Single crystal growth, optical absorption and luminescence properties under VUV-UV synchrotron excitation of type III Pr3+:KGd(PO3)4

Abstract

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...

Structural and Optical Properties of High Entropy (La,Lu,Y,Gd,Ce)AlO3 Perovskite Thin Films

“…Our observation is consistent with the signature peak seen in the UV–Vis spectra above and reported in the literature. [ 17,21,42,64 ] As can be seen from Figure 5b, the intensity of the REHEPO/LAO heterostructure is much stronger than that of the substrate alone. This indicates that the luminescence comes mainly from the REHEPO film with little or negligible contribution from the substrate.…”

“…Figure 5b shows a low intensity longer wavelength emission peak of 616.5 nm that corresponds to the 6 G J → 6 P J transition in Gd 3+ and is likely the resulting emission of a two‐photon process. [ 64,65 ] Luminescence from this transition in Gd 3+ may be due to the combination of two photons with wavelengths of 289 nm that create an exciton from the ground state, 8 S 7/2 , reaching above or within 6 G J energy levels before recombining and emitting the observed 616.5 nm peak. The characteristic 6 P J → 8 S 7/2 transition within Gd 3+ can be considered energy loss or inefficiencies with respect to the most desirable 405 nm emission.…”