GAS SENSITIVITY OF AGCL INTERFACES

In extension to the previous work on composite electrolytes, two new concepts with respect to sensor research are investigated: (a) the change of the ionic boundary conductance by using Lewis acid-base interaction between additional nucleophilic (nucleo-phobic) gases and the mobile ions in ionic conductors (here: Ag+ in AgCl); (b) the possibility of improving response time in galvanic sensors (Ag|AgCl|Cl2,Pt) by the use of composite electrolytes. As far as the first topic is concerned, the postulated space-charge effects are suggested experimentally. However, another effect mostly dominates the conductance response in polycrystal-line samples: the change of the transfer resistance due to gas adsorption in the grain boundaries. This phenomenon can, in view of reproducibility and response time, be used as a gas sensing property. The correlation with the gas partial pressure is quantitatively discussed. As regards the galvanic chlorine sensor (an example of the second concept), beneficial effects of γ-Al2O3 are investigated. The effect on the response time is more pronounced under contamination with water vapour. © 1990.