- A low-temperature synthesis route for CaAlSiN3 doped with Eu2+
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A new low-temperature synthesis route of the strongly red-emitting Eu 2+ activated nitride phosphor CaAlSiN3 is presented. The fluorides CaSiF6 and AlF3 were used as a source of metal ions and Li3N as a nitrogen source. A KCN/LiCl flux system was employed to lower the temperature of the reaction from 1100 to 750 °C. The course of the reaction was studied by differential thermal analysis, and the product of the reaction was inspected by X-ray powder diffraction and luminescence measurements of CaAlSiN3:Eu. Copyright
- Kubus, Mariusz,Meyer, H.-Juergen
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- Formation and Scrolling Behavior of Metal Fluoride and Oxyfluoride Nanosheets
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We report 1-2 unit-cell-thick CaF2 nanosheets, which can be converted topochemically into LaF3-2xOx nanosheets that scroll spontaneously. The formation of CaF2 nanosheets is achieved through interlayer confinement and templating within CaSi2 during reaction with aqueous HF. The structure and morphology of these nanosheets are characterized by HRTEM, AFM, and powder XRD. Solid-state MAS and solution 19F NMR spectroscopies provide further information about interstitial fluoride sites within CaF2 nanosheets as well as help identify side products of the CaSi2 + HF reaction. CaF2 nanosheets react with lanthanide salts at room temperature to yield nanostructured hexagonal LnF3 (Ln = Ce, Pr, Nd, Sm, Eu), orthorhombic LnF3 (Ln = Gd, Dy, Ho, Er, Yb), and cubic YbF3-x products. Furthermore, the reaction of CaF2 nanosheets with lanthanum salts is unique in producing LaF3-2xOx. The evidence for this composition includes powder XRD, EDS, XPS, and 19F NMR data. The structure of LaF3-2xOx differs from hexagonal LaF3 only in the replacement of two fluorides by one oxygen. While this topochemical transformation preserves the two-dimensional morphology it also causes lattice strain that initiates scrolling. The resulting product consists of remarkable ~20 × 5 nm scroll-like tubes of LaF3-2xOx that are unique among metal fluoride materials. These results demonstrate novel metal fluoride nanochemistry and a new scrolling mechanism.
- Ramachandran, Roshini,Johnson-Mcdaniel, Darrah,Salguero, Tina T.
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