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-β″-Al 2 O 3 -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 % Na 2 O, 0.7–0.8 wt % Li 2 O, and 89.9–92.8 wt % Al 2 O 3 , at a phase ratio β″/(β″ + β) = 0.83–1.00. Data are presented on the formation of a highly conductive β″-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 β″-alumina solid electrolytes with the compositions Na (1.53–1.73) Li (0.28–0.32) Al (10.66–10.72) O 17 and a relative density of at least 99% ranges from 25 to 33 S/m, with an activation energy for conduction Δ E a = 0.15–0.20 eV.