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

Irina Adell,Rosa Maria Solé,Francesc Díaz,Maria Cinta Pujol,Nadège Ollier,Magdalena Aguiló,Matthieu Lancry

doi:10.1038/s41598-020-63556-w

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, Pr3+-doped KGd(PO3)4 bulk single crystals with monoclinic structure (space group: P21) 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 Pr3+ level of doping and temperature is studied. Differential thermal analysis reveals that KGd0.942Pr0.058(PO3)4 is stable until 1140 K. The 5d3, 5d2 and 5d1 levels of Pr3+ with respect to the 3H4 ground state are centred at 166, 196 and 218 nm, respectively, in this host. The luminescence of KGd0.990Pr0.010(PO3)4, by exciting these 5d levels, shows intense emissions centred at 256 and 265 nm from the 5d1 to 3F3,4 and 1G4 levels of Pr3+ with a short decay time of 6 ns. The 6P3/2,5/2,7/2 → 8S7/2 transitions of Gd3+ appear after exciting the 5d levels of Pr3+ and the 4 f levels of Gd3+, showing an energy transfer between Pr3+ and Gd3+.

Highlights

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]
In positron emission tomography (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]
An intense, broad emission band located around 256–265 nm was observed in all grown crystals, corresponding to the 5d1 → 3F3,4 and 5d1 → 1G4 electronic transitions of Pr3+

Summary

Introduction

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]. 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]. Ce3+ and Pr3+ 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]. Lu2SiO5 (LSO) doped with Pr3+ has been studied and the photoluminescence of the 5d → 4 f electronic transition at 273 nm shows a fast decay time of 6–7 ns. Ce3+- and Pr3+-doped NaLa(PO3)[4] were studied under VUV-UV excitation by Kang et al.[14], showing decay times for the 5d → 4 f transitions of Ce3+ of 22.7–23.8 ns and of Pr3+ of 9.9–12.9 ns

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