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The use of a small amount of MgO dopant can help to improve the performance of Na-β″-Al 2 O 3 electrolyte by enhancing the relative density, promoting the formation of homogeneous and compact microstructure, and increasing the content of β″-Al 2 O 3 phase. In this work, the effects of the amount of MgO dopant and the sintering temperature on the relative density, β″ phase content, and performance of the Na-β″-Al 2 O 3 electrolyte were studied in detail, respectively. The samples were characterized in respects of relative density, closed-cell porosity, XRD, SEM, bending strength, and AC Impedance. The results demonstrated that the addition of MgO dopant significantly improved the densification rate of Na-β″-Al 2 O 3 ceramics. The crucial temperature phase for pore elimination was 1500–1550 °C. Samples doped with 0.2–2.0 wt% MgO formed homogeneous microstructures associated with grain size refinement of the final compact at 1550 °C. Macro defects appeared when sintering temperature reached to 1580 °C. The total conductivity showed a linear dependence on the temperature (200–700 °C), which fitted well with the Arrhenius equation. Na-β″-Al 2 O 3 ceramics doped with 0.4 wt% MgO showed the best bending strength (283 MPa) and preferable ionic conductivity. [ABSTRACT FROM AUTHOR]

Doping a small amount of TiO 2 can promote the relative density, increase the content of β″-Al 2 O 3 phase and improve the microstructure of β″-Al 2 O 3 electrolyte. In this work, the influence of microstructure, relative density, content of β″ phase and performance of β″-Al 2 O 3 electrolyte were studied by adjusting the doping amount of TiO 2 and the sintering temperature. Samples were characterized with respect of density, closed-cell porosity, XRD, SEM, bending strength, AC Impedance Spectroscopy. The results demonstrated that the addition of TiO 2 can significantly improve the densification rate of β″-Al 2 O 3 ceramics. 1500–1550 °C is the key temperature section of eliminating pore process. At 1550 °C, the sample of 0.1–0.8 wt.% TiO 2 formed homogeneous microstructure associated with a refinement in the grain size of the final compact. Macro defects appeared when the sintering temperature reached to 1580 °C or the content of TiO 2 was 1.6–2.0 wt.%. The total conductivity linearly depended on the temperature and fitted well with the Arrhenius equation. β″-Al 2 O 3 ceramics showed the best bending strength and ionic conductivity at 1550 °C when the doping amount of TiO 2 is 0.4 wt.% and 0.8 wt.%, respectively. [ABSTRACT FROM AUTHOR]