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.
keywords
MICROPOROUS LANTHANIDE SILICATES; X-RAY PHOSPHORS; CRYSTAL-STRUCTURE; PHOTOLUMINESCENCE PROPERTIES; ABSOLUTE-CONFIGURATION; PHASE-TRANSITION
subject category
Chemistry
authors
Ananias, D; Paz, FAA; Carlos, LD; Rocha, J
our authors
Duarte Ananias
Assistant Researcher
Filipe Alexandre Almeida Paz
Principal Researcher
João Rocha
Full Professor
Luís Carlos
Full professoracknowledgements
We would like to thank the Fundacao para a Ciencia e a Tecnologia (FCT, Portugal) for funding. This work was developed in the scope of the project CICECO - Aveiro Institute of Materials POCI-01-0145-FEDER-007679 (Ref. FCT UID/CTM/50011/2013), financed by national funds through the FCT/MEC and when applicable, cofinanced by FEDER under the PT2020 Partnership Agreement. D. A. thanks FCT for a postdoctoral grant (SFRH/BPD/95032/2013).