Thio and selenosilicates, sulfide and selenide counterparts of silicates: similarities and differences

Thiosilicate and selenosilicate glasses are the sulfide and selenide counterparts of the well-known silicate glasses. This paper reviews the main investigations carried out to shed light on the structural, thermal and electrical characteristics of these glasses, showing their particularities compared to their oxide counterparts, such as amore complex structure with the presence of both, corner- and edge-sharing tetrahedra and much higher ion conductivity due to the larger polarizability of the chalcogen and the more covalent nature of the bonds, but also, their similarities with the presence of both, bridging and non-bridging S or Se or the existence of a mixed alkali effect when two mobile Li+ and Na+ cations coexist in the glassy network. Structural consequences of competition between SiS2 and another former, GeS2, PS5/2 or BS3/2 are also discussed.