Crystallographic and spectroscopic investigations on nine metal-rare-earth silicates with the apatite structure type

Author(s)
Maria Wierzbicka-Wieczorek, Martin Göckeritz, Uwe Kolitsch, Christoph Lenz, Gerald Giester
Abstract

Nine silicates with the apatite structure type (space group P6

3/m) containing both rare-earth elements (REEs: Pr, Nd, Sm, Tb, Ho and Er) and various metals (K, Sr, Ba and Cd) were synthesised by high-temperature flux-growth techniques and characterised by single-crystal X-ray diffraction, scanning electron microscopy, Raman spectroscopy and laser-induced photoluminescence spectroscopy. In all of the compounds, the 6h Wyckoff position is predominantly or solely occupied by REE

3+ cations, whereas the cations shows a mixed occupancy at the larger, nine-coordinate 4f site with 55-75% of REE

3+ cations and 45-25% of other metal cations. The O4 ("free" oxygen) site is fully occupied by O

2- anions, except for a Ba-Pr member with full occupancy by F

- anions. The refined formulas are Cd

2Er

8(SiO

4)

6O

2, Cd

2Tb

8(SiO

4)

6O

2, KHo

9(SiO

4)

6O

2, KTb

9(SiO

4)

6O

2, KSm

9(SiO

4)

6O

2, Sr

2Nd

8(SiO

4)

6O

2, Ba

2Nd

8(SiO

4)

6O

2, Ba

2Sm

8(SiO

4)

6O

2 and Ba

4Pr

6(SiO

4)

6F

2. Changes in the metaprism twist angle (φ) and correlations between the unit-cell parameters, average cationic radii (of M

+/M

2+-REE

3+ pairs) and the chemistry of both the synthesised M

+/M

2+-REE

3+ silicate apatites and those reported previously are evaluated. Photoluminescence measurements of undoped samples yielded emission bands in the visible region from green to red; therefore, these compounds are potential candidates for luminescent materials.

Organisation(s)
Department of Mineralogy and Crystallography
External organisation(s)
Naturhistorisches Museum Wien (NHM), Friedrich-Schiller-Universität Jena
Journal
European Journal of Inorganic Chemistry
Volume
2015
Pages
948-963
No. of pages
16
ISSN
1434-1948
DOI
https://doi.org/10.1002/ejic.201403070
Publication date
01-2015
Peer reviewed
Yes
Austrian Fields of Science 2012
104026 Spectroscopy, 104011 Materials chemistry, 105113 Crystallography
Keywords
ASJC Scopus subject areas
Inorganic Chemistry
Portal url
https://ucrisportal.univie.ac.at/en/publications/crystallographic-and-spectroscopic-investigations-on-nine-metalrareearth-silicates-with-the-apatite-structure-type(6a3c3f8e-0c59-44f2-bcf7-987d4f771947).html