Ionic and electronic conduction in cuprous, argentous and aurous cyanides at high pressure

Abstract

The specific electrical conductivity σ of compacted polycrystalline CuCN, AgCN and AuCN has been measured at 320–520° K and at 10–60 kb. AgCN(I), which has a chain structure, has an activation energy E according to σ=σ₀ exp (–E/kT) which increases with increasing pressure, attributed to a predominantly ionic mechanism. For AgCN(II)(the high-pressure phase)E decreases with increasing pressure, which is consistent with a predominantly electronic mechanism for conduction. Polarization studies confirm these assignments. AuCN, which has a chain structure, shows low and high temperature regions in the graph of log σ against 10³/T, in both of which E decreases markedly with increasing pressure, and which are most likely attributable to electronic conductivity. With CuCN, which has a complex unknown structure, results differ markedly from those with AgCN and AuCN. The value of E shows a shallow minimum when plotted as a function of pressure. Thermoelectric powers with respect to Pt have also been measured for AgCN and AuCN.