Giant haven ratio for proton transport in sodium hydroxide

Solid sodium hydroxide has been prepared and investigated with respect to i ts transport properties. The proton conductivity depends significantly on t he water content, In NaOH with minimum water content (NaOH in phase equilib rium with Na2O) the proton conductivity is much lower than reported in the literature, Defect chemistry and transport characteristics are discussed, F or the same dry samples pulsed field gradient NMR revealed a surprisingly h igh H-diffusion coefficient and thus a Haven ratio of 10-10(4) in the cubic phase. In fact this value is only the lower limit since the measured condu ctivity may still be influenced by residual extrinsic effects or due to Na contributions. A cooperative mechanism is described which is able to expla in this anomaly. (C) 1999 Academic Press.