NMR study of sodium ion motion in single crystal beta-alumina

The motion of sodium ions in single crystals of beta-alumina has been studied via its effects on NMR linewidth and electric quadrupole interaction. A single line is seen between −160 and +220 °C at Larmor frequencies from 4 to 19 mHz, indicating rapid ionic motion. The average coupling constant remains almost constant over the temperaure range. The average asymmetry parameter is nonzero and decreases with temperature, reflecting the change in off-axis site population. An activation energy of about 0.17 eV has been estimated from the linewidth changes in general agreement with that found from diffusion and conductivity measurements.