Impedance of metal-gel derived film interface

Gel films of different compositions were grown on stainless steel and copper electrodes with varying degrees of roughness. The gel systems chosen were xM(2)O-(100-x)SiO2 (mole%) with M = Li, Na or K and x having values 10, 20 and 30 respectively. AC impedance of cells comprising the above with a counter electrode of the same type was measured over the frequency range 5 Hz to 1000 kHz. Constant Phase Angle (CPA) impedance characterizing the electrode-electrolyte interface shows a variation with frequency with the exponent n having values in the range 0.30 to 0.48. The fractal dimensions d of the electrode surfaces were determined from the self affine surface profile measurements. The ac impedance deduced n values are found to be in reasonable agreement with those calculated from the fractal dimensions of the electrode surfaces.