Solid Reference Electrode of SO₂Sensor Using Beta Alumina Solid Electrolyte

The present study was done for the purpose of finding any available solid reference electrode for SO2sensor employingbeta alumina solid electrolyte. In this paper, we tried a few experiments for this sensor using two solid reference electrode, (β+β')-alumina and (α+β)-alumina.The cells used were as follows: Pt, (β+β')-alumina in air/β'-alumina/Na2SO4/SO2+O2+SO3, Pt (1) Pt, (α+β)-alumina in air/β-alumina/Na2SO4/SO2+O2+SO3, Pt (1)(11) From the present experiments, the following conclusions were obtained.1) The constant sodium activities in these solid reference electrodes were maintained for a long duration of the experiment.2) For both cells, good straight lines were obtained between e.m.f.'s and log Pso2 within the temperature ranges from 933 to 1230 K in the cell (1) and from 932 to 1278 K in the cell (11). Especially, in the (β+β')-alumina solid reference electrode, it was shown that the cell using this electrode could be employed to determine concentrations up to a few ppm of SO2 gases at temperatures of 932 to about 1100 K. Consequently, this (β+β')-alumina mixture is recommended for the solid reference electrode ofSO2 sensor employingβ'-alumina solid electrolyte.3) From e.m.f.'s of these cells, the activities of Na2O in β-Al2O3+β'-Al2O3and α-Al2O3+β-Al2O3coexistences were respectively calculated by considering thermochemical data and compared with the others.