Formation free energy of sodium stannate measured using β-β″-AlO ceramic electrolyte.

β-β″-AlO precursor powder was successfully prepared by a solid-phase sintering method with LiCO, NaCO (as the sources of LiO and NaO, respectively) and α-AlO powder as the raw materials. The precursor was characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The results indicate that the amount of NaO in the raw materials has a great effect on the formation of β″-AlO in the β-β″-AlO precursor. When NaO content is 10 wt%, the content of β″-AlO phase reaches the maximum value of 86.24 wt% in the precursor. The β-β″-AlO ceramic was prepared from β-β″-AlO precursor powder by isostatic pressing and burying sintering process. The conductive property of the β-β″-AlO ceramic was examined by electrochemical impedance spectroscopy (EIS) method, and the density was measured by the Archimedes method. The results reveal that when 10 wt% NaO was added, the sample exhibits the best performance with the lowest resistivity of 4.51 Ω·cm and the highest density of 3.25 g·cm. A solid electrolyte battery of Pt|SnO, NaSnO|β-β″-AlO|NaCrO, CrO|Pt was assembled by the β-β″-AlO electrolyte tube to measure the open potential of the resulting battery, and the formation free energy of sodium stannate was calculated. In the temperature range of 1273-773 K, the relationship between formation free energy of sodium stannate and temperature was generated as follows: $$\Delta G_{{{\text{Na}}_{ 2} {\text{SnO}}_{ 3} }}^{0 } = - 1040.83 + 0.2221T \pm 7.54$$ . [ABSTRACT FROM AUTHOR]