Extrinsic peak in the susceptibility of incipient ferroelectric KTaO3: Li

Dielectric-constant measurements on KTaO3: Li as a function of Li concentration, temperature, and frequency reveal the presence of a peak in the susceptibility near the paraelectric anomaly at 0 K. This effect is attributed to Li impurities which are "frozen" in an off-center position at the potassium site. For samples with a Li concentration of less than 24%, continuity of the elastic compliance ensures that a lattice polarization does not occur as for a true ferroelectric. Our results support the mean-field approach to the dynamics of impurities in ferroelectric hosts. © 1978 The American Physical Society.