Low temperature dielectric Behavior in iron doped incipient ferroelectric KTaO3

The dielectric spectroscopy has been applied to study low temperature behavior in the incipient ferroelectric KTaO3 doped with Fe. The measurements were performed in helium-3 cryostat. In nominally pure KTaO3 no peculiarities in the temperature-frequency behavior of electric permittivity epsilon' and epsilon" have been detected. Below 5 K the saturation of epsilon' and epsilon" takes place. It is demonstrated that low iron doped (0.01%) KTaO3 crystals exhibit dielectric dispersion of epsilon' and epsilon", suggesting glass-like behavior below 5 K. Electric permittivity dependence on dc electric field confirms the existence of short-range order. The temperature dependence of the first order non-linear dielectric permittivity was detected. Substitution the K+ ions by off-center Fe+ in KTaO3 is considered as the source of induced polar clusters of the short range order (glass or improper glass) at low temperatures for KTaO3:0.01% Fe.