Temperature-Induced Phase Transition in a Feldspar-Related Compound BaZn₂As₂O₈∙H₂O

Author(s)

Liudmila A. Gorelova, Oleg S. Vereshchagin, Vladimir N. Bocharov, Dmitrii V. Pankin, Tamara Đorđević

Abstract

The high-temperature (HT) behavior of BaAs

₂Zn

₂O

₈∙H

₂O was studied by in situ single-crystal X-ray diffraction (SCXRD) and hot stage Raman spectroscopy (HTRS) up to dehydration and the associated phase transition. During heating, the studied compound undergoes the dehydration process with the formation of BaAs

₂Zn

₂O

₈, which is stable up to at least 525 °C. The evolution of the fourteen main Raman bands was traced during heating. The abrupt shift of all Raman bands in the 70–1100 cm

⁻¹ spectral region was detected at 150 °C, whereas in the spectral region 3000–3600 cm

⁻¹ all the bands disappeared, which confirms the dehydration process of BaAs

₂Zn

₂O

₈∙H

₂O. The transition from BaAs

₂Zn

₂O

₈∙H

₂O to BaAs

₂Zn

₂O

₈ is accompanied by symmetry increasing from P2

₁ to P2

₁/c with the preservation of the framework topology. Depending on the research method, the temperature of the phase transition is 150 °C (HTRS) or 300 °C (HT SCXRD). According to the HT SCXRD data, in the temperature range 25–300 °C the studied compound demonstrates anisotropic thermal expansion (α

_max/α

_min = 9.4), which is explained by flexible crankshaft chains of TO

₄ (T = As, Zn) tetrahedra. Additionally, we discussed some crystal-chemical aspects of minerals with both (ZnO

_n) and (AsO

_m) polyhedra (n = 4, 5, 6; m = 3, 4) as main structural units.

Organisation(s)

Department of Mineralogy and Crystallography

External organisation(s)

Saint Petersburg State University, St. Petersburg University

Journal

Minerals

Volume

12

Pages

1262-1278

No. of pages

17

ISSN

2075-163X

DOI

https://doi.org/10.3390/min12101262

Publication date

10-2022

Peer reviewed

Yes

Austrian Fields of Science 2012

104026 Spectroscopy, 105116 Mineralogy, 105113 Crystallography

Keywords

ASJC Scopus subject areas

Geology, Geotechnical Engineering and Engineering Geology

Portal url

https://ucrisportal.univie.ac.at/en/publications/f34e7381-62d4-4a32-98be-e1c4df41559c