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Recent research activity on Sm2+-doped compounds has significantly increased the amount of available data on 4f55d → 4f6 decay times. This enabled the systematic comparison of spectroscopic and time resolved luminescence data to theoretical models describing the interplay between the 4f55d and 4f6[5D0] excited states on the observed decay time. A Boltzmann distribution between the population of the excited states is assumed, introducing a dependence of the observed 4f55d → 4f6 decay time on the energy gap between the 4f55d and 4f6[5D0] levels and temperature. The model is used to interpret the origin of the large variation in reported 4f55d → 4f6 decay times through literature, and links their temperature dependence to applications such as luminescence thermometry and near-infrared scintillation. The model is further applied to the analogous situation of close lying 4fn-15d and 4fn states in Eu2+ (6P7/2) and Pr3+ (1S0)., RST/Luminescence Materials

Components manufactured with Metal Laser Powder Bed Fusion (PBF-LB/M) are built in a layerwise fashion. The PBF-LB/M build orientation affects grain morphology and orientation. Depending on the build orientation, microstructures from equiaxed to textured grains can develop. In the case of a textured microstructure, a clear anisotropy of the mechanical properties affecting short- and long-term mechanical properties can be observed, which must be considered in the component design. Within the scope of this study, the IN738LC tensile and creep properties of PBF-LB/M samples manufactured in 0° (perpendicular to build direction), 45° and 90° (parallel to build direction) build orientations were investigated. While the hot tensile results (at 850 °C) are as expected, where the tensile properties of the 45° build orientation lay between those of 0° and 90°, the creep results (performed at 850 °C and 200 MPa) of the 45° build orientation show the least time to rupture. This study discusses the microstructural reasoning behind the peculiar creep behavior of 45° oriented IN738LC samples and correlates the results to heat-treated microstructures and the solidification conditions of the PBF-LB/M process itself.

Currently only Eu2+-based scintillators have approached the light yield needed to improve the 2% energy resolution at 662 keV of LaBr3:Ce3+,Sr2+. Their major limitation, however, is the significant self-absorption due to Eu2+. CsCu2I3 is an interesting new small band gap scintillator. It is nonhygroscopic and nontoxic, melts congruently, and has an extremely low afterglow, a density of 5.01 g/cm3, and an effective atomic number of 50.6. It shows self-trapped exciton emission at room temperature. The large Stokes shift of this emission ensures that this material is not sensitive to self-absorption, tackling one of the major problems of Eu2+-based scintillators. An avalanche photo diode, whose optimal detection efficiency matches the 570 nm mean emission wavelength of CsCu2I3, was used to measure pulse height spectra. From the latter, a light yield of 36 000 photons/MeV and energy resolution of 4.82% were obtained. The scintillation proportionality of CsCu2I3 was found to be on par with that of SrI2:Eu2+. Based on temperature-dependent emission and decay measurements, it was demonstrated that CsCu2I3 emission is already about 50% quenched at room temperature. Using temperature-dependent pulse height measurements, it is shown that the light yield can be increased up to 60 000 photons/MeV by cooling to 200 K, experimentally demonstrating the scintillation potential of CsCu2I3., RST/Luminescence Materials

LaBr3:Ce3+ is a compound with excellent scintillation properties, but its ultraviolet emission does not match well with the detection efficiency curves of silicon based photodetectors. In this work, Sm2+ is studied as an activator for LaBr3 as its near-infrared emission can be detected with close to 100% efficiency by such photodetectors. LaBr3:Sm2+ single crystals were grown with and without co-doping of Ce3+ or Pr3+. The samples were studied by means of X-ray excited and photoluminescence spectroscopy at temperatures between 10 K and 300 K. Their spectroscopic properties are compared to LaBr3:Ce3+ and LaBr3:Eu2+. The effect of using Ce3+ or Pr3+ as scintillation sensitiser for Sm2+ is assessed. It is found that energy transfer from host to Sm2+ greatly improves upon Ce3+ co-doping, but the quenching temperature of the Sm2+ emission decreases. The quenching mechanism of both the Ce3+ and Sm2+ emission in LaBr3 is elaborated on. Furthermore, the effect of charge compensating defects on the light yield and spectroscopic properties is discussed., RST/Luminescence Materials

The benefits of doping Cs4EuBr6 and Cs4EuI6 with Sm2+ are studied for near-infrared scintillator applications. It is shown that undoped Cs4EuI6 suffers from a high probability of self-absorption, which is almost completely absent in Cs4EuI6:2% Sm. Sm2+ doping is also used to gain insight in the migration rate of Eu2+ excitations in Cs4EuBr6 and Cs4EuI6, which shows that concentration quenching is weak, but still significant in the undoped compounds. Both self-absorption and concentration quenching are linked to the spectral overlap of the Eu2+ excitation and emission spectra which were studied between 10 K and 300 K. The scintillation characteristics of Cs4EuI6:2% Sm is compared to that of the undoped samples. An improvement of energy resolution from 11% to 7.5% is found upon doping Cs4EuI6 with 2% Sm and the scintillation decay time shortens from 4.8 s to 3.5 s in samples of around 3 mm in size., RST/Luminescence Materials