Abstract
The dielectric behavior of undoped, lithium‐doped, and sodium‐doped polycrystalline 
was investigated as a function of frequency, from 100 Hz to 600 kHz, and temperature, over the interval from room temperature to 900°K. Barrier layer polarization seemed responsible for capacitance dispersion for undoped polycrystalline 
. These barrier layers appeared to occur at the surfaces of the individual polycrystalline grains and seemed to be the result of the chemisorption of oxygen. The data for lithium‐ and sodium‐doped 
was rationalized on the basis of a space charge polarization model involving mobile ionic point defects, which were blocked or partially blocked at the specimen electrodes, and electronic carriers, which were able to freely pass through the electrodes. The effective dielectric constant for the doped specimens varied exponentially with temperature. The activation energies of 0.6 eV for Li‐doped 
and 1.1 eV for Na‐doped 
were attributed to the energy of motion of the interstitial defect.