Dielectric-constant measurements on KTa0 3 :Li as a function of Li concentration, temperature, and frequency reveal the presence of a peak in the susceptibility near the paraelectric anomaly \t 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.

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