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Commercial Bi4Ge3O12 (BGO) monocrystal scintillator is relatively complicated to produce and too expensive. Therefore, it is desired to look for alternative scintillating materials with simple process, low consumption, large size, and high efficiency. Here, glass‐ceramics (GC) with high volume fraction of crystal phase and high density by increasing the proportion of heavy metal fluorides in the composition were designed. And bulk Tb3+‐doped transparent BaGdF5 glass‐ceramics with 23.3% crystal volume ratio and density of 4.65 g/cm3 have been prepared. The structural, optical, and luminescent properties of precursor glass and GC were systematically explored through series of characterization techniques including X‐ray diffraction (XRD), transmittance spectra, transmission electron microscope (TEM), photoluminescence (PL) spectra, and X‐ray excited luminescence (XEL). After heat treatment, both PL emission and XEL intensity of GC are enhanced because of the movement of Tb3+ ions from the amorphous glass matrix into BaGdF5 nanocrystals, which possess lower phonon energy and better crystal field. The luminescent quantum efficiency of GC reaches 30.7% and the XEL intensity of GC is around 140% of that of the commercial BGO scintillating crystal. Our results demonstrate that BaGdF5:Tb3+ GC may act as efficient scintillator for X‐ray detection. [ABSTRACT FROM AUTHOR]

Mixed‐valence Eu‐doped transparent oxyfluoride glass‐ceramics containing cubic LaF3 nanocrystals were fabricated by traditional melt‐quenching technique and consequent annealing processes. Their structural and luminescent properties were systemically investigated by X‐ray diffraction (XRD), transmission electron microscopy, absorption, excitation, emission spectra, and fluorescence lifetime measurements. Analyses of XRD patterns prove that the new precipitated nanocrystals disperse in glass‐ceramics crystallize in cubic LaF3. The spectroscopic investigations show that Eu2+ ions have been incorporated into the LaF3 nanocrystals preferentially, while Eu3+ ions still remain in the glass phase after crystallization. Based on the spectral results, a new parameter Rchange=RGC-RPG/RGC was defined to describe the changes of the environments of Eu3+ before and after crystallization more straightforwardly and more sensitively, where RPG and RGC represent the integrated intensity radio of 5D0 → 7F2 to 5D0 → 7F1 emissions of Eu3+ in PG and GC samples, respectively. Our investigation will not only enrich the understanding of fluoride nanocrystals‐based oxyfluoride glass‐ceramics, but also the distribution and luminescence behaviors of Eu3+ ions in them. [ABSTRACT FROM AUTHOR]

An ever increasing demand for white light‐emitting diodes (W‐LEDs) results in the gradual growth of research on functionalized luminescent glasses. In this paper, single‐composition tunable white‐emitting Eu2+‐Tb3+‐Eu3+ tri‐activated glasses were synthesized by melt quenching method without additional reducing atmosphere. The coexistence of Eu2+ and Eu3+ was confirmed by ultraviolet‐visible transmission spectra, photoluminescent spectra, fluorescence decay curves, and X‐ray photoelectron spectroscopy. Tb3+ can act as bridge to connect Eu2+‐Eu3+ luminescent centers by energy transfer. Tone‐tunable white light can be achieved by coupling the emission centered at 412, 541, and 612 nm contributed from Eu2+, Tb3+, and Eu3+, respectively. By adjusting the relative content of Eu2+/Tb3+/Eu3+, ideal chromaticity coordinates of (0.33, 0.33) can be achieved under excitation of ultraviolet light. High thermal stability and tiny chromaticity shift were exhibited in samples. These results suggest that Eu2+‐Tb3+‐Eu3+ tri‐activated glasses have great potential application in ultraviolet‐driven W‐LEDs. [ABSTRACT FROM AUTHOR]

