In this review, the major achievements and research and development (R&D) trends from the last decade in the field of single crystal scintillator materials are described. Two material families are included, namely, those of halide and oxide compounds. In most cases, the host crystals are doped with Ce3+, Pr3+ or Eu2+ rare earth ions. Their spin- and parity-allowed 5d–4f transitions enable a rapid scintillation response, on the order of tens to hundreds of nanoseconds. Technological recipes, extended characterization by means of optical and magnetic spectroscopies, and theoretical studies are described. The latter provide further support to experimental results and provide a better understanding of the host electronic band structure, energy levels of specific defects, and the emission centers themselves. Applications in medical imaging and dosimetry, security measures, high-energy physics and the high-tech industry, in which X(γ)-rays or particle beams are used and monitored, are recognized as the main driving factor for R&D activities in this field.

Recent R&D Trends in Inorganic Single-Crystal Scintillator Materials for Radiation Detection

Radiation detection, using materials to convert high-energy photons to low-energy photons (X-ray imaging) or electrical charges (X-ray detector), has become essential for a wide range of applicatio

Metal Halide Perovskites for X-ray Imaging Scintillators and Detectors

Abstract The discovery of inorganic phosphors that can be excited by GaN light emitting diodes in the wavelength range 380–460 nm is essential for improving the efficiency and light quality of solid state lighting devices. Garnets doped with Ce 3+ are of particular interest for this application. We have studied the luminescence of Ce 3+ in garnet phosphors and established a relationship between the excitation/emission wavelengths and the deviation from cubic symmetry around the rare-earth ion. Data are presented for both known yttrium aluminum and yttrium gallium garnet systems, as well as newly synthesized inverse garnets of the general formula Mg 3 Y 2− y Gd y Ge 3− z Si z O 12 :Ce (0 ⩽  y  ⩽ 2, z  = 0, 1).

http://ma.ecsdl.org/content/MA2007-02/33/1520.full.pdf

Structure-Property Correlations in Ce-Doped Garnet Phosphors for Use in Solid State Lighting

Transparent ceramics have various potential applications such as infrared (IR) windows/domes, lamp envelopes, opto-electric components/devices, composite armors, and screens for smartphones and they can be used as host materials for solid-state lasers. Transparent ceramics were initially developed to replace single crystals because of their simple processing route, variability in composition, high yield productivity, and shape control, among other factors. Optical transparency is one of the most important properties of transparent ceramics. In order to achieve transparency, ceramics must have highly symmetric crystal structures; therefore, the majority of the transparent ceramics have cubic structures, while tetragonal and hexagonal structures have also been reported in the open literature. Moreover, the optical transparency of ceramics is determined by their purity and density; the production of high-purity ceramics requires high-purity starting materials, and the production of high-density ceramics requires sophisticated sintering techniques and optimized sintering aids. Furthermore, specific mechanical properties are required for some applications, such as window materials and composite armor. This review aims to summarize recent progress in the fabrication and application of various transparent ceramics.

Materials development and potential applications of transparent ceramics: A review

Lu2(1-x)Y2xSiO5:Ce (10 at% Y) single crystals co-doped with Ca2+ and Mg2+ were prepared by the Czochralski technique. It is shown that co-doping leads to significant improvements of the scintillation performances. Afterglow following X-ray excitation is reduced down to 200 ppm after 20 ms and light yield is increased from 28,000 ph/MeV up to 34,000 ph/MeV under 137Cs-662 keV excitation. X-ray Absorption Near Edge Spectroscopy (XANES) was used to demonstrate that a significant part of the Ce ions are stabilized in the Ce4+ oxidation state in co-doped crystals. A new scintillation mechanism involving Ce4+ is proposed.

Evidence and Consequences of Ce $^{4+}$ in LYSO:Ce,Ca and LYSO:Ce,Mg Single Crystals for Medical Imaging Applications

In this paper, we investigate the temperature dependence of luminescence characteristics of highly efficient cerium-doped scintillator, lutetium-yttrium orthosilicate Lu2(1−x)Y2xSiO5:Ce3+. The photoluminescence excitation and emission spectra have been measured in a broad temperature range. The temperature dependence of the Ce1 and Ce2 decay times shows the onset of decay time decrease at about 300 K. This observation demonstrates that unlike so far reported, the Ce2 center is not substantially quenched until room temperature. The 5d1 excited-state ionization of both Ce1 and Ce2 centers is studied by purely optical methods.

Temperature dependence of luminescence characteristics of Lu2(1−x)Y2xSiO5:Ce3+ scintillator grown by the Czochralski method

Ce3+-doped oxide glass with high Gd2O3 (30 mol%) concentration was prepared as a scintillating glass under CO reducing atmosphere. A dominant emission band of the Ce3+ 5d  4f transition peaking around 400 nm was observed in the photo- and radioluminescence (PL, RL) spectra. PL decay was governed by a few tens of nanoseconds decay time. The integral scintillation efficiency of about 30% of the Bi4Ge3O12 scintillator was observed as well. It exhibits a light yield of about 910 photons/MeV with an energy resolution of 18.3% (FWHM) in the pulse height spectrum of 662 keV γ-rays from a 137Cs source.

Luminescence and scintillation of Ce3+-doped oxide glass with high Gd2O3 concentration

Zero‐Dimensional Cs 3 Cu 2 I 5 Perovskite Single Crystal as Sensitive X‐Ray and γ‐Ray Scintillator

Ultrabright and Highly Efficient All-Inorganic Zero-Dimensional Perovskite Scintillators

0.5, 1.0, and 5.0 at. % Pr3+ doped Lu3Al5O12 (Pr:LuAG) optical ceramics are fabricated and compared with Bi4Ge3O12 (BGO) and Pr:LuAG single crystals as for their optical, luminescence and scintillation properties. Radio-luminescence intensity of the fast UV emission based on 5d1→4f Pr3+ transition reaches up to 20 times of that of BGO single crystal reference scintillator. Photoelectron yield of the best performing 0.5 at. % Pr:LuAG ceramic sample is about 1002 phels/MeV, about 30% lower than that of BGO reference sample and about 65% lower than that of Pr:LuAG single crystal. The trapping phenomena at grain boundaries and/or structural defects are proposed as the main cause of degradation of the scintillation response of the Pr:LuAG optical ceramics.

Romana Kucerkova

Papers

Temperature dependence of luminescence characteristics of Lu2(1−x)Y2xSiO5:Ce3+ scintillator grown by the Czochralski method

Luminescence and scintillation of Ce3+-doped oxide glass with high Gd2O3 concentration

Zero‐Dimensional Cs 3 Cu 2 I 5 Perovskite Single Crystal as Sensitive X‐Ray and γ‐Ray Scintillator

Ultrabright and Highly Efficient All-Inorganic Zero-Dimensional Perovskite Scintillators

Microstructure, optical, and scintillation characteristics of Pr3+ doped Lu3Al5O12 optical ceramics