Structure of Na2S-GeS2 sulphide glasses - comparison with Na2O-GeO2 oxide glasses

The effect of addition of Na2S on the structure of Na2S-GeS2 sulphide glass es was investigated by XPS, IR, XRD and EXAFS measurements and discussed by comparison With that of Na2O an the structure of Na2O-GeO2 oxide glasses U nlike the change of coordination number of Ge atom from 4 to 6 in Na2O-GeO2 oxide glasses with addition of Na2O, in the case of Na2S-GeS2 sulphide gla sses, the coordination number of the Ge atom with respect to sulphur remain s 4. [GeS4] tetrahedron is the network forming unit and no occurrence of [G eS6] octahedron was observed in the Na2S-GeS2 glasses with addition of Na2S . The added Na2S is consumed in the formation of nonbridging sulphurs. The mechanism of the formation of nonbridging sulphurs and the structure of the Na2S-GeS2 glasses are modelled.