Characteristics and the nature of the low-frequency dielectric response in moderately concentrated KTaO3:Li

The temperature-frequency behaviour of the complex dielectric permittivity Of K0.957Li0.043TaO3 (KLT) was studied in detail. Below 250 K a pronounced relaxation-type dielectric dispersion occurs with two wide temperature maxima shifted to lower temperatures increasing in magnitude as the alternating-current monitoring frequency decreases. The results obtained are analysed by using a theory proposed considering the coupling of the TO1 soft mode (TO standing for transverse optical) to two Li relaxation modes known in moderately concentrated KLT as pi- and (pi /2)-relaxations.