclear physics and astrophysics 1. Current research is focused on the search for new materials with improved scintillation properties 2. Ray imaging techniques for medical imaging include planar X-ray photography, computed tomography (CT) and positron emission tomography (PET). In the first of these, the number of UV-vis photons emitted by the scintillator material per energy unit of the incoming X-ray photons (light yield) should be high in order to decrease the X-ray dose to the patient. In CT, the stability of the light output should be as high as possible to achieve reliable images and therefore better diagnostics. In PET, a fast decay time of the UV-vis photons emitted by the scintillator is required for any improvement in spatial resolution and sensitivity, since this technique is based on a precise temporal measurement of two simultaneously emitted gamma photons at nearly 180° during a positron-electron annihilation process 3,4. Ce 3+ and Pr 3+ have been used as doping ions in the vast majority of the new single crystal scintillators reported over the last approximately 20 years because of the fast decay time of the 5d → 4 f radiative transitions (usually from 10 to 60 ns), together with the high quantum efficiency of these transitions at room temperature 2. The scintillation properties of Ce 3+-and Pr 3+-doped garnets have been optimized by the growth of multicomponent doped hosts like (Gd,Lu) 3 Ga 3 Al 2 O 12 5-8. As regards aluminium perovskite crystals, fast lifetimes corresponding to the 5d → 4 f transitions of Ce 3+ and Pr 3+ ions doped in YAlO 3 host have been obtained at around 18 a...

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Scintillator materials are used as detectors in the ray imaging techniques for medical diagnosis. Because the ideal medical scintillator material does not exist, many efforts are being made to find new materials that satisfy a greater number of properties. Here, the synthesis conditions of Pr:KGd(PO 3 ) 4 nanocrystals by the modified Pechini method are optimized to obtain a single crystalline phase of those that form the polymorphism of KGd(PO 3 ) 4 . The interest lies in the type III phase because less quenching by Pr 3+ concentration is expected. By performing transmittance measurements and because of the wide transparency window of the type III KGd(PO 3 ) 4 host, the 3 H 4 → 5d 1 absorption transition of Pr 3+ has been observed in the vacuum ultraviolet spectral range. After creating electron–hole pairs in the host due to the excitation of the material by X-ray radiation, the bands corresponding to the 5d 1 → 3 H 4 , 3 H 5 , 3 H 6 and 5d 1 → 3 F 3 , 3 F 4 , 1 G 4 transitions of Pr 3+ have been observed in the near-visible spectral range, being these 5d → 4f transitions interesting for scintillation applications. Therefore, the type III Pr:KGd(PO 3 ) 4 nanocrystals allow the conversion from high-energy radiation to visible or near-visible light.