ABSTRACT
Deep red phosphors have attracted much attention for their applications in lighting, medical diagnosis, health monitoring, agriculture, etc. A new phosphor host material based on fluorine-doped lithium aluminate (ALFO) was proposed and deep red emission from Cr3+ in this host material was demonstrated. Cr3+ in ALFO was excited by blue (~410 nm) and green (~570 nm) rays and covered the deep red to near-infrared region from 650 nm to 900 nm with peaks around 700 nm. ALFO was a fluorine-doped form of the spinel-type compound LiAl5O8 with slightly Li-richer compositions. The composition depended on the preparation conditions, and the contents of Li and F tended to decrease with preparation temperature, such as Al4.69Li1.31F0.28O7.55 at 1100 °C, Al4.73Li1.27F0.17O7.65 at 1200 °C, and Al4.83Li1.17F0.10O7.78 at 1300 °C. The Rietveld analysis revealed that ALFO and LiAl5O8 were isostructural with respect to the spinel-type lattice and in a disorder-order relationship in the arrangement of Li+ and Al3+. The emission peak of Cr3+ in LiAl5O8 resided at 716 nm, while Cr3+ in ALFO showed a rather broad doublet peak with the tops at 708 nm and 716 nm when prepared at 1200 °C. The broad emission peak indicated that the local environment around Cr3+ in ALFO was distorted, which was also supported by electron spin resonance spectra, suggesting that the local environment around Cr3+ in ALFO was more inhomogeneous than expected from the diffraction-based structural analysis. It was demonstrated that even a small amount of dopant (in this case fluorine) could affect the local environment around luminescent centers, and thus the luminescence properties.
ABSTRACT
The title silver carbonate iodide, Ag10(CO3)3I4, deca-silver(I) tris-(carbonate) tetra-iodide, was recently reported as a precursor of the new superionic conductor Ag17(CO3)3I11. Ag10(CO3)3I4, was prepared by heating a stoichiometric powder mixture of AgI and Ag2CO3 at 430â K. A single-crystal suitable for X-ray diffraction analysis was obtained by slow cooling of a melt with an AgI-rich composition down from 453â K. Ag10(CO3)3I4 exhibits a layered crystal structure packed along [10], in which Ag atoms are inter-calated between the layers of hexa-gonally close-packed I atoms, and CO3 groups. Up to now, Cs3Pb2(CO3)3I is the only other compound containing carbonate groups and iodide ions registered in the Inorganic Crystal Structure Database.
ABSTRACT
A new superionic Ag+ conductor with a nominal composition Ag17(CO3)3I11 (11AgI-3Ag2CO3) was found in the AgI-Ag2CO3 system. The conductor, which was formed at temperatures from 100 to 170 °C, is a metastable phase that gradually decomposes into AgI and Ag10(CO3)I4 over a period of a few weeks at room temperature (RT). A Ag+ ionic conductivity of 0.16 S/cm was measured at RT, and an activation energy of 0.33 eV was evaluated in the temperature range from -9 to 19 °C. Single-crystal X-ray analysis revealed that Ag17(CO3)3I11 crystallized in a rhombohedral unit cell with hexagonal parameters of a = 15.8831(6) Å and c = 30.0730(13) Å at -183 °C and space group R3c. The Ag atoms were distributed over 53 sites in the asymmetry unit, with a maximum occupancy of 0.33(8). The continuous distribution of the partially occupied Ag sites was associated with the conduction paths of the Ag+ ions in the structure.
ABSTRACT
A new bending-magnet beamline with a 2.5â m normal-incidence monochromator has been constructed to serve with a light source in the visible-vacuum-ultraviolet region for photoluminescence, transmission and reflection spectroscopies of solids at the UVSOR-III 750â MeV synchrotron radiation light source. The aim is to pave the way to establishing a beamline with high photon flux, high brilliance, high energy-resolution, high linear-polarization and low higher-order light. To obtain high photon flux and brilliance, the acceptance angle of the bending-magnet radiation was designed to be 40â mrad (H) × 14â mrad (V) and the post-mirror system employed Kirkpatrick-Baez optics. The incidence angle of the incoming light to the optical elements, except to the gratings, was set to a grazing angle in order to keep a degree of linear polarization. For achieving high energy-resolution, an off-plane Eagle-type monochromator was adopted. Higher-order unwanted light in the energy range below â¼11â eV was suppressed to be less than 0.1%.
