Structure and ionic conductivity of a beta-alumina-based solid electrolyte prepared from sodium polyaluminate nanopowders

This paper examines the structure and transport properties of Na-beta aEuro(3)-Al2O3-based ceramic electrolytes synthesized from plasma synthesis products. The chemical composition of sodium polyaluminate nanopowders was varied in the ranges 6.5-9.3 wt % Na2O, 0.7-0.8 wt % Li2O, and 89.9-92.8 wt % Al2O3, at a phase ratio beta aEuro(3)/(beta aEuro(3) + beta) = 0.83-1.00. Data are presented on the formation of a highly conductive beta aEuro(3)-phase with a rhombohedral structure, equilibrium chemical composition, and hexagonal unit cell parameters a = 0.5587(8) nm and c = 3.342(3) nm in the system in question during sintering and annealing. The phase formation dynamics are shown to be determined by the initial composition of the powders. The 573-K ionic conductivity of beta aEuro(3)-alumina solid electrolytes with the compositions Na(1.53-1.73)Li(0.28-0.32)Al(10.66-10.72)O17 and a relative density of at least 99% ranges from 25 to 33 S/m, with an activation energy for conduction Delta E (a) = 0.15-0.20 eV.