Abstract
We present high energy x-ray (67 keV) and neutron scattering measurements on a single crystal of
K1−xLixTaO3 for which the Li content (x = 0.02) is less than xc = 0.022, the critical value below which
no structural phase transitions have been reported in zero field. While the crystal lattice does remain cubic down
to T = 10K under both zero-field and field-cooled (E �� 4 kV/cm) conditions, indications of crystal symmetry
lowering are seen at TC = 63K where the Bragg peak intensity changes significantly. A strong and frequencydependent
dielectric permittivity is observed at ambient pressure, a defining characteristic of relaxors. However
an extensive search for static polar nanoregions, which is also widely associated with relaxor materials, detected
no evidence of elastic neutron diffuse scattering between 300 K and 10 K. Neutron inelastic scattering methods
were used to characterize the transverse acoustic and optic phonons (TA1 and TO1 modes) near the (200)
and (002) Bragg peaks. The zone center TO1 mode softens monotonically with cooling but never reaches zero
energy in either zero field or in external electric fields of up to 4 kV/cm. These results are consistent with the
behavior expected for a dipolar glass in which the local polar moments are frozen and exhibit no long-range
order at low temperatures.