Oxygen potentiometric sensors based on thermally stable solid state proton conductors: a preliminary investigation in the temperature range 150–200 °C

Potentiometric oxygen sensors based on thermally stable solid state proton conductors were expected to exhibit, at temperatures lower than 200 °C, a better performance than that of sensors based on solid state oxygen conductors. Zirconium acid phosphate (ZP) was used as thermally stable proton conductor and the study of the interface potential platinum/proton conductor versus a reference electrode Ag/AgCl, in condition of variable oxygen and water pressure in the temperature range 150–200 °C, was carried out. A linear dependence of the output potential versus the logarithm of the oxygen pressure was obtained. It was however observed that reversible electrode reactions take place in the above range of temperature only when a large interface platinum/proton conductor was used. In this case, a slope value of 24.4 mV, in good agreement with the theoretical value 23.5 mV, was found.