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Transient electrical behavior of glass membranes

1968; Elsevier BV; Volume: 18; Issue: 4 Linguagem: Inglês

10.1016/s0022-0728(68)80004-x

2590-2954

Richard P. Buck,

Conducting polymers and applications

A fixed anionic site ion exchange model has been used to derive long-lived transient potential-distance-time profiles of ideal (surface film-free) glass membranes. The current-voltage-time curve applicable at short times for two mobile species has also been derived, and serves as a basis for the theory of membrane impedance. The potential of zero current is time-independent, while the remainder of the currentvoltage curve is time-dependent. Under a voltage pulse, the membrane current shows an initial double-layer charging spike, a decay following a t−1/2 law, and finally, establishment of a slowly varying pseudo steady state characterized by the initial d.c. resistance of the membrane modified by the mobilities of encroaching ions. The membrane steady state is not reached in a typical experiment using membranes of 30–50 μ thickness. The decomposed silica gel layer on real glass membranes is treated as a separate medium without fixed sites through which ions move by diffusion-migration to the intact glass. The current-voltage-time curve has been derived exactly by Laplace transform methods. The potential-time response at zero current after step changes in solution activity follows an exponential law in agreement with experimental data.