Phases in antiferroelectric-side Rb_1-x(ND₄)_xD₂AsO₄ crystals studied by complex permittivity

Temperature and frequency dependent dielectric measurements in the mixed ferroelectric (FE)-antiferroelectric (AFE) system Rb_1-x(ND₄)_xD₂AsO₄ (DRADA-x) (for ammonium concentrations x = 0.39, 0.55 and 0.69) are reported for measured fields along the a axis. These measurements, together with our previous light scattering results, confirm the phase coexistence of paraelectric (PE) and antiferroelectric (AFE) phases in both x = 0.55 and 0.69 crystals. Phase coexistence of deuteron-glass (DG) and antiferroelectric orderings is evidenced by the weak frequency dispersions (which occur below 100K) in both dielectric permittivities (ε′_a and ′′_a) for the x = 0.39 crystal. The temperature-dependent data ε′_a (f, T) prove the existence of an electric dipolar relaxation process below 100 K. The activation energy and attempt frequency corresponding to this relaxation process are calculated.

Keywords

• Mixed FE-AFE system,
• dielectric permittivity,
• antiferroelectric