Activation energy-activation volume master plots for ion transport behavior in polymer electrolytes and supercooled molten salts.

We demonstrate the use of activation energy versus activation volume "master plots" to explore ion transport in typical fragile glass forming systems exhibiting non-Arrhenius behavior. These systems include solvent-free salt complexes in poly(ethylene oxide) (PEO) and low molecular weight poly(propylene oxide) (PPO) and molten 2Ca(NO 3 ) 2 3KNO 3 (CKN). Plots showing variations in apparent activation energy E A versus apparent activation volume V A are straight lines with slopes given by M = ΔE A /ΔV A . A simple ion transport mechanism is described where the rate determining step involves a dilatation (expressed as V A ) around microscopic cavities and a corresponding work of expansion (E A ). The slopes of the master plots M are equated to internal elastic moduli, which vary from 1.1 GPa for liquid PPO to 5.0 GPa for molten CKN on account of differing intermolecular forces in these materials.