Abstract
A chemical sensor using both fluoride ion conductor, PbSnF4, and silver ion conductor, Ag6I4WO4, is proposed for monitering the concentration of oxygen gas at room temperature. The sensor of the Ag/Ag6I4WO4/PbSnF4/Pt type was assembled by pressing powders of silver and the electrolytes into a pellet and by sputtering platinum thereon. The potentiometric and amperometric response characteristics were examined by measuring the electromotive force and the short-circuit current. The sensor could detect oxygen gas ranging from 0.01 to 1atm at room temperature. The 90% response time of the amperometric response, 3min on average, was 20 times shorter than that of the potentiometric one. The short-circuit current increased linearly with increasing partial pressure of oxygen, whereas the electromotive force varied directly with the logarithm of partial pressure of oxygen following a Nernst-type equation. The Nernstian slope suggested one-electron reduction of adsorped oxygen molecules on the Pt sensing electrode. The influence of humidity, the use of fast ion conductors, the preparation of PbSnF4 and the response mechanism were also reported and discussed. The sensor showed the best amperometric response characteristics among this kind of sensor reported so far. The results obtained here confirmed the utility of PbSnF4 and Ag6I4WO4 as a solid electrolyte for ambient temperature oxygen sensors.
