Affiliation:
1. 1Department of Chemistry, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1
Abstract
The new germanates Ba2GeSe4−δ Teδ (δ < 2.5) were prepared by reacting the elements under exclusion of air at 800°C, followed by slow cooling to room temperature. These germanates form the Sr2GeS4 type, monoclinic space group P21/m, with lattice dimensions of a = 699.58(4), b = 709.38(4), c = 917.38(6) pm, β = 109.135(1)◦, V = 430.11(4) ・ 106 pm3 (Z = 2) for Ba2GeSe4. The structure contains isolated GeSe4 tetrahedra. The oxidation states are assigned to be BaII, GeIV, and Se−II. The yellow color of this ortho-seleno-germanate is indicative of semiconducting behavior with an activation energy of 2.6 - 3.0 eV, and the black appearance of the seleno-telluro-germanates points towards gaps < 1.7 eV. Electronic structure calculations based on the LMTO approximation resulted in smaller gaps of 1.7 - 0.8 eV, a tendency that is typical for this calculation method.
Cited by
26 articles.
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