Injection and migration of protons in single crystals of lithium sulphate monohydrate

Abstract

By employing a palladium-hydrogen electrode it is possible to inject protons into single crystals of Li₂SO₄H₂O. As predicted by Maricic et al. migration of protons is much preferred along the b axis of the monoclinic crystal. The current-voltage characteristics for this direction, and for the other two major directions, are interpretable in terms of space-charge-limited-currents, and, using the equations valid under such conditions the effective mobility (assumed to be field-independent) is estimated to be ca 10^–7 to 10^–8 cm² V^–1 s^–1. Lower limits for the trap concentration are in the range 10¹²–10¹³ cm^–3, and the number of effective charge carriers is about 10¹¹ cm^–3. From an examination of the structure of the solid, it is possible to formulate a plausible mechanism, based on Grotthuss conduction, for the preferred migration of the protons.