Single‐composition Ba2Y2Si4O13:Bi3+,Eu3+ (BYSO:Bi3+,Eu3+) phosphors with color‐tunable and white emission were prepared by conventional high temperature solid‐state reaction method. The structural and luminescent properties of these phosphors were thoroughly investigated through X‐ray diffraction, photoluminescence, and decay curves. BYSO:Bi3+ phosphors show two excitation peaks at 342 and 373 nm, and give two emission peaks at 414 and 503 nm, respectively, indicating that there are two sites of Bi3+ in BYSO. The energy transfer from Bi3+ to Eu3+ was investigated in detail. Varied hues from blue (chromaticity coordinate [0.219, 0.350]) to white (0.288, 0.350) and orange‐red light (0.644, 0.341) can be generated by adjusting the content of Eu3+. Pure white light emission (0.311, 0.338) can be obtained under the excitation of 355 nm in BYSO:3%Bi3+,20%Eu3+ phosphor. Besides, BYSO:Bi3+,Eu3+ phosphors exhibit distinct thermal quenching properties, whose emission intensity at 473 K is 82.6% of that at 298 K. Our results indicate that BYSO:Bi3+,Eu3+ may be applied as conversion phosphors for n‐UV‐based W‐LEDs. [ABSTRACT FROM AUTHOR]

Abstract: The development of scintillators is of fundamental and industrial meaning for their diverse applications. Despite the great advance in scintillating mono‐crystals, challenge remains to search for novel scintillating materials with low cost, large volume, and high efficiency. Here, Tb3+‐doped glass ceramics (GC) with crystallized Lu6O5F8 nano‐crystals were prepared and characterized as potential X‐ray scintillators. Their structural, optical, and luminescent properties were explored systematically. After thermal treatment, X‐ray excited luminescence (XEL) intensity from Lu6O5F8:Tb3+ GC is greatly increased and the relative intensity is about 64% of commercial BGO scintillator, benefiting from preferential enrichment of Tb3+ ions into Lu6O5F8 nano‐crystals with low phonon energy. Moreover, unusual decay behaviors of Tb3+ emissions in GC sample are observed and discussed. Our results indicate that rare earth doped GC may offer a novel platform for designing and fabricating new scintillating materials in the future. [ABSTRACT FROM AUTHOR]

REEs are emerging contaminants, and soils nearby coal and coal ash with high REEs composition are vulnerable to REEs contamination. Besides, coal industry can alter surrounding soil characteristics. However, there is information paucity about REEs contamination and geochemical behaviors along with soil characteristics around coal industrial areas, which are essential for understanding their toxicity and mobilization. The study was conducted in soils surrounding Kriel coal-fired power plant (KCM) and Greenside coal mining in Witbank (GSCM), South Africa. Multivariate statistical analysis, pollution and fractionation indices, and BCR sequential extraction were applied. The ∑REEs in the soils were compared to ∑REEs abundance in the upper earth's crust (UEC), and slightly higher ∑REEs was found in KCM but slightly lower in GSCM. Generally, LREEs are abundant. The soil REEs were normalized using the Post-Archean Australian Shale (PAAS) and Eu and Gd in KCM and Gd in GSCM were >1. Contamination assessment revealed that the soils are slightly to moderately contaminated by REEs. ∑REEs in KCM was significantly correlated with soil particle sizes of 2.00–50.00 μm, Al 2 O 3 , Fe 2 O 3 , and MnO, while with 2.00–3.00 μm and Al 2 O 3 in GSCM. Fractionation characteristics showed a positive Ce anomaly, with positive linear regressions with Fe 2 O 3 and MnO. In contrast, a negative Eu anomaly was found with positive linear regressions with Al, Ca, and Mg-oxides. Oxidizable fractioned REEs accounted for 32.33% of the ∑REEs in GSCM and 35.85% in KCM, and their high EF suggests enrichment that could be due to coal mining and utilization. Most soil physicochemical properties appear to be negatively correlated with the exchangeable REEs. Overall, the soils are contaminated by REEs and the REEs characteristics are considerably influenced by major elements oxide, U, and Th contents. Therefore, more attention should be paid to REEs contamination and impacts around coal mining and utilization. [Display omitted] • Soils around coal mining and utilization are contaminated by REEs, with abundant LREEs. • Major elements oxide, U, and Th have significant effects on the REEs characteristics. • Anomalies of positive Ce and negative Eu were found in the soils. • Organic matter-bound of the soil REEs occupied substantial proportion. • Soil properties have little effects on the REEs fractionation and speciation. [ABSTRACT FROM AUTHOR]