M. Trybuła

Coexistence of the relaxor-like and ferroelectric behavior in K1-xLixTaO3

ABSTRACT The results of low-temperature linear and nonlinear susceptibilities, polarization measurements and the dc electric field dependence of the dielectric properties of the lithium-doped potassium tantalate K1-xLixTaO3, x = 0.034 (KLT-3.4%Li) solid solution are presented. The coexistence of the relaxor-like and ferroelectric behavior and different mechanisms leading to either of them are discussed. The observed ferroelectric phase transition is of the first-order type with temperature hysteresis. This transition is due to the off-center motions of Ta ions in the octahedral environment of oxygen ions. Clusters of Li+ ions produce a relaxor-like behavior and random electric field. This field reduces the depolarization field and allows off-center motions of Ta ions and an appearance of spontaneous polarization.

K0.9982Li0.0018TaO3 Crystal Under External DC Electric Field

The influence of external dc electric field on dielectric properties of K1-xLixTaO3 x = 0.18% (henceforth KLT-x%) is presented. Electric permittivity dependence on dc electric field confirms the existence of short-range electric order. According to the suggestion made by us [1] the substitution of K+ ions by off-center Li+ in KTaO3 is considered as the source of induced polar clusters of short range order at low temperatures for this crystal. The low-temperature state of KLT-0.18 may be considered as a quantum superparaelectric one that may be toggled into an improper ferroelectric while applying an electric field [2] or a chiral glass state [3].

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.

Microwave dielectric study on CsDy(MoO4)2

Abstract Dielectric permittivity tensor ϵ11 for the multilayer crystal CsDy(MoO4)2 was determined. It was found, that at the temperature of the phase transition (45 K)ϵ22 undergoes the greatest change (δϵ22/ϵ22ϵ10%)ϵ11 shows a smaller change (δϵ11/ϵ11ϵ2%) and ϵ33, is constant over the whole range of temperatures. The anomaly is probable connected with the antiferroelectric ordering along b axis.