Soft-Mode Study in Li-Doped KTaO₃

Abstract

The infrared and terahertz spectra of lithium doped KTaO₃ have been studied for the first time and compared with low-frequency dielectric measurements. The frequency of the soft mode decreases on cooling and follows the tendency found by previous hyper-Raman measurements. In Li-doped crystals the mode softening is not so pronounced and therefore, the mode contribution to static dielectric constant is lower. In addition to that a typical relaxor behavior is observed in dielectric spectroscopy (10²–10⁹ Hz). The rise of the reflectivity and dielectric loss is observed below 10 cm⁻¹, which indicates presence of a central peak.

Keywords:

• Dielectric spectroscopy
• incipient ferroelectrics
• relaxor