Influence of point defects in KTaO3 on low-temperature dielectric relaxation

Substituted KTaO3 ceramics were synthesized, sintered and studied using low-temperature microwave dielectric analysis and Raman spectroscopy. Because of a fundamentally different nature of aliovalent Mn- and isovalent Na-substitution mechanisms, significant differences in processing and dielectric properties were identified. The properties were correlated to the defect structure of the substituted KTaO3 lattices. Characteristics of the induced polar domains were clearly different for the two substitutional mechanisms, which further reflects in a significantly different dielectric behavior. Linear response of changes in the Raman spectra corresponds to evidence of the formation of symmetry-breaking regions.