110mAg tracer diffusion studies of CdSe–AgI–As 2Se 3 glasses

Abstract

The 110mAg tracer diffusion coefficient in the ternary (CdSe) x (AgI) 0.5 − x/2 (As 2Se 3) 0.5 − x/2 glasses decreases by two orders of magnitude with increasing x from 5.8 × 10 −9 cm 2 s −1 ( x = 0) to 5.1 × 10 −11 cm 2 s −1 ( x = 0.2) at room temperature. Simultaneously, the diffusion activation energy increases from 0.31 eV to 0.47 eV. These changes are similar to the conductivity variations and indicate that semiconducting CdSe additives are reducing the Ag + ion transport. A detailed analysis of the Haven ratio H R( x) also suggests that the CdSe-rich glasses ( x = 0.1–0.2) are mixed conductors at high temperatures. The H R( x) composition dependence shows a well-known trend for mixed cation oxide and chalcogenide glasses; the H R( x) increases with x. The last phenomenon is consistent with the proposed non-random mixing of silver and cadmium species within the preferential conduction pathways but implies immobilisation of some neighbouring Ag + cations by a Cd 2+ ion.