Structure and bonding characteristics of chalcogenide glasses in the system BaSeGa2Se3GeSe2

The structure of chalcogenide glasses in the system BaSeGa2Se3GeSe2 is investigated using a combination of Raman spectroscopy, 71Ga and 77Se NMR spectroscopy and neutron scattering. The results of these experiments, when taken together, indicate that the structure of these glasses consists primarily of a corner-shared network of (Ga/Ge)Se4 tetrahedra with minor edge-sharing. Homopolar metal–metal bonds are detected in glasses even with BaSe:Ga2Se3 > 1, implying violation of chemical order; however, such bonding is primarily limited to Ge atoms, in the form of GeGe bonds. A comparison between these glasses and crystalline Ba2GeSe4, of their Raman and NMR spectroscopic signatures, suggest the formation of a modified network with non-bridging Se atoms upon increasing the BaSe content. Therefore, the structure of BGGS glasses undergoes network modification characteristic of oxides as well as continuous alloying and homopolar bond formation characteristic of non-oxide chalcogenides.