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The Fukushima nuclear accident has highlighted the importance of finding a better final storage method for radioactive cesium species. Cs is highly soluble in water, and can easily exchange with other alkali ions in zeolites or clays to form stable complexes. However, Cs+ is released from Cs+ complexes into water when surrounded by an excess of water. Pollucite may be the best final storage option for Cs+, but its typical synthesis requires heating to about 1200°C in air. Here, we show that the hydrothermal synthesis of pollucite can be completed at 300°C in three hours from any zeolite or clay. Furthermore, our procedure does not require ion exchange before synthesis. Radioactive Cs is usually found in complexes with clays. At that time, this method only requires calcium hydroxide, water, and three hours of hydrothermal synthesis, so the process is both inexpensive and practical for large-scale application. Pollucite is an analog of analcime zeolite, and contains a channel system 2.8 Å in diameter, which is formed by 6-oxygen rings. As the diameter of Cs+ is 3.34 Å and each Cs+ exists independently within a separate portion of the channel, Cs+ cannot exit the pollucite framework without breaking it.

Ag-doped Cu 2 SiS 3 particles were prepared by the reaction of elements at 800 C for 7 days. Their crystal structure were determined from single crystal X-ray diffraction data. The solid solution limit of Ag atom into Cu atom in Cu 2 SiS 3 was estimated to be 2.0 mol % from the change of unit cell volumes. Crystal structure of 2 mol % Ag-doped Cu 2 SiS 3 was isostructure with monoclinic Cu 2 SiS 3 , superstructure of 3 times of sphalerite type. Optical absorption of above particles, whose Ag contents were from 0.0 to 3.0 mol % against to Cu, was measured by a microphone photoacoustic spectroscopy. Midpoint of main transition on Cu 2 SiS 3 particles was 499 nm (2.48 eV) and an absorption in the IR region was from 710 to 730 cm À1 corresponding to the activation energy of Cu atom bonded by S atoms. The effect of Ag addition was almost nothing up to the limit of solid solution of 2 mol % Ag, but excess Ag addition caused to a slight shift to a wide gap. So it might be consider to a photoelectric or photocatalytic application by use of sunlight.

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Shock-recovery experiments on Eu2O3 and Y2O3:Eu3+ powders using a metal plate projectile accelerated by a single-stage powder-propellant gun were performed to investigate phase stability and response at high pressures and temperatures. The recovered samples were characterized using powder X-ray diffraction analysis and photoluminescence spectroscopy. The onset of the structural phase transition from the cubic (C-type) to monoclinic (B-type) phase was observed for both Eu2O3 and Y2O3:Eu3+ powders at shock pressures of 8 and 13 GPa, respectively. For Eu2O3, the amount of B-type phase increases with increasing shock pressure up to 23 GPa, whereas for Y2O3:Eu3+, a maximum was reached at 25 GPa followed by a decrease with increasing shock pressure; only the C-type phase was detected in the sample shocked at 51 GPa. The change in the amount of B-type phase indicates stability for the monoclinic phase against shock-induced heat and mechanical deformation. The large range in shock pressure for which the C-type and B-type phases coexist in Eu2O3 and Y2O3:Eu3+ indicates that the pressure-induced phase transition is too sluggish to be completed within the shock duration. The D50→7F2/5D0→7F1 intensity ratios for the shock-recovered Eu2O3 and Y2O3:Eu3+ samples were independent of the shock pressure and the amount of C-type phase in the samples. No relationship was observed between the crystal-field parameter B20 and the amount of C-type phase in both shock-recovered samples. However, with increasing B20 2, the D50→7F2/5D0→7F1 intensity ratio decreased, whereas the D50→7F0/5D0→7F1 intensity ratio increased. These results suggest that shock-induced deformation leads to enhanced J-mixing in both the Eu2 O3 and the Y2O3:Eu3+ samples.