Influence of 3d Transition Metal Doping on Lithium Stabilized Na-v"-alumina solid Electrolytes

Li-stabilized Na-v"-alumina electrolytes were doped with 3d transition metal oxides namely TiO2, Mn3O4, and NiO in order to improve their ionic conductivity and fracture strength. Due to XRD and EDX measurements, it was concluded that Mn- and Ni-ions are incorporated into the crystal lattice of Na-v"-alumina. In contrast, TiO2 doping results in the formation of secondary phases that enabled liquid-assisted sintering. All dopants increased the fracture strength of the electrolytes. 1.5 wt. % of NiO doping proved to be most efficient and lead to a maximal fracture strength of 296 MPa. Regarding the ionic conductivity, TiO2 doping showed the uppermost value of up to 0.3 S cm-1 at 300 °C. In contrast to the other dopants, TiO2 doping lowered the sintering temperature needed to obtain a dense, stable, and highly conductive Na-v"-alumina electrolyte.