Electrochimica Acta, Vol.258, 1059-1063, 2017
Electrochemical determination of activity of Na2O in Na2Ti6O13-TiO2 two phase system between 803-1000 K
Sodium oxide (Na2O) activity in NT6-TiO2 was measured using the EMF method with test electrode Pt, Na2Ti6O13+TiO2 (NT6-TiO2). NASICON (Na2Zr2Si2PO12) was used as the solid electrolyte in conjunction with a biphasic mixture of alpha alumina (alpha-Al2O3) and sodium beta alumina (Na2O.x Al2O3) 8: 5 <= x< 11))) as the reference electrode and measurements taken over the temperature range of 803 <= T <= 1000 K. Internal consistency of the cell was ensured by approaching the equilibration target temperature from both sides, during cooling and heating. EMF measurements showed linear dependency with temperature in the temperature range under study. The activity of Na2O in NT6-TiO2 in the temperature range under study was determined. This was found to be log alpha(Na2O(NT6-TiO2))= 1: 20 - 13211/T. This data is important in the determination of theoretical EMF for the calibration electrochemical sensors employing NT6-TiO2 electrode. Furthermore, it was found that, alpha(Na2O(NT6 -TiO2)) > alpha(Na2O(NASICON)) indicating chemical stability when in contact with NASICON at higher temperatures. (c) 2017 Elsevier Ltd. All rights reserved.