Microstructure control and properties of β″-Al2O3 solid electrolyte

• β″-Al2O3 ceramics doped 0.1–0.8 wt.% TiO2 formed homogeneous and compact microstructure.
• Content of β″ phase is no less than 94%.
• The total conductivity linearly depended on the temperature and fitted well with the Arrhenius equation.
• The best bending strength and ionic conductivity obtained when the doping amount of TiO2 is 0.4wt.% and 0.8wt.%.

Doping a small amount of TiO2 can promote the relative density, increase the content of β″-Al2O3 phase and improve the microstructure of β″-Al2O3 electrolyte. In this work, the influence of microstructure, relative density, content of β″ phase and performance of β″-Al2O3 electrolyte were studied by adjusting the doping amount of TiO2 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 TiO2 can significantly improve the densification rate of β″-Al2O3 ceramics. 1500–1550 °C is the key temperature section of eliminating pore process. At 1550 °C, the sample of 0.1–0.8 wt.% TiO2 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 TiO2 was 1.6–2.0 wt.%. The total conductivity linearly depended on the temperature and fitted well with the Arrhenius equation. β″-Al2O3 ceramics showed the best bending strength and ionic conductivity at 1550 °C when the doping amount of TiO2 is 0.4 wt.% and 0.8 wt.%, respectively.

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