44 research outputs found
Low-Temperature Structure of the Quarter-Filled Ladder Compound alpha'-NaV2O5
The low-temperature (LT) superstructure of -NaVO was
determined by synchrotron radiation x-ray diffraction. Below the phase
transition temperature associated with atomic displacement and charge ordering
at 34K, we observed the Bragg peak splittings, which evidence that the LT
structure is monoclinic. It was determined that the LT structure is
with the space group where and
represent the high temperature orthorhombic unit cell. The valence estimation
of V ions according to the bond valence sum method shows that the V sites are
clearly separated into two groups of V and V with a
charge ordering pattern. This LT structure is consistent with resonant x-ray
and NMR measurements, and strikingly contrasts to the LT structure previously
reported, which includes V sites.Comment: 4 pages, 3 figures, 1 tabl
On the Coordination Behaviour of the hmta Toward Alkali Metal Cations in Presence of Perchlorate Anions
Photoluminescent Layered Lanthanide Silicate Nanoparticles
The first examples of nanoparticles of pure layered Ln2(SiO4H)(OH)2(H2O)Cl (where Ln ) Eu, Gd,
and Tb) and mixed microcrystalline layered lanthanide silicates containing different Eu/Gd and Tb/Gd
ratios have been reported. The crystal structure of these silicates has been solved from synchrotron powder
X-ray diffraction data. These materials display interesting and tuneable photoluminescence (PL) properties,
such as energy transfer between different Ln3+ centers, illustrated here with the pairs Eu3+/Gd3+ and
Tb3+/Gd3+. The PL properties of the mixed Eu3+/Gd3+ sample change upon F– for Cl- ion exchange,
and this raises the possibility that this material may be exploited for sensing these ions