Potentiometric SO2 gas sensor based on a thick film of Ca2+ ion conducting solid electrolyte

A planar miniaturized SO₂ sensor based upon a thick film of Ca²⁺ ion conductor-CaO·0.6MgO·6Al₂O₃ (CMA) with a Na₂SO₄ auxiliary electrode and a Pt/O₂ reference electrode was fabricated and tested. The thick film was fabricated by screen-printing CMA ink on an alumina substrate and then fired at 1823 K. The solid electrolyte was interfaced with a sodium sulphate auxiliary phase containing Pt paste and the sensor showed a good SO₂ response at 873–1073 K. The electromotive force (emf) values obtained were linearly dependent upon the logarithm values of SO₂ concentration in a range of 10–500 ppm. Both the electrodes were exposed to the same test gas thus eliminating the need to separate the electrode chambers.