Dielectric dispersions in ferroelectric KD2AsO4

Abstract We have investigated the temperature and frequency dependence of the KDP-isomorphous KD2AsO4 (Curie-temperature TC =162.5 K) in the polar phase by means of dielectric measurements. In the high temperature paraphase the dielectric susceptibility ϵ33(ω) only shows the expected resonance due to the piezodistortive coupling h 36 P 3e6 in the free energy. In the ferrophase we found four distinct dispersion regimes (D1–D4) of the dielectric susceptibility within the measuring frequency range from 100 mHz to 1 GHz. Three of them are of a relaxational type, one—the remaining above mentioned dispersion — is of the resonance type. The characteristic frequencies of those dispersions are temperature dependent with different functional behaviour. Very near to the phase transition point at 162 K they can be seperated relatively well: The characteristics of the temperature dependence and evolution of the dielectric strength will be discussed leading to some evidence for the origins of the different dispersions....