Electronic conduction in As 2 Se 3 , As 2 Se 2 Te and similar materials

Measurements have been made of the electrical conductivity, optical absorption and thermoelectric power of materials in the system As 2 Se 3 -As 2 Te 3 and of As 2 Se 3 . Tl 2 Te, some in the liquid and some in the glassy state. At moderate temperatures these are reasonably consistent with the behaviour of an intrinsic semi-conductor with an energy gap which becomes smaller and more diffuse with increase in temperature, in which hole conduction predominates, and in which the hole mobility varies only slightly with temperature. These conclusions are tentative; measurements of the Hall constant would yield valuable additional information. Above 650°C the behaviour of As 2 Te 3 and As 2 SeTe 2 tends to that of a liquid metal.