Preparation and characterization of TiO2 doped and MgO stabilized Na–β″-Al2O3 electrolyte via a citrate sol–gel method

TiO2 doped and MgO stabilized Na–β″-Al2O3 is synthesized via a citrate sol–gel method starting with Al(NO3)3, NaNO3, Mg(NO3)2 and C16H36O4Ti (tetrabutyl titanate, abbreviated as TBT). It is found that the TBT amount in the starting materials is the key factor to affect the properties of the final product, therefore, the samples sintered from precursors containing different amounts of TBT are systematically investigated by means of powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). Meanwhile, the relative density, mechanical strength and electrical properties of the prepared samples are also measured. The optimized sample contains 90.28% of β″ phase, exhibits a uniform and compact microstructure with a relative density as high as 99.5% of theoretical density (TD). In addition, this sample exhibits a bending strength up to 180 MPa and an ionic conductivity up to 0.21 S cm−1 at 350 °C.

► TiO2 doped Na–β″-Al2O3 electrolyte is synthesized via a sol–gel method with C16H36O4Ti as the precursor for TiO2.
► The optimized sample contains 90.28% of β″ phase and presents a very high relative density (99.5%).
► The optimized sample exhibits the bending strength up to 180 MPa and an ionic conductivity up to 0.21 S cm−1 (350 °C).