Two Non-Centrosymmetric Cubic Seleno-Germanates Related to CsCl-type Structure: Synthesis, Structure, Magnetic and Optical Properties

Author

Amitava Choudhury, Missouri University of Science and TechnologyFollow
Larisa A. Polyakova
Peter K. Dorhout

Abstract

Two related non-centrosymmetric, cubic, quaternary chalcogenides, containing europium have been synthesized employing the molten flux method and by the reaction of europium halides with the ternary seleno-germanate, Na₆Ge₂Se₆. The reactions of Eu, Ge and Se were accomplished in a molten Na₂Se₂ flux at 800 °C for 150 h in an evacuated fused silica ampoule and yielded Na₂EuGeSe₄ (I). Similarly, Na_0.75Eu_1.625GeSe₄ (II), could be synthesized at slightly lower temperature (750 °C) with a different starting ratio of Eu, Ge, Se and Na₂Se₂. A reaction between EuCl₃ and Na₆Ge₂Se₆ in 1:2 ratio at 650 °C for 96 h in an evacuated fused silica ampoule yielded Na₂EuGeSe₄ (I), while the reaction between EuI₂ and Na₆Ge₂Se₆ in 1:1 ratio under similar conditions yielded Na_0.75Eu_1.625GeSe₄ (II). Crystal data for these compounds are as follows: I, cubic, space group I4^‾3m (no. 217), a=7.3466(3), Z=2; II, cubic, space group I4^‾3d (no. 220), a=14.7065(8), Z=16. The crystal structures of I. and II are closely related and can be compared to a CsCl-type and its ordered superstructure, respectively. These compounds are semiconductors with optical band gaps around 2. eV. The temperature dependence of the magnetic susceptibility indicated that both compounds are paramagnetic with μ_eff.=7.6 and 7.73 μ_B, for I. and II, respectively, close to the theoretical value of 7.94 μ _B for Eu²⁺. Raman spectroscopic characterization of the compounds is also reported.

Recommended Citation

A. Choudhury et al., "Two Non-Centrosymmetric Cubic Seleno-Germanates Related to CsCl-type Structure: Synthesis, Structure, Magnetic and Optical Properties," Journal of Solid State Chemistry, vol. 180, no. 4, pp. 1381 - 1389, Elsevier, Apr 2007.

The definitive version is available at https://doi.org/10.1016/j.jssc.2007.02.002

Department(s)

Chemistry

Keywords and Phrases

Crystal Structure; Fused Silica; Magnetic Properties; Magnetic Susceptibility; Optical Properties; Synthesis (Chemical); Ternary Alloys; Chalcogenide; CsCl Type; Superstructure; Semiconducting Germanium Compounds; Chalcogenide; CsCl Type; Europium; Semiconducting; Superstructure

International Standard Serial Number (ISSN)

0022-4596

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2007 Elsevier, All rights reserved.

Publication Date

01 Apr 2007