Measurement of Na<SUB>2</SUB>O Activity in Beta-Alumina by EMF Method

Thermodynamic modeling of the (Al2O3+Na2O), (Al2O3+Na2O+SiO2), and (Al2O3+Na2O+AlF3+NaF) systems

“…A review of the data previously presented [105,106] will not be repeated here, and the explanations given by Näfe [105] and Barsoum [106] also apply to the emf studies [71,98,102,103] not mentioned by these authors. Among the emf measurement, the study of Itoh et al [97] appears to be one of the most reliable, because the authors independently measured the required data [107] for the Na reference and controlled that a symmetric cell (same mixture and electrodes on both side of the set-up) yielded a 0 emf and a cell with only a difference in the electrodes yielded the correct emf (in this case for a Pt-Mo junction). The data from Itoh et al [97] presented in figure 5 have been calculated from their experimental emf data and with the thermodynamic properties of Na 2 O (c) used in the present work.…”

“…Among the emf measurement, the study of Itoh et al [97] appears to be one of the most reliable, because the authors independently measured the required data [107] for the Na reference and controlled that a symmetric cell (same mixture and electrodes on both side of the set-up) yielded a 0 emf and a cell with only a difference in the electrodes yielded the correct emf (in this case for a Pt-Mo junction). The data from Itoh et al [97] presented in figure 5 have been calculated from their experimental emf data and with the thermodynamic properties of Na 2 O (c) used in the present work. The emf measurements from Dubreuil et al [93] with the molten salt (NaNO 2 + NaNO 3 ) as electrolyte, which should prevent the electronic conduction mentioned by Näfe [105] and insured the validity of the Nernst equation, and pure liquid Na, thus with an activity of 1, as the Na reference also appear to be reliable.…”

“…Na 2 O activity data reported in the literature [24,29,62,71,[90][91][92][93][94][95][96][97][98][99][100][101][102][103][104] are mainly derived from electrochemical measurements using galvanic cells. Näfe [105] and Barsoum [106] presented comprehensive reviews of most of the experimental data obtained by emf measurement, detailed the measuring principle, summarized the different experimental set-up and presented possible explanations for the large discrepancy observed among the different studies.…”

Electrochemical Determination of the Activity of Na2O in the Pyrochlore Phase of the Sb2O4‐NaSbO3 System

“…However, it should be possible to determine directly the concentration of antimony in the melt, with no precalibration, in the dilute solution range from the emf data if the Gibbs energies of formation of Na-␤-Al 2 O 3 and NaSbO 3 oxide phases and the ther-modynamics of the dilute antimony-containing solution (melt) are known. Although the Gibbs energy of formation of Na-␤-Al 2 O 3 has been measured by several investigators, [2][3][4][5][6][7][8][9][10][11] neither the activities of component oxides nor the free energy of formation of the interoxide phases in the Sb 2 O 4 -NaSbO 3 system are available in the literature to date. The only thermodynamic information available is the phase diagram of the Sb 2 O 4 -NaSbO 3 system established by Waring et al, 12 which is shown in Fig.…”

Preparation of Pb<SUP>2+</SUP> Ion Conducting &beta;&Prime;-Alumina and Its Application to Thermodynamic Investigation of Sulfides

“…For example, beta-alumina reacts with SOx (x=2, 3) and CO2 gases to form Na2SO4 or Na2CO3 in appropreate conditions(31) (32). The ion-exchange reaction will occur between the beta-alumina and the electrode materials even when they are solid.…”