FREQUENCY-RESPONSE STUDY OF THE KINETIC-BEHAVIOR OF NERNSTIAN SOLID-ELECTROLYTE GAS SENSORS BY PRESSURE MODULATION

A technique is described for characterizing the response behaviour of nernstian gas sensors to sinusoidal pressure modulation in the frequen cy range 0.1-1000 Hz. Relaxation times down to 0.2 ms could be resolve d for first-order kinetics. For ceria-based oxygen sensors the shape o f the spectra indicated diffusion-controlled kinetics and provided add itional information when compared with electrochemical impedance spect ra. Fast relaxation times down to 2.5 ms were found at 1173 K in air f or Pt electrodes. The pressure modulation technique avoided corrosion effects which might be induced by alternating currents and thus made i t possible to characterize the kinetics of carbonate-based CO2 sensors . Relaxation times were determined down to 4.5 ms at 973 K in air for Pd electrodes.