Time-dependent phase transformation inKTaO3:Li

After cooling below T=40 K, neutron Bragg-reflection intensities in a single crystal of ${\mathrm{KTaO}}_3$:Li, with 1.7 mol % Li atoms replacing K atoms, are observed to increase in an unusual time-dependent manner—achieving final values only after several hours, and with two characteristic times at each temperature. A ${\mathrm{KTaO}}_3$ crystal with increased Li concentration and a higher $T_c$=60 K showed similar increases in the Bragg-peak intensities with decreasing temperature, but no unusual time dependence was noted. Cooling the sample with the higher lithium content in an applied electric field suppressed the increases in intensity. The unusual time dependence of the Bragg-peak intensities observed for the sample containing 1.7 mol % Li is suggestive of behavior with some ‘‘glasslike’’ characteristics. Additionally, inelastic neutron-scattering results for this dilute sample confirm that the zone-center transverse-optical phonon is slightly hardened rather than softened by the addition of Li to ${\mathrm{KTaO}}_3$.