A novel coulometric titration setup—Principals, design and leakage minimization

• Published in: Thermochimica acta 2012-09, Vol.543, p.137-141
• Main Authors: Pishahang, Mehdi, Bakken, Egil, Stølen, Svein
• Format: Article
• Language: English
• Subjects: Chemical thermodynamics; Chemistry; Coulometric titration; electrolytes; Exact sciences and technology; General and physical chemistry; General. Theory; nitrogen; oxygen; Oxygen leakage; Oxygen non-stoichiometry; titration
• ISSN: 0040-6031; 1872-762X
• DOI: 10.1016/j.tca.2012.05.020

▸ A new coulometric titration setup is presented. ▸ The major source of error in the presented coulometric titration setup is the oxygen leakage through the YSZ solid electrolytes. ▸ The oxygen leakage through the YSZ solid electrolyte is modeled by the permeation of oxygen according to the ambipolar conductivity model. ▸ Reducing the difference in chemical potential of oxygen between the inside and the outside of the cell decreases the electrochemical leakage of oxygen into the cell. This article presents a new coulometric titration setup and describes the principles of operation, the main precautions to be taken into account to reduce the systematic errors, and evaluates the working range and the accuracy of the measurements. The major source of error, the oxygen leakage, is studied in detail and modeled based on leakage of oxygen through the YSZ solid electrolyte. Decreasing the difference in chemical potential of oxygen between inside and outside of the cell is studied as an applied measure to decrease the oxygen leakage. Flushing the pumping solid electrolyte by N2 shows a reasonable improvement. Eventually, oxygen non-stoichiometry of SrFeO3−δ is measured at 1273 K in the oxygen partial pressure range of 0.6 < −log(pO2/atm) < 12. The resulting values are in good agreement with the literature.