Rare-Earth Germanate Visible, Near-Infrared, and Up-Conversion Emitters

authors	Ananias, D; Paz, FAA; Carlos, LD; Rocha, J
nationality	International
journal	EUROPEAN JOURNAL OF INORGANIC CHEMISTRY
author keywords	Germanium; Rare earths; Lanthanides; Photoluminescence; Up-conversion
keywords	MICROPOROUS LANTHANIDE SILICATES; X-RAY PHOSPHORS; CRYSTAL-STRUCTURE; PHOTOLUMINESCENCE PROPERTIES; ABSOLUTE-CONFIGURATION; PHASE-TRANSITION
abstract	The hydrothermal synthesis and structural characterization of new trivalent rare-earth germanates, Na-4[(Y(1-a)Ln(a))(2)Ge4O13] (Ln = Eu, Tb, or Yb and Er; a = 0.05, 0.1) and Na-4[(Yb0.9Er0.1)(2)Ge4O13] are reported. The structure of these solids was solved by single-crystal X-ray diffraction (150 K). The materials crystallize in the orthorhombic non-centrosymmetric Pna2(1) space group, and exhibit a framework comprising unprecedented anionic tetrameric [Ge4O13](10-) units, tetrameric units of {GeO4} tetrahedra, and isolated dimeric units encompassing two distinct distorted {REO6} octahedra. These rare-earth germanates feature interesting photoluminescence properties in the visible and near-infrared spectral regions. Eu3+ photoluminescence confirms the presence of two distinct rare-earth sites. Energy transfer between the latter sites is shown for the Yb3+/Er3+ pair, both displaying significant near-infrared emission. Isomorphous Na-4[(Yb0.9Er0.1)(2)Ge4O13] features up-conversion emission, an unusual property among rare-earth crystalline germanates.
publisher	WILEY-V C H VERLAG GMBH
issn	1434-1948
year published	2018
issue	20-21
beginning page	2444
ending page	2451
digital object identifier (doi)	10.1002/ejic.201800153
web of science category	Chemistry, Inorganic & Nuclear
subject category	Chemistry
unique article identifier	WOS:000434220300036