Performance of a miniature zirconia oxygen sensor with a Pd–PdO internal reference

A miniature zirconia oxygen sensor including the Pd–PdO mixture as an internal reference was prepared. Its performance was investigated in the wide ranges of temperature and oxygen pressure. The sensor worked well at operating temperatures above 620 K, and could precisely detect the oxygen pressure down to 10−6 atm in Ar–O2 mixtures at 723 K. The response of the sensor to the oxygen pressure change was very quick above 723 K. The sensor had a high ability to maintain a proper emf below 773 K against a little oxygen leakage into the internal reference.