Low temperature dielectric behavior in iron doped incipient ferroelectric KTaO₃

Abstract

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 ε′ and ε″ have been detected. Below 5 K the saturation of ε′ and ε″ takes place. It is demonstrated that low iron doped (0.01%) KTaO₃, crystals exhibit dielectric dispersion of ε′ and ε″, suggesting glass-like behavior below 5K. 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.

Key Words:

• ferroelectric
• permittivity
• iron ion
• low temperature
• glass