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The spectroscopic properties of cerium ions in various aluminosilicate glasses modified by Mg 2+ , Ca 2+ , Ba 2+ and Na + were investigated in order to optimize these for the potential utilization as Ce 3+ /Yb 3+ quantum cutting material. An increasing optical basicity of the glasses results in a shift in the peak position of the 5d-4f emission of Ce 3+ to longer wavelengths and in a decrease in the Ce 3+ fluorescence intensity due to decreasing Ce 3+ /Ce 4+ ratios. Argon-bubbling of the melt and supplying argon as melting atmosphere and/or using small amounts of metallic aluminum powder as raw material led to an almost complete reduction of Ce 4+ to Ce 3+ . This resulted in much higher intensities of the Ce 3+ fluorescence emission which runs parallel to a decreasing charge transfer absorption of Ce 4+ . From the absorption spectra of these samples extinction coefficients for Ce 4+ and Ce 3+ were calculated. For this purpose, an additional sample was prepared by using oxygen bubbling of the melt. An increasing cerium concentration shifts the Ce 3+ emission peak position to longer wavelengths, while up to 2·10 20 ions per cm 3 only a slight increase in the Ce 3+ emission intensity was observed. At higher dopant concentrations, a drastic decrease in the Ce 3+ fluorescence emission is observed which is most likely attributed to an increasing Ce 4+ concentration. High intensity Ce 3+ blue emission matching the spectroscopic requirements for potential quantum cutting in Ce 3+ /Yb 3+ codoped glasses could be achieved with a barium aluminosilicate glass.

The main goal of this work is to find natural rock materials that can be used as effective gamma rays shielding at minimal cost, reliability and wide applications. It must be at particular weight and volume (lighter and more protection). Natural bentonite clay can be used as shelters from nuclear waste because of its large availability and low cost. Bentonite clay was used in two forms naturally as it is from its ores and in ground phase. Natural bentonite was cut into cylindrical pellets at different thicknesses; also, the other form pressed into cylindrical pellets with different thicknesses and different pressing pressures (50, 100 and 150 bar). The different samples are coated with polyvinyl alcohol polymer to prevent nuclear waste leakage through porosity of clay. Chemical analysis and density are measured for all samples. Bentonite clay was found naturally in nanometer scale because it is formed from volcanic ash deposits. The nanoparticle size was determined by dynamic light scattering and Williamson-Hall size analysis using XRD patterns and the help of X-powder program. The particle size of natural bentonite was found to be 59.79 nm. The microstructure was characterized by scanning electron microscope and transmission electron microscopy. The linear and mass attenuation coefficients of nano-structured bentonite clay (natural and pressed) were determined at 662 keV energy of 137 Cs; at 1173 and 1332 keV energies of 60 Co, gamma ray sources were determined by using NaI(Tl) scintillation detector. The experimental results showed that the ground bentonite pressed at 150 bar gave the highest linear and mass attenuation coefficients than other samples. The theoretical and the experimental calculations of mass attenuation coefficient were found to be in a good agreement.

Glasses of the ternary lead-barium borate series (70−x) B 2 O 3 -30 BaO-xPbO with x = 0.05 to 30 mol% were studied for their optical properties by photoluminescence (PL) and UV-Vis absorption spectroscopy. Variations in the s-p transition of Pb 2+ were followed as variations of the lead content and varying optical basicities of the glass. The UV cutoff of the undoped glass sample is observed at about 340 nm and increasing PbO addition results in a red shift of the optical absorption edge to 480 nm for the glass with x = 30 mol%. In lead barium borate glasses, the emission intensity increases up to 4 mol% PbO before decreasing at higher PbO levels. Additionally, the series was studied regarding structural variations by Raman and infrared spectroscopy. The fraction of tetrahedrally coordinated [BO 4/2 ] − and of trigonal borate units with nonbridging oxygen atoms (metaborate and pyroborate) increases with PbO addition. The molar volume of the prepared glasses is found to increase with increasing lead content. The glass basicity, as determined from the composition, correlates well with the position of the lead excitation band. K E Y W O R D SBorate glass, Pb 2+ fluorescence, Raman spectroscopy, photoluminescence, s-p transition

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