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In this article, we report on crystal growth, density functional theory (DFT) calculations, and scintillation properties of TlCaX $_{3} (X =$ Cl, Br, I). Crystals were grown by the vertical Bridgman technique in silica ampoules. Crystals of TlCaCl3, TlCaBr3, and TlCaI3 belong to the family of perovskites and have an orthorhombic crystal structure. All three compositions show bright emission under X-ray excitation peaking at 425, 470, and 545 nm, respectively. Light yield increases in the series Cl < Br < I [25 000–47 000 photons/MeV (ph/MeV)].

Present paper reports an approach to BaI2:Eu2+glass ceramic fabrication from a powder route. The structural, morphological, luminescent and paramagnetic properties of the materials synthesized this way have been investigated. X-ray diffraction analysis made evidence for the glass ceramics containing BaI2·2H2O and BaI2inclusions when 50wt.% of the starting iodide powder had been used in the synthesis process. According to scanning electron microscopy, only two samples demonstrated presence of ceramics particles inside: those with initial mix of 25 and 50wt.% of the BaI2:Eu2+. Photoluminescence spectra could be measured only in these samples. They were multicomponent as compared to the single band spectrum observed in the BaI2:Eu2+powder. Altogether this indicates europium distribution over several places with different environments in the materials. BaI2dissolution in the glass matrix is confirmed further by electron paramagnetic resonance measurements. They have shown that the Eu2+ions predominantly stay in the glass avoiding ceramic grains. Only negligibly small amount presumably occupies the ceramic part in the sample with the initial 50wt.% part of the BaI2powder. The Eu2+→Eu3+charge transformation under 442nm laser light irradiation has been observed in the glass ceramics as well.

We generated high-entropy (HE) compositions of rare-earth (RE) monoclinic aluminates using a combinatorial approach, grew crystals from the melt using the micropulling down method, and investigated phase formation, microstructure, and elemental segregation. All RE elements, except for Pmand Tm, were used to generate RE4Al2O9compounds of five RE elements taken in equimolar ratios. The distribution of HE formulations was demonstrated as a function of the average ionic radii (AIR). The compositions were grouped based on their AIR that is equal to those of RE ions in single-rare-earth compounds: Y4Al2O9(Y group), Tb4Al2O9(Tb group), Gd4Al2O9(Gd group), and Nd4Al2O9(Nd group). Single monoclinic phases and uniform microstructures were observed in the Y group. Dot-, line-, and core-like inclusions of the secondary REAlO3perovskite phase were found in crystals of the Tb group and the Gd group in scanning electron micrographs. The concentration of the secondary phase increased with the fraction of bigger RE elements, such as La, Ce, Pr, Nd, and Sm in the HE formulation, as confirmed by X-ray diffraction. Incongruent melt solidification was found for compounds of the Nd group. Our results demonstrated that the stability of the monoclinic phase decreased with the AIR value in the sequence of the Y group, Tb group, Gd group, and Nd group, similar to their single-rare-earth compounds. Minor random variations in cell parameters between the seed and tail sides were found in crystals from the Y group, Tb group, and Gd group, indicating no pronounced elemental segregation. Based on the ionic radii of RE elements and their fraction in the HE formulation, recommendations were given on how to minimize the secondary phase.

The glass‐ceramics (GC) of gadolinium aluminum gallium garnets with the expected composition of Gd3Al3Ga2O12:Ce and Gd3Al3Ga2O12:Ce,Be (GAGG:Ce and GAGG:Ce,Be, respectively) are fabricated by crystallization from the Gd2O3–Al2O3–Ga2O3–CeO2–SiO2–BeO (Gd:Ga:Al ratio is close to 3:2:3) glasses. The influence of Be2+co‐doping (including doping level) on the luminescent properties of the GAGG is demonstrated. In particular, Be co‐doping results in the suppression of the Ce3+‐related radioluminescence (RL) and as a consequence, the light yield is lowered as well. The conclusion is made that Be2+creates effective electron or hole trapping centers. The article is about the glass‐ceramics form of Gd3Al3Ga2O12:Ce and Gd3Al3Ga2O12:Ce,Be, gadolinium aluminum gallium garnets. Be2+co‐doping affects the luminescent properties of Ce3+in these materials by the suppression of light yield. Moreover, the decay time of the photoluminescence (PL) decreases upon beryllium content. These observations lead to the conclusion of the effective beryllium‐based charge trapping centers’ existence.