High-pressure crystallography and compression behavior of the alkali-scandium-germanate end-members LiScGe₂O₆ and NaScGe₂O₆

Author(s)

Gregor Hofer, Johann Kuzel, Katharina Sarah Scheidl, Günther J. Redhammer, Ronald Miletich-Pawliczek

Abstract

Synthetic single-crystal samples of the monoclinic pyroxene-type compounds LiScGe2O6 and NaScGe2O6 have been investigated by means of in-situ high-pressure Raman spectroscopy and X-ray diffraction techniques. Crystal-structure investigations at hydrostatic high-pressure conditions were carried out in addition to 10-4 GPa measurements using the diamond-anvil cell technique up to ~9.5 GPa. Both samples, LiScGe2O6 (space group P21/c, a=9.9999(8) Å, b=9.1040(2) Å, c=5.4610(2) Å, ß=109.240(2)° at 10-4 GPa) and NaScGe2O6 (space group C2/c, a=10.1678(5) Å, b=9.1583(5) Å, c=5.5672(3) Å, ß=107.257(3)° at 10-4 GPa), did not undergo any compression-induced change of symmetry as confirmed by single-crystal diffraction patterns. Series of high-pressure Raman spectra confirm the absence of any symmetry-related structural phase transition with band positions shifting in a smooth fashion on increasing pressure. High-precision lattice parameters, as determined from X-ray diffraction profile analyzes, were used to monitor both the compressibilities of lattice directions and the evolution of the unit-cell volume with pressure. The experimental data was fitted using a third-order Birch-Murnaghan equation-of-state approach and parameterized fits yield V0=469.60(11) Å3, K0=85.6(1.3) GPa and K'=5.9(4) for LiScGe2O6 and V0=495.95(19) Å3, K0=79(3) GPa and K'=3.9(1.1) for NaScGe2O6. The systematic comparison of volume properties and compression behavior shows that both pyroxene-type compounds follow established trend lines with similar slopes in comparing volumes versus bulk moduli, and confirm that the position of trend lines in this systematics describing variations with M1 critically depend on the type of M2 and T cations, independent on the space-group symmetry.

Organisation(s)

Department of Mineralogy and Crystallography

External organisation(s)

Eidgenössische Technische Hochschule Zürich, Paris-Lodron Universität Salzburg

Journal

Journal of Solid State Chemistry

Volume

229

Pages

188-196

No. of pages

9

ISSN

0022-4596

DOI

https://doi.org/10.1016/j.jssc.2015.06.006

Publication date

06-2015

Peer reviewed

Yes

Austrian Fields of Science 2012

104011 Materials chemistry, 105113 Crystallography

Keywords

ASJC Scopus subject areas

Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Ceramics and Composites, Materials Chemistry, Inorganic Chemistry, Physical and Theoretical Chemistry

Portal url

https://ucrisportal.univie.ac.at/en/publications/highpressure-crystallography-and-compression-behavior-of-the-alkaliscandiumgermanate-endmembers-liscge2o6-and-nascge2o6(da289a1c-adca-4882-99f8-ff0c1b00245d).html