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Dielectric measurements in the mixed ferroelectric (FE)-antiferroelectric (AFE) system Rb1-x(ND4)xD2AsO4 (DRADA-x) (for ammonium concentrations x=0.39, 0.55, and 0.69) are reported. The phase coexistence of paraelectric (PE) and antiferroelectric (AFE) phases is confirmed in both x=0.55 and 0.69 crystals. A phase coexistence of deuteron-glass (DG) and antiferroelectric orderings is evidenced by the weak frequency dispersions (which occur below ∼ 100 K) in both dielectric permittivities (εa and ε“a) for x=0.39 crystal. The temperature-dependent data ε”a(f, T) proves the existence of an electric dipolar relaxation process forming among the antiferroelectric domains below ∼100 K.

Temperature and frequency dependent dielectric measurements in the mixed ferroelectric (FE)-antiferroelectric (AFE) system Rb1-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.