fProton conduction and diffusion in Li₂SO₄

Both theoretical and experimental investigations on proton conduction and diffusion in Li₂SO₄ have been carried out in this work. A theoretical method has been developed based on Fick's diffusion theory to calculate the proton diffusivity under an external electric field. Using the results obtained from dc polarisation measurements the proton diffusivity has been calculated to be of the order of 10^-5 cm² s^-1 for α-Li₂SO₄. Using dc conductivity values, a calculation has been made to determine the proton concentration in the sample. The concentration obtained is of the order of 10¹⁹ to 10²⁰ cm^-3 with small structure dependence. The proton concentration is only about one percent of the Li⁺ ions, so the protons exist as an impurity in the sample. Nevertheless, these protons are very mobile, resulting in high conductivities and diffusivities